The Lymphatic System Part 1 Chapter 12. Lymphatic System The lymphatic system actually consists of two semi-independent parts Lymphatic vessels Transport

The Lymphatic System

Part 1

Chapter 12

Lymphatic System

The lymphatic system actually consists of two semi-independent parts• Lymphatic vessels

• Transport fluids escaped from the vascular system back to the blood

• Lymphoid tissues and organs• House the phagocytic cells and lymphocytes which

help the body's defenses against disease

Lymphatic Vessels As blood circulates throughout the body

exchanges of nutrients waste and gases occurs between the blood and the interstitial fluid.

Hydrostatic and Osmotic pressures are responsible for forcing fluid out of the blood at the capillaries and then reabsorb it into the veins

As much as 3 liters of fluid is left behind in the tissue spaces and will become part of the interstitial fluid.

Lymphatic Vessels

The fluid left behind along with plasma proteins must be carried back to the blood in order for the vascular system to have the proper amount of blood volume to operate.

If this does not occur the fluid builds up in the tissues and is then referred to as EDEMA.

Excessive edema will impair the ability of the cells to make exchanges with the interstitial fluid and eventually stop making exchanges with the blood.

Lymphatic Vessels

The function of the lymphatic vessels is to pick up the excess tissue fluid (lymph) and return it to the blood stream.

Lymph: Clear water that is found within the tissues that was not reabsorbed by the venous system.

Lymphatics: groups of lymphatic vessels that form a one way system flowing only towards the heart

Lymphatic Vessels Lymph Capillaries: form a web between the

tissue cells and the blood capillaries in the loose connective tissues of the body where they absorb leaked fluid.• Extremely permeable• Contain flap like “minivalves” along their walls that act

as one way swinging doors• When fluid pressure is higher in the interstitial space

the doors open and fluid moves into the lymphatic capillaries

• When pressure is higher inside the lymphatic vessels the flaps are forced closed and cause the fluid to be pushed along the vessel and preventing it from moving back into the interstitial space.

Lymphatic vessels

Lymph capillaries are so permeable that they can also allow proteins, cell debris and bacteria to enter and take them away from the area where they have built up.

Lymph is transported from the capillaries through the larger lymphatic vessels until it returns through one of two large ducts in the thoracic region:• Right lymphatic duct

• Thoracic duct

Lymphatic Vessels

Right Lymphatic duct:• Drains lymph from the right arm and the right

side of the head and thorax

Thoracic Duct• Receives lymph from the rest of the body

• Both ducts will empty their lymph into the subclavian vein on their side of the body

Lymphatic Vessels

Lymphatic vessels:• Thin walled

• Larger ones contain valves

• Low pressure, pumpless system

• Transported by the action of skeletal muscle contractions and pressure changes in the thorax during breathing

• The working of the smooth muscles of the digestive tract also help to move the lymph along.

Lymph Nodes

Lymph nodes:• Protect the body by removing foreign

materials such as• Bacteria

• Tumor cells

• They Produce lymphocytes which help in the immune response

Lymph Nodes

When lymph moves towards the heart it is filtered through thousands of lymph nodes that are found in clusters along the lymphatic vessels

The largest clusters of lymph nodes are found in the:• Inguinal

• Axillary

• Cervical regions

Lymph Nodes

Each lymph node contains• Macrophages: engulf and destroy bacteria,

viruses, and foreign substances so that they cannot go back into the blood stream

• Lymphocytes: type of white blood cell found in the lymph nodes also attack foreign substances

• When the lymph nodes trap the foreign substances we may become aware of the swelling of the glands.

Lymph Nodes

Lymph nodes may vary in their shape and size but most are:• Kidney shaped

• Less than 1 inch long

• Buried within the connective tissue surrounding them

• Surrounded by a fibrous capsule that contains trabeculae

Lymph Nodes

Trabeculae:• Extensions off of the fibrous capsule surrounding the

lymph node that extend inward dividing the capsule into compartments.

Cortex:• The outer part of the node which contains collections

of lymphocytes called… Follicles:

• Have a dark-staining center called germinal centers that enlarge when specific lymphocytes are generating daughter cells called plasma cells

Lymph Nodes

Plasma cells are responsible for the release of antibodies.

The rest of the cells within the cortex are lymphocytes in transit or better known as…

T-Cells• Circulate between the blood, lymph nodes

and lymphatic “stream” checking for foreign substances.

Lymph Nodes

Medulla:• Center area of the lymph node that houses the

phagocytic macrophages\

Lymph enters the convex side of the lymph node through afferent lymphatic vessels from there it flows through a number of sinuses within the lymph node and then exits the node through an indented portion known as the Hilus and then through the efferent lymphatic vessels

Lymph Nodes

There are fewer of the efferent vessels than afferent vessels which makes the flow of lymph through the lymph node is very slow.

Since it is so slow this allows the lymphocytes and macrophages to perform their cleansing and protecting functions.

It will become completely “cleansed” after passing through several lymph nodes.

Homeostatic Imbalance of the Lymph Nodes When lymph nodes become overwhelmed by

the foreign substances they are trying to destroy the nodes will become inflamed and tender to touch.

They can also become secondary cancer sites, mostly in cancers that use the lymphatic system to spread.

When the lymph nodes have cancerous tissue within them they are inflamed but do not become tender to the touch and are easily distinguished from just a viral/bacterial infection

Lymph Organs

Spleen Thymus gland Tonsils Payers patches Lymphatic tissue within the epithelial and

connective tissue

Other Lymph organs

Common feature of other lymph organs• Reticular connective tissue

• Lymphocytes

• Their function is to protect the body – only lymph nodes filter lymph

The spleen

Blood-rich organ that filters blood Location:

• Upper left side of the abdominal cavity Function:

• Filters and cleanses blood of bacteria, viruses and other debris.

• Destroys worn out red blood cells and returns their broken down products to the liver to create something else.

• Stores platelets, acts as a blood reservoir

• Produce Lymphocytes

The Thymus

Lymphatic mass that is most active during youth

Location: • Low in the throat, overlying the heart

Function:• Produces hormones that function in the

programming of lymphocytes so that they can carry out their protective role

The Tonsils

Small masses of lymphatic tissue that surround the pharynx (throat)

Location:• Found within the mucosa of the throat

Function:• Trap and remove bacteria or other foreign material

entering the body

• When they become too full of bacteria or foreign material they swell and become irritated = tonsillitis

Peyers Patches

Resemble tonsils Location:

• In the wall of the small intestine

Function:• Capture and destroy bacteria preventing it

from penetrating the intestinal wall

Mucosa-Associated-Lymphatic Tissue (MALT)

Collections of small lymphoid tissues Peyers patches and Tonsils are part of

this group MALT acts as to protect the upper

respiratory and digestive tracts from foreign matter entering those cavities

Body Defenses

Non-specific defense system:• Responds immediately to protect the body from all

foreign substances

• Provided by: • Intact skin

• Mucus membranes

• Inflammatory response

• Proteins produced by the body

Prevents entry and spread of micro-organisms through the body

Body Defenses

Specific Defense System:• Most commonly called the Immune System

• Attacks PARTICULAR foreign substances

• Its structures are • Molecules

• Immune cells

• Lymphocytes

• Macrophages

Body Defenses

Specific Defense system • When immune system is working properly it

protects us from bacteria, viruses, transplanted organs/grafts and even our own cells that have turned against us

• It does this by • Directly attacking the cells and indirectly by

releasing chemicals and protective antibodies

• Immunity: the highly specific resistance to disease

Non-Specific Body Defenses

Defined: Mechanical barriers that cover body surfaces and cells and chemicals that act to protect body from invading pathogens

Pathogen: harmful or disease causing micro-organism

Some non-specific responses to disease is inherited

Non-Specific body Defense

Surface Membrane Barriers• First line of defense against invasion of

disease causing micro-organisms• Skin

• Strong barrier of keratinized epidermis

• Produce protective chemicals

• Mucus Membranes

• Line all body cavities open to the exterior

• Produce protective chemicals

Non-Specific Body Defense

Chemicals that protect:• Acid pH of the skin

• Inhibits bacterial growth

• Sweat (sebum) contains chemicals that are toxic to bacteria

• Stomach mucosa• Secretes Hydrochloric acid and protein digesting enzymes that

kill pathogens

• Saliva and Lacrimal fluid• Contains lysozyme that destroys bacteria

• Sticky mucus• Traps micro-organisms that enter the digestive and respiratory

passages


Structural modifications that fend off invaders:• Mucus coated hairs – trap inhaled material

• Cilia – sweep dust and bacteria away from the lungs


Cells and Chemicals• The second line of defense

• These defenses rely on • Phagocytes

• Natural killer cells

• Inflammatory response

• Chemical substances

• Fever


Phagocytes:• Cell eating

• Macrophages and Neutrophils engulf the foreign particle then their cytoplasmic extensions bind the particle pulling it inside enclosing it within the vacuole

• The vacuole then fuses with the enzymatic contents of a lysosome and its contents are then broken down and digested


Natural Killer Cells• Unique group of defensive cells that can lyse and

kill cancer cells and virus infected body cells before the immune system is involved

• They can act spontaneously against any invader by recognizing certain sugars on the surface of the foreign material

• They are NOT phagocytic

• They attack the cells membrane and release chemicals that disintegrate the entire cell and its contents

Non-Specific Body defense

Inflammatory Response• Nonspecific response that is triggered whenever the

body tissues are injured

• Occurs in response to physical trauma, intense heat, irritating chemicals as well as infection of viruses and bacteria

• Four cardinal signs and symptoms of inflammation are:• Redness

• Heat

• Swelling

• Pain


Inflammatory response:• When cells are injured they release

inflammatory chemicals including histamine and kinins that:• Cause blood vessels in the involved area to dilate

and capillaries leak

• Activate pain receptors

• Attract phagocytes and white blood cells to the area (chemotaxis)


Inflammatory response:• Prevents spread of damaging agents to

nearby tissues

• Disposes of cell debris and pathogens

• Sets the stage for repair

Inflammatory Response

Within the first hour of an injury the inflammatory response occurs• Neutrophils squeeze through the capillary walls and

begin cleaning up by engulfing dead or damaged materials

• Monocytes (poor phagocytes) leave the bloodstream following the neutrophils into the inflamed area and within 8-12 hours will become macrophages with big appetites

• Macrophages take over for the neutrophils as the final disposal for cell debris

Inflammatory Response

Once the phagocytosis is finished clotting begins• Clotting proteins leak in from the blood and

close off the damaged area so that pathogens and other harmful substances cannot spread.

• This fibrous mesh also forms the “blueprint” for the permanent repair of the damaged tissue

• Local heat raises the metabolic rate of the tissue cells and speeds up the defensive action and repair processes.

Homeostatic Imbalance

If the injured area becomes severly infected a yellow pus may form in the wound

Pus: mixture of dead or dying neutrophils, broken down tissue cells and living and dead pathogens.

If the inflammatory response fails to fully clear all the debris and the sac of pus is “blocked off” it forms an Abscess that must be surgically drained before healing can take place


Antimicrobial Chemicals:• The most important antimicrobial chemicals

are the:• Complement proteins

• Interferons


Complement Proteins:• Complement: groups of at least 20 plasma

proteins that circulate in the blood in an inactive state

• Once the complement attaches itself to another material it becomes a factor in fighting foreign cells

• Complement fixation: occurs when complement proteins bind to sugars or proteins on a foreign cells surface


Complement fixation:• Membrane attack complexes: produce lesions

in the surface of a foreign cell, allowing water to rush in and cause the cell to burst

• Activated complements also amplify the inflammatory response by vasodilatation or releasing chemotaxis chemicals which draw neutrophils and macrohages to the area

• Opsonization: causes the cell membrane to become sticky and easier to phagocytize (eat)


Interferon:• Viruses cannot create ATP for energy and therefore

enter the tissues and take over the cellular “machinery” needed to reproduce themselves.

• The cell that is infected with the virus can now no longer defend itself but can help defend other cells that have not been infected yet by releasing Interpherons

• Interpherons are small proteins that diffuse to nearby cells and bind to their membrane receptors and hinder the ability of the virus to multiply within the cell

Non-Specific Body Defense Fever:

• Abnormally high body temperature• Systemic response to invading micro-organisms• Temperature is regulated by the hypothalamus and is normally set

at 98.2˚f but can be reset upwards in response to pyrogens• Pyrogens: chemicals secreted by white blood cells and

macrophages exposed to foreign cells or substances within the body

• Excessive fever is dangerous to the body but a moderate fever has benefits

• Bacteria must have large amounts of iron and zinc to multiply and during a fever the liver and spleen take up these nutrients making them less available

• Increases the metabolic rate of tissue cells speeding up their repair process

Specific Body Defenses:The Immune System

Immune response:• The immune systems response to a threat

• Increases the inflammatory response

• Provides protection targeted against specific antigens

• Initial exposure to an antigen prepares the body to react more vigorously the next time it sees it.


Immune System:• Body’s third line of defense

• Functional system that recognizes foreign molecules and acts to destroy or inactivate them

• Protects from variety of pathogens as well as abnormal body cells

• Failure of this system to work results in devastating diseases such as:

• Cancer

• AIDS

• Rheumatoid arthritis, etc.


Immunology: the study of immunity• Fairly new science

• Basis began when scientists in the early 1800’s noticed that animals who survived a serious illness had factors in their blood that protected them from getting those illnesses again

• They also found that the antibody containing serum injected into animals who had never before suffered the illness would also be protected from getting it.


Because of these scientists we found that the immune system:• Is antigen specific

• It can recognize and act against PARTICULAR pathogens or foreign substances

• Is systemic• Immunity is not restricted to the initial infection site

• Has a “memory”• It can recognize and create stronger attacks on

previously encountered pathogens


Humoral Immunity:• Also known as antibody-mediated immunity

• Provides antibodies present in the body’s own fluids (Humor’s)

Cell-mediated immunity:• When lymphocytes themselves defend the body

• Act against specific targets – virus infected cells, cancers and cells of foreign grafts

• Lymphocytes act against these targets either directly, by lysing the cell or indirectly, by releasing chemicals


Antigens:• Any substance capable of exciting our

immune system and provoking an immune response

• Large complex molecules that are not normally present in the body

• Foreign intruders to our body referred to as NONSELF

• Substances that act as antigens:• Foreign proteins, nucleic acids, large

carbohydrates, lipids


SELF antigens:• Antigens that our body can recognize

• Proteins found within the body

• They do not trigger an immune response in our body but are antigenic to other people and is the reason why our bodies reject foreign grafts unless medication or special measures are taken to cripple the immune response.


Generally small molecules are not antigenic but when combined with other proteins the immune system may not recognize the combination and attack it.

Hapten or Incomplete antigen:• The troublesome small molecule being

attacked

• Drugs and some chemicals act as haptens and cause an allergic type reaction

Cells of the Immune System

Main cells involved with the immune system are:• Lymphocytes

• B lymphocytes/B cells: produce antibodies to help with humoral immunity

• T Lymphocytes/T cells: are non-anti-body producing and are part of the cell-mediated arm of immunity

• Macrophages

• Do not respond to specific antigens but play a role in helping the lymphocytes that do.

Lymphocytes

Originate from hemocytoblasts in red bone marrow

Immunocompetent: the ability to respond to a specific antigen by binding to it.

T-Cells: originate from the lymphocytes that migrate to the thymus

B-Cells: develop in the bone marrow

Lymphocytes Once the lymphocyte is immunocompetent it can

react to one distinct antigen only because all of the antigen receptors on its surface are the same.

During their maturation process the lymphocytes become immunocompetent before they ever meet the antigens they will attack.

Our genes determine what foreign substances our immune system will be able to attack and resist.

Once the cells are immunocompetent they travel to the lymph nodes and spleen where they begin fighting the antigens and become fully mature T cells and B cells

Macrophages

Originate from monocytes formed in the bone marrow

Widely distributed throughout the lymphoid organs and connective tissues

Role: engulf foreign particles and present fragments of the antigens on their surfaces where they can be recognized by the immunocompetent t cells

Sometimes called: Antigen presenters

Macrophages

Secrete proteins called monokines Activated T-cells will release chemicals that

cause macrophages to become killer macrophages

Macrophages remain fixed in the lymphoid organs where lymphocytes circulate through the body.

The lymphocytes and macrophages must constantly communicate so that the immune system as a whole can respond to antigens

Humoral Immune Response

An immunocompetent, immature B cell/lymphocyte is stimulated to complete its maturity when an antigen binds to its surface receptor.

This event sensitizes/activates the lymphocyte to “turn on” and undergo clonal selection.• The lymphocyte multiplies rapidly and forms cells exactly

like itself with the same antigen specific receptors

• These identical cells from the same ancestor cell are clones

• Clone formation is the primary humoral response to that antigen.

Humoral Immune Response Most of these B-cell clones become plasma

cells Plasma cells: antibody producing cells produce

the same highly specific antibodies at a rate of approximately 2000 antibody molecules per second

This lasts approximately 4-5 days and then the plasma cells begin to die.

Antibody levels in the blood during this period of time peak within 10 days and then slowly decline


The B-cell clones that do not become plasma cells become longer living – memory cells

Memory cells: are capable of responding to the same antigen at later meetings with it.

They are responsible for our immunological “memory”.

This is the secondary response to antigens which is much faster, more prolonged and more effective because the preparation for an attack has already been made


Hours after the recognition of an “old-enemy” antigen new plasma cells are generated and antibodies are flowing in the blood stream

Within 2-3 days the blood antibody levels peak and they will remain high for weeks to months after.

Much faster than the initial response

Active and PassiveHumoral Immunity

Active Immunity:• When B-cells encounter antigen and produce

antibodies against them

• It is naturally acquired during bacterial and viral infections – when we develop symptoms and suffer them.

• Or they may be artificially acquired when we receive a vaccine

• Either way the body’s immune response will be the same

Active Immunity

Vaccines:• Contain dead or attenuated – living but

extremely weakened – pathogens

• There are two benefits of vaccines:• We are spared the signs and symptoms of the

disease that would occur during the primary response

• The weakened antigens are still able to stimulate antibody protection and promote an immunological memory

Active Immunity

Booster Shots:• Intensify the immune response at a later

meeting with the same antigen Vaccines:

• Fight against micro-organisms that cause pneumonia, smallpox, polio, tetanus, measles and many other diseases

• In the US a number of deadly childhood diseases have been almost completely wiped out through the use of vaccines

Passive Immunity

Antibodies are made from the serum of an immune human or animal donor.

B-cells are not challenged by the antigen and therefore immunological memory will not occur and the protection they provide will eventually disappear when the antigens die naturally

Passive Immunity

Passive immunity may occur naturally when a mother’s antibodies cross the placenta and enter fetal circulation.

The baby will be protected for several months after birth from the antigens that the mother was exposed to

It is artificially created when a person receives an immune serum or gamma globulin

Passive Immunity

Gamma globulin: Commonly administered after exposure to hepatitis

Immune serum: used to treat poisonous snake bites, rabies and tetanus because these diseases would kill a person before the active immunity could take over

Donated antibodies provide immediate protection but only survive 2-3 weeks

During this time the body’s own defenses will take over

Passive Immunity

Monoclonal antibodies:• Passive immunity antibodies prepared commercially

for use in research or diagnostic purposes.

• Produced by descendants of a single cell and exhibit specificity for only one antigen

• They can be used to deliver cancer fighting drugs to cancerous tissue or diagnosis of pregnancy, hepatitis and rabies

• They can also be used for early diagnosis and tracking the extent of cancers that are harder to find within the body

Antibodies

Also known as Immunoglobins (Igs) Make up the gamma globulin part of

blood proteins Soluble proteins secreted by activated B

cells or by their plasma cell offspring in response to an antigen

Capable of binding to that specific antigen of the B-Cell

Antibodies

Antibodies are formed in a response to many different antigens

They all contain a basic anatomy that allows them to be grouped into five Ig categories, each with a slightly different structure and function.

Basic Antibody Structure

Each antibody has a basic structure regardless of its Ig class:• Four amino acid (polypeptide) chains linked together

by disulfide bonds

• Two of the four chains are identical and contain approximately 400 amino acids each = Heavy chains

• The other two chains are identical as well but only half as long = Light chains

• When the four chains are combined the antibody molecule has two identical halves each consisting of one heavy and one light chain and the molecule as a whole is either T or Y shaped

Basic Antibody Structure Each of the four chains making up the antibody

has a variable (v) region at one end and a constant (C) region at the other which is much larger

Antibodies that respond to different antigens have different variable regions but their constant regions remain the same

The variable regions of the heavy and light chains combine to form an antigen binding site that is uniquely shaped to fit its specific antigen

Basic Antibody Structure

The constant regions form the “stem” of the antibody and performs common functions to all antibodies

They determine the type of antibody formed as well as how the antibody will carry out its immune role in the body and the cell type or chemical that it can bind with

Antibody Classes

There are five major immunoglobin classes:• IgM, IgA, IgD, IgG, and IgE (MADGE)

• IgD, IgG and IgE all have a Y shaped structure and are referred to as monomers

• IgA antibodies are found in both monomer and dimer (two linked monomers) forms

• IgM antibodies are huge and consist of five linked monomers and called pentamers

Antibody Classes

The antibody classes have slightly different roles and locations in the body.• IgG is the most abundant antibody in blood plasma

and is the only one that can cross the placental barrier

• IgM and IgG can fix complement

• IgA is found mainly in mucus and other secretions that bathe body surfaces and plays a role in preventing pathogens from getting into the body

• IgE are “troublemakers” involved in allergies by triggering the histamines that bring about an allergic response

Antibody Function

Antibodies inactivate antigens in various ways:• Complement fixation

• Neutralization

• Agglutination

• Precipitation

• Complement fixation and neutralization are the most important to body protection

Antibody Function

Complement: chief antibody ammunition used against cellular antigens such as bacteria or mismatched red blood cells

Complement is activated (fixed) during non-specific body defenses

It is also activated very efficiently when it binds to antibodies attached to cellular targets• This triggers events that result in lysis of the foreign

cell and release of molecules that enhance the inflammatory process

Antibody Function Neutralization: occurs when antibodies bind to

specific sites on bacterial exotoxins or on viruses that can cause cell injury

Agglutination: clumping of foreign cells that are bound to multiple antigens• Occurs when mismatched blood is transfused and is the

basis of tests used for blood typing Precipitation: Cross linking that involves soluble

antigenic molecules that result in large complexes that are insoluble and settle out of a solution.• Agglutinated and precipitated antigen molecules are much

more easily captured and engulfed by the body’s phagocytes than freely moving antigens

Cellular Immune Response

Like the B-cell immunocompetent T-cells are activated to form a clone by binding with a “recognized” antigen

T cells are not able to bind with Free antigens but must be presented by a macrophage and “double recognition” must occur

Macrophages engulf the antigens, process then internally and then display the parts of the processed antigen on their outer surface in combination with their own (self) protein


T-cells must recognize the “nonself” (antigen part presented by the macrophage) and also “self” by coupling with a specific glycoprotein on the macrophages surface at the same time.

This binding alone is not enough to sensitize the T-cell the macrophages must “feed” them to the T-cell

Antigen Presentation: major role of the macrophages and is essential for activation and clonal selection of t-cells


T-Cell clone classes• Cytotoxic (killer) t-cells: cells that specialize in

killing virus-infected cancer or foreign graft cells• They work by binding to them and inserting a toxic

chemical (perforin) into the foreign cells plasma membrane and shortly after the cell will rupture and die.

• Helper T-cells: T-cells that act as the “directors” or “managers” of the immune system.• Once they are activated they will circulate through the

body and recruit other cells to fight the invaders


T-cell clone classes:• Helper T-cells (continued)

• Interact directly with B-cells to provoke them to divide faster and then signal antibody formation to begin

• Release a variety of cytokine chemicals called lymphokines to indirectly rid the body of antigens by:

• Stimulating killer t-cells and B-cells to grow and divide

• Attract other types of white blood cells such as neutraphils into the area

• Enhance the ability of the macrophages to engulf and destroy micro-organisms

• Immune response gains momentum and antigens cannot fight against the immune elements acting against them


T-cell clone classes:• Suppressor T-cells: release chemicals that

suppress the activity of the T and B cells• Vital to winding down and stopping the immune response

after an antigen has been successfully activated or destroyed

• Prevents unnecessary immune system activity

• Delayed Hypersensitivity T-cells• Effector cells that play major role in cell-mediated

allergies and long-term/chronic inflammation

• When activated release lymphokines that promote an intense inflammatory response

Organ Transplants and Rejection Organ transplant can be a lifesaving treatment option

but because the immune system is so vigilant rejection can be a real problem.

There are four major types of grafts:• Autografts: tissue grafts transplanted from one site to

another in the same person

• Isografts: tissue grafts donated by a genetically identical person (related)

• Allografts: tissue grafts taken from an unrelated person

• Xenografts: Tissue grafts harvested from a different animal species.

Organ Transplants and Rejection

Autografts and Isografts are the preferred donor organ or tissue because they have a high success rate with adequate blood supply to the new organ/tissue.

Xenografts are never successful Allografts are most commonly taken from

a cadaver


When doing an alograft the ABO and other blood group antigens of both the donor and recipient must be determined and must match.

Once this is done the cell membrane antigens of the tissue cells are typed to determine how closely they will match.

At least 75% match is needed to attempt the graft – making it harder for a good tissue match between unrelated people.


Immunosuppressive therapy:• Once the transplant has been done to prevent rejection

this type of therapy must be done.

• Therapy includes:• Corticosteroids: to suppress inflammation

• Cytotoxic drugs

• Radiation therapy

• Immunosuppressor drugsWhen going through the immunosuppresive therapy it is very

hard for the body to fight against other foreign agents and the most common cause of death in these patients is a bacterial and viral infection.

Disorders of Immunity

Allergies/Hypersensitivities:• Abnormally vigorous immune responses in

which the immune system causes tissue damage as it fights off a perceived threat that would normally be harmless to the body.

• Allergen: • Type of antigen which produces the irritation


Types of Allergies:• Immediate hypersensitivity:

• Also called Acute hypersensitivity

• Triggered by the release of histamine when the IgE antibodies bind to mast cells.

• Histamine causes small blood vessels in the area to become dilated and leak and causes symptoms such as – runny nose, watery eyes, itching, etc.

• Antihistamines: anti-allergy drugs which counteract the effects of the allergen

Disorders of Immunity Anaphylactic shock:

• Acute allergic response• Occurs when the allergen directly enters the blood and

circulates quickly throughout the body• It may also follow an injection of a foreign substance in

a susceptible individual• The mechanism is the same as an allergic response

but much more life threatening because the entire body is involved – constriction of blood vessels, constriction of the bronchioles and other lung passages.

• Epinephrine is the most common and effective drug used to reverse these effects.

Disorders of Immunity Delayed Hypersensitivity:

• Take longer to appear than any of the acute reactions produced by the antibodies

• Instead of histamine the chemicals mediating these reactions are lymphokines released by activated T cells

• Corticosteroid drugs are used to provide relief of symptoms because the typical antihistamine will be useless

• Most common types of delayed hypersensitivies are:• Allergic contact dermititis: allergens that act as haptens and when

traveling through the body are perceived as foreign to the immune system causing a rash like reaction.

• Mantoux and tine tests: tests where an antigen is injected or scratched into the skin to determine if someone has been sensitized to the antigen. If not an allergic type reaction appears.

Disorders of immunity Immunodeficiencies:

• Include congenital and acquired conditions• Production or function of immune cells or complement is

abnormal.• Severe combined immunodeficiency disease (SCID): most

devastating congenital condition where there is a marked deficit of both B and T cells. Since T cells are necessary for the function of the immune system afflicted children have no protection against pathogens of any type. A simple infection or virus can be deadly to these children.• Bone marrow transplants have helped with some cases others

have survived by being behind a protective barrier constantly to keep out all infectious agents – living in a plastic “bubble”

Immunodeficiencies

Acquired Immune deficiency syndrome (AIDS): • Cripples the immune system by interfering

with the activity of helper T cells

• Most devastating of the acquired immunodeficiencies


Autoimmune Diseases:• When the immune system loses its ability to

distinguish good antigens or tolerate self antigens and attack foreign antigens.

• When this happens the body produces antibodies and sensitized T cells that attack and damage its own tissues.

• 5% of adults in North America are afflicted with autoimmune diseases – two thirds of them being women

Disorders of Immunity Autoimmune disorders:

• Multiple Sclerosis: destroys the white matter of the brain and spinal cord

• Myasthenia gravis: impairs communication between nerves and skeletal muscles

• Grave’s disease: thyroid gland produces excessive amounts of thyroxine

• Juvenile diabetes (type 1): destroys pancreatic beta cells resulting in deficient production of insulin

• Systemic Lupus erythematosus: systemic disease that occurs mainly in young females and particularly affects the kidneys, heart , lungs and skin

• Glomerulonephritis: severe impairment of kidney function• Rheumatoid arthritis: systemically destroys joints

Immune Disorders

Autoimmune diseases:• Therapies for these conditions include

treatment that depresses certain aspects of the immune response.

• Triggers for these diseases:• Inefficient lymphocyte programming: instead of

being silenced or eliminated self reactive B or T lymphocytes escape to the rest of the body. (MS)

Immune Disorders

Autoimmune diseases:• Triggers:

• Appearance of self proteins in the circulation that were previously exposed to the immune system

• Cross reaction of antibodies produced against foreign antigens with self antigens.

Developmental aspects of the Lymphatic system

Lymphatic vessels bud from the veins of the blood vascular system

Clusters of lymph nodes are obvious by the fifth week of development

Except for the thymus and spleen the lymphoid organs are poorly developed before birth

Shortly after birth these organs become heavily populated with lymphocytes as the immune system begins to function.

Developmental Aspects of the Lymphatic System

Problems with the lymphatic system are relatively rare but are usually painfully obvious:• Elephantiasis: tropical disease in which the

lymphatics become clogged with parasitic worms.

• When lymphatics are removed and severe edema is the result. Lymphatic vessels removed will grow back with time

Developmental Aspects of the Lymphatic System

Stem cells of the immune system originate in the spleen and liver during the first month of embryonic development

Later bone marrow is the predominant source of stem cells until late adult life

In late fetal life and shortly after birth the young lymphocytes develop self tolerance and immunocompetence in their programming organs and populate other lymphoid tissues

When meeting their antigens T and B cells complete their development into fully mature immune cells.

Development Aspects of the Lymphatic System

Our genes play a large role in recognizing foreign substances but our nervous system helps to control the activity of this immune response.

Because of the nervous systems large involvement of how the immune system works it can have large impacts on how well it works.• Stress will decrease the efficiency of the immune

system

• As we age the immune system becomes less efficient and the body is less able to fight foreign invaders.

Documents

The Lymphatic System Part 1 Chapter 12. Lymphatic System The lymphatic system actually consists of two semi-independent parts Lymphatic vessels Transport