• The Immune ResponseThe Immune Response• ImmunityImmunity: “Free from burden”. Ability : “Free from burden”. Ability

of an organism to recognize and defend of an organism to recognize and defend itself against itself against specificspecific pathogens or pathogens or antigens.antigens.

• Immune ResponseImmune Response: Third line of defense. : Third line of defense. Involves production of antibodies and Involves production of antibodies and generation of specialized lymphocytes generation of specialized lymphocytes against specific antigens.against specific antigens.

• AntigenAntigen: Molecules from a pathogen or : Molecules from a pathogen or foreign organism that provoke a specific foreign organism that provoke a specific immune response. immune response.

The Immune System is the Third Line of Defense Against Infection

• Innate or Genetic ImmunityInnate or Genetic Immunity: Immunity an : Immunity an organism is born with. organism is born with. Genetically determined.Genetically determined. May be due to lack of receptors or other molecules May be due to lack of receptors or other molecules

required for infection.required for infection. Innate human immunity to canine distemper.Innate human immunity to canine distemper. Immunity of mice to poliovirus.Immunity of mice to poliovirus.

• Acquired ImmunityAcquired Immunity:Immunity that an :Immunity that an organism organism developsdevelops during lifetime. during lifetime. Not genetically determined.Not genetically determined.

May be acquired naturally or artificially.May be acquired naturally or artificially. Development of immunity to measles in response to infection or Development of immunity to measles in response to infection or

vaccination.vaccination.

• Types of Acquired ImmunityTypes of Acquired Immunity• I. Naturally Acquired ImmunityI. Naturally Acquired Immunity: Obtained : Obtained

in the course of daily life.in the course of daily life.– A. Naturally Acquired Active ImmunityA. Naturally Acquired Active Immunity: : AntigensAntigens or pathogens enter body naturally. or pathogens enter body naturally. Body generates an immune response to antigens.Body generates an immune response to antigens. Immunity may be lifelong (chickenpox or mumps) or Immunity may be lifelong (chickenpox or mumps) or

temporary (influenza or intestinal infections).temporary (influenza or intestinal infections).

– B. Naturally Acquired Passive ImmunityB. Naturally Acquired Passive Immunity: : AntibodiesAntibodies pass from mother to fetus via placenta or breast pass from mother to fetus via placenta or breast

feeding (feeding (colostrumcolostrum).). No immune response to antigens.No immune response to antigens. Immunity is usually Immunity is usually short-livedshort-lived (weeks to months). (weeks to months). Protection until child’s immune system develops.Protection until child’s immune system develops.

• Types of Acquired Immunity (Continued)Types of Acquired Immunity (Continued)• II. Artificially Acquired ImmunityII. Artificially Acquired Immunity: Obtained by : Obtained by

receiving a vaccine or immune serum.receiving a vaccine or immune serum.– 1. Artificially Acquired Active Immunity1. Artificially Acquired Active Immunity: : AntigensAntigens are introduced in vaccines ( are introduced in vaccines (immunizationimmunization). ). Body generates an immune response to antigens.Body generates an immune response to antigens. Immunity can be lifelong (oral polio vaccine) or temporary (tetanus Immunity can be lifelong (oral polio vaccine) or temporary (tetanus

toxoid).toxoid).

– 2. Artificially Acquired Passive Immunity2. Artificially Acquired Passive Immunity: : Preformed Preformed antibodiesantibodies ( (antiserumantiserum) are introduced into body by ) are introduced into body by

injection. injection. Snake antivenom injection from horses or rabbits.Snake antivenom injection from horses or rabbits.

Immunity is short lived (half life three weeks).Immunity is short lived (half life three weeks). Host immune system does not respond to antigens.Host immune system does not respond to antigens.

SerumSerum: Fluid that remains after blood has clotted : Fluid that remains after blood has clotted and cells have been removed.and cells have been removed.

AntiserumAntiserum: Serum containing antibodies to a : Serum containing antibodies to a specific antigen(s). Obtained from injecting an specific antigen(s). Obtained from injecting an animal (horse, rabbit, goat) with antigen (snake animal (horse, rabbit, goat) with antigen (snake venom, botulism or diphtheria toxin).venom, botulism or diphtheria toxin).

SerologySerology: The study of reactions between antibodies : The study of reactions between antibodies and antigens.and antigens.

Gamma GlobulinsGamma Globulins: Fraction of serum that contains : Fraction of serum that contains most of the antibodies.most of the antibodies.

Serum SicknessSerum Sickness: Disease caused by multiple : Disease caused by multiple injections of antiserum. Immune response to foreign injections of antiserum. Immune response to foreign proteins. May cause fever, kidney problems, and proteins. May cause fever, kidney problems, and joint pain. Rare today.joint pain. Rare today.

ANATOMY OF THE IMMUNE SYSTEM

• The immune system is localized in several parts of the body– immune cells develop

in the primary organs - bone marrow and thymus (yellow)

– immune responses occur in the secondary organs (blue)

ANATOMY OF THE IMMUNE SYSTEM• Thymus – glandular organ near the heart – where T cells learn

their jobs

• Bone marrow – blood-producing tissue located inside certain bones– blood stem cells give rise to all of the different types of blood cells

• Spleen – serves as a filter for the blood– removes old and damaged red blood cells

– removes infectious agents and uses them to activate cells called lymphocytes

• Lymph nodes – small organs that filter out dead cells, antigens, and other “stuff” to present to lymphocytes

• Lymphatic vessels – collect fluid (lymph) that has “leaked” out from the blood into the tissues and returns it to circulation

Antibodies are Produced by B Lymphocytes

Antibodies are Proteins that Recognize Specific Antigens

• AntigensAntigens Most are Most are proteinsproteins or large or large polysaccharidespolysaccharides from from

a foreign organism.a foreign organism. MicrobesMicrobes: Capsules, cell walls, toxins, viral capsids, flagella, : Capsules, cell walls, toxins, viral capsids, flagella,

etc.etc. NonmicrobesNonmicrobes: Pollen, egg white , red blood cell surface : Pollen, egg white , red blood cell surface

molecules, serum proteins, and surface molecules from molecules, serum proteins, and surface molecules from transplanted tissue. transplanted tissue.

Lipids and nucleic acids are only antigenic when Lipids and nucleic acids are only antigenic when combinedcombined with proteins or polysaccharides. with proteins or polysaccharides.

Molecular weight of 10,000 or higher.Molecular weight of 10,000 or higher. HaptenHapten: Small foreign molecule that is not antigenic. Must be coupled : Small foreign molecule that is not antigenic. Must be coupled

to a to a carriercarrier molecule to be antigenic. Once antibodies are formed they molecule to be antigenic. Once antibodies are formed they will recognize hapten.will recognize hapten.

• AntigensAntigens• EpitopeEpitope: : Small part of an antigen that interacts Small part of an antigen that interacts

with an antibody.with an antibody. Any given antigen may have several Any given antigen may have several

epitopes.epitopes. Each epitope is recognized by a different Each epitope is recognized by a different

antibody.antibody.

• AntibodiesAntibodies Proteins Proteins that recognize and bind to a particular that recognize and bind to a particular

antigen with very high antigen with very high specificityspecificity.. Made in response to exposure to the antigen.Made in response to exposure to the antigen. One virus or microbe may have several One virus or microbe may have several antigenic antigenic

determinant sitesdeterminant sites, to which different antibodies , to which different antibodies may bind.may bind.

Each antibody has at least two identical sites Each antibody has at least two identical sites that bind antigen: that bind antigen: Antigen binding sitesAntigen binding sites..

Valence of an antibodyValence of an antibody: Number of antigen : Number of antigen binding sites. Most are binding sites. Most are bivalentbivalent..

Belong to a group of serum proteins called Belong to a group of serum proteins called immunoglobulins (Igs).immunoglobulins (Igs).

• How Do B Cells Produce How Do B Cells Produce Antibodies?Antibodies? B cells develop from B cells develop from stem cellsstem cells in the bone marrow of in the bone marrow of

adults (liver of fetuses).adults (liver of fetuses). After maturation B cells migrate to lymphoid organs After maturation B cells migrate to lymphoid organs

(lymph node or spleen). (lymph node or spleen). Clonal SelectionClonal Selection: When a B cell encounters an antigen it : When a B cell encounters an antigen it

recognizes, it is stimulated and divides into many clones recognizes, it is stimulated and divides into many clones called called plasma cellsplasma cells, which actively secrete antibodies., which actively secrete antibodies.

Each B cell produces antibodies that will recognize only Each B cell produces antibodies that will recognize only one antigenic determinant.one antigenic determinant.

• ApoptosisApoptosis Programmed cell death (“Falling away”).Programmed cell death (“Falling away”). Human body makes 100 million lymphocytes every day. Human body makes 100 million lymphocytes every day.

If an equivalent number doesn’t die, will develop If an equivalent number doesn’t die, will develop leukemia.leukemia.

B cells that do not encounter stimulating antigen will self-B cells that do not encounter stimulating antigen will self-destruct and send signals to phagocytes to dispose of their destruct and send signals to phagocytes to dispose of their remains.remains.

Many virus infected cells will undergo apoptosis, to help Many virus infected cells will undergo apoptosis, to help prevent spread of the infection.prevent spread of the infection.

Consequences of Antibody Binding

Protection Against Invading Pathogens1. First Line of Defense: Non-specific natural

barriers which restrict entry of pathogen.

Examples: Skin and mucous membranes.

2. Second Line of Defense: Innate non-specific immune defenses provide rapid local response to pathogen after it has entered host.

Examples: Fever, phagocytes (macrophages and neutrophils), inflammation, and interferon.

3. Third line of defense: Antigen-specific immune responses, specifically target and attack invaders that get past first two lines of defense.

Examples: Antibodies and lymphocytes.

First Line of Defense:Skin and Mucous Membranes

I. Mechanical Defenses

1. Skin has two Layers:

A. Epidermis: Thin outer layer of epithelial tissue.

Contains Langerhans cells, dead cells, and keratin (waterproof).

B. Dermis: Thick inner layer of connective tissue.

Infections are rare in intact skin. Exceptions:• Hookworms can penetrate intact skin• Dermatophytes: “Skin loving” fungi

Intact Skin is an Effective Barrier Against Most Pathogens

I. Mechanical Defenses

2. Mucous Membranes: Line gastrointestinal, genitourinary, and respiratory tracts.

– Two layers: Outer epithelial and inner connective layer.

– Epithelial layer secretes mucus which maintains moist surfaces.

– Although they inhibit microbial entry, they offer less protection than skin.

– Several microorganisms are capable of penetrating mucous membranes:

• Papillomavirus

• Treponema pallidum

• Enteroinvasive E. coli• Entamoeba histolytica

I. Mechanical Defenses 3. Lacrimal apparatus: Continual washing and

blinking prevents microbes from settling on the eye surface.

4. Saliva: Washes microbes from teeth and mouth mucous membranes.

5. Mucus: Thick secretion that traps many microbes.

6. Nose Hair: Coated with mucus filter dust, pollen, and microbes.

7. Ciliary Escalator: Cilia on mucous membranes of lower respiratory tract move upwards towards throat at 1-3 cm/hour.

I. Mechanical Defenses 8. Coughing and sneezing: Expel foreign

objects.

9. Epiglottis: Covers larynx during swallowing.

10. Urination: Cleanses urethra.

11. Vaginal Secretions: Remove microbes from genital tract.

B. Chemical Defenses:

– Sebum: Oily substance produced by sebaceous glands that forms a protective layer over skin. Contains unsaturated fatty acids which inhibit growth of certain pathogenic bacteria and fungi.

– pH: Low, skin pH usually between 3 and 5. Caused by lactic acid and fatty acids.

– Perspiration: Produced by sweat glands. Contains lysozyme and acids.

– Lysozyme: Enzyme that breaks down gram-positive cell walls. Found in nasal secretions, saliva, and tears.

B. Chemical Defenses (Continued)– Gastric Juice: Mixture of hydrochloric

acid, enzymes, and mucus. pH between 1.2 to 3 kills many microbes and destroys most toxins. Many enteric bacteria are protected by food particles.

• Helicobacter pylori neutralizes stomach acid and can grow in the stomach, causing gastritis and ulcers.

– Transferrins: Iron-binding proteins in blood which inhibit bacterial growth by reducing available iron.

II. Second Line of Defense1. Phagocytosis: Derived from the Greek words “Eat and cell”. – Phagocytosis is carried out by white blood cells:

macrophages, neutrophils, and occasionally eosinophils.

– Neutrophils predominate early in infection.– Wandering macrophages: Originate from

monocytes that leave blood and enter infected tissue, and develop into phagocytic cells.

– Fixed Macrophages (Histiocytes): Located in liver, nervous system, lungs, lymph nodes, bone marrow, and several other tissues.

Phagocytic Cells: Macrophages (Monocytes), Neutrophils, and Eosinophils

(Macrophages)

Process of Phagocytosis

• Inflammation • Triggered by tissue damage due to infection,

heat, wound, etc. • Four Major Symptoms of Inflammation:• 1. Redness• 2. Pain• 3. Heat• 4. Swelling• May also observe:• 5. Loss of function

• Functions of Inflammation • 1. Destroy and remove pathogens

• 2. If destruction is not possible, to limit effects by confining the pathogen and its products.

• 3. Repair and replace tissue damaged by pathogen and its products.

Stages of Inflammation1. Vasodilation: Increase in diameter of blood

vessels.

Triggered by chemicals released by damaged cells: histamine, kinins, prostaglandins, and leukotrienes.

2. Phagocyte Migration and Margination: Margination is the process in which phagocytes stick to lining of blood vessels.

Diapedesis (Emigration): Phagocytes squeeze between endothelial cells of blood vessels and enter surrounding tissue.

Process of Inflammation

Stages of Inflammation (Continued)

Phagocytes are attracted to site of infection through chemotaxis.

Phagocytes destroy microbes, as well as dead and damaged host cells.

3. Tissue Repair: Dead and damaged cells are replaced.

Antimicrobial Substances: I. Complement System: Large group of serum

proteins that participate in the lysis of foreign cells,

inflammation, and phagocytosis.

Two mechanisms of complement activation:

1. Classical Pathway: Initiated by an immune

reaction of antibodies.

2. Alternative Pathway: Initiated by direct

interaction of complement proteins with microbial

polysaccharides.

Both pathways cleave a complement protein called

C3, which triggers a series of events.

Both Classical and Alternative Complement Pathways Trigger the Cleavage of C3

II. Interferons: Antiviral proteins that interfere with viral multiplication.

– Small proteins (15,000 to 30,000 kDa)– Heat stable and resistant to low pH– Important in acute and short term infections.– Have no effect on infected cells.– Host specific, but not virus specific.

Interferon alpha and beta: Produced by virus infected cells and diffuse to neighboring cells. Cause uninfected cells to produce antiviral proteins (AVPs).

Interferon gamma: Produced by lymphocytes. Causes neutrophils to kill bacteria.

Natural killer cells (NK cells)

• instead of attacking the invaders, they attack the body’s own cells that have become infected by viruses

• they also attack potential cancer cells, often before they form tumors

• they bind to cells using an antibody “bridge”, then kill it by secreting a chemical (perforin) that makes holes in the cell membrane of the target cell. With enough holes, the cell will die, because water rushing inside the cell will induce osmotic swelling, and an influx of calcium may trigger apoptosis.

Mast cells

• are found in tissues like the skin, near blood vessels.

• are activated after antigen binds to a specific type of antibody called IgE that is attached to receptors on the mast cell.

• activated mast cells release substances that contribute to inflammation, such as histamine.

• mast cells are important in allergic responses but are also part of the innate immune response, helping to protect from infection.

Structures of the Immune SystemStructures of the Immune System

• Unlike other body systems, Immune System is NOT contained within a single set of organs or vessels

• Action depends on structures from lymphatic, cardiovascular, and Integumentary systems

• Works primarily through antigen-antibody reaction

Organs of The Immune System

The organs of the immune system are stationed throughout the body.

They are known as lymphoid organs because they are concerned with the growth, development, and deployment of lymphocytes white blood cells that are key operatives of the immune system.

Functions of the Lymph SystemFunctions of the Lymph System

• lymph/o• drain fluid from tissue spaces and return to

it to the blood• transport materials (nutrients, hormones

and oxygen) to body cells• carry away waste products to the blood • transport lipids away from digestive system• control of infection

Adenoid

Tonsil

Lymphnodes

Spleen

Peyer’s patches(small intestine)

Appendix

Lymphaticvessels

Masses oflymphocytes and

macrophages

Tissuecells

Lymphaticvessel

Bloodcapillary

LymphaticcapillaryInterstitial

fluid

Lymphnode

• The lymphatic system– Plays an active role in defending the body from

pathogens Interstitial fluid bathing the tissues, along with the white blood cells in it, continually enters lymphatic capillaries.

1

Figure 43.5

Fluid inside thelymphatic capillaries,called lymph, flowsthrough lymphaticvessels throughout

the body.

2

Within lymph nodes,microbes and foreignparticles present in the circulating lymph

encounter macro-phages, dendritic cells,

and lymphocytes, which carry out

various defensive actions.

3

Lymphatic vesselsreturn lymph to theblood via two large

ducts that drain intoveins near the

shoulders.

4

Lymph SystemLymph System

• Lymph originates in blood plasma

• Interstitial fluid• cleans and nourishes body

tissues• collects cellular debris,

bacteria• return to blood or lymph

capillaries

Lymphoid organs

• Peripheral – remove and destroy antigens in the blood and lymph– Tonsils– Lymph nodes– Spleen– Intestinal lymphoid tissues

• Central – site of maturation of cells– Thymus– Bone marrow

Lymphatic SystemLymphatic System

• Major structures– lymph vessels– lymph nodes– lymph fluid– tonsils

• Also– spleen– thymus

Lymph capillaries

• Closed-ended vessels

• Lined by endothelium

• 1-way flaps into capillary– Allows passage of tissue fluid,

large proteins, bacteria, viruses, cancer cells, cell debris

Lymph capillaries

• Found in all areas of blood capillaries except:– Bone, teeth, bone marrow, CNS

• Lacteals – lymph capillaries in villi of small intestine transports fat (chyle) [compare with blood capillaries]

Lymphatic Vessels

• Lymphatic Collecting Vessels– Receive lymph from lymphatic capillaries– Have the same 3 tunics as veins, but:

• Are thinner, have more internal valves, and anastomose more

• Lymphatic Trunks– Formed from the union of the largest of the

lymphatic collecting vessels– Drain large areas of the body

Lymphatic Vessels

• Lymphatic Ducts– 2 vessels that receive lymph from lymphatic trunks

• Right Lymphatic Duct– Drains lymph from the right upper arm and the right side of the

head and the thorax

– Empties into the vascular system at the junction of the right internal jugular vein and right subclavian vein

• Thoracic Duct– Drains lymph from the left upper arm, left side of the head and

thorax, and digestive organs, pelvis, and legs

– Much larger

– Empties into the vascular system at the junction of the left internal jugular vein and left subclavian vein

Lymph NodesLymph Nodes

• located in lymph vessels

• small round or oval structures (filters)

• depositories for cellular debris

• bacteria and debris phagocytized

Lymph NodesLymph Nodes

• inside are masses of tissue which contain WBCs (lymphocytes)

• almost always grouped 2 or 3 to 100

• invading cells destroyed in nodes and often swell as an indicator of the disease process

Lymph Node Function• Multiple afferent lymphatic vessels enter a lymph at its hilus - the indented region on the concave side

• Lymph percolates thru the node and it is scrutinized by macrophages and lymphocytes ready to mount an immune response

• Lymph leaves via a few efferent lymphatic vessels

• Lymph usually has to pass thru several nodes before it is “clean”

Lymph ducts

• Thoracic (L) lymphatic duct– Drains ¾ of lymph– L head, neck, thorax, upper

extremity– R&L abdomen, lower

extremities

• Right lymph duct– R head, neck, thorax, upper

extremity

• Ducts drain into subclavian veins 20.6a

Spleen• Largest

lymphoid organ. About the size of a fist.

• Location:– Left side of the

abdominal cavity, just beneath the diaphragm and curling around the anterior stomach

• Served by the splenic artery and vein which enter at its hilus

• Surrounded by a fibrous CT capsule with inward extending trabeculae

• Functions include:– Extracting old & defective RBCs and removal of debris and foreign matter

from blood– Storage of blood platelets and iron

• Internal structure consists of:– White Pulp

• Smaller portion• Islands of lymphocytes and reticular fibers

– Red Pulp• Venous sinuses and splenic cords (regions of reticular fibers and

macrophages)

Spleen• Functional tissue:

• White pulp– Lymphocytes around

central arteries– Immune response to

antigens– Produces both B & T

lymphocytes

Spleen• Red pulp

– Splenic cords• Lymphocytes • Reticular fibers• Macrophages• Cleanse blood• Remove old rbcs

TonsilsTonsils

• masses of lymph tissue designed to filter tissue fluid, not lymph

• located beneath certain areas of moist epithelium exposed to outside and hence to contamination

• any or all may become so loaded with bacteria that the pathogens gain dominance

• should not be removed unless absolutely necessary.

Tonsils

• Form a ring of lymphoid tissue around the entrance to the pharynx

• 3 main sets:– Palatine

• Located on either side of the posterior oral cavity

• Largest and infected most often

– Lingual• Lie at the base of the

tongue

– Pharyngeal • Found in the posterior

wall of the nasopharynx• Called adenoids when

infected

Tonsils

20.12

• Aggregations of lymphocytes and lymph nodules

• MALT – mucosa associated lympoid tissue

Thymus• Found in inferior neck and anterior thorax• Secretes hormones that allow T lymphocyte maturation• Prominent in newborns, it increases in size throughout childhood.

In adolescence, it begins to atrophy and is fatty/ fibrotic in adults.• Only lymphoid organ that does not fight antigens

ThymusThymus

• lymphatic tissue

• mediastinum

• primary role: changes lymphocytes to T cells for cellular immunity

Features of Immune SystemFeatures of Immune System Self/Non self recognitionSelf/Non self recognition Immunological specificityImmunological specificity

B and T cells zero in on certain kinds of B and T cells zero in on certain kinds of pathogens; response is pathogen specificpathogens; response is pathogen specific

DiversityDiversity Immunological memoryImmunological memory

Immune system recognizes and reacts swiftly Immune system recognizes and reacts swiftly to a pathogen it has “seen”to a pathogen it has “seen”

Cells and tissues of the immune system

Pluripotential hematopoietic stem cells Located within the bone marrow, fetal liver

and yolk sac of the fetus Stem cells differentiate into 2 types of

“committed” stem cells produce platelets, erythrocytes (red blood cells),

monocytes or granulocytes. produces cells of the lymphoid line only

Cells and Tissues of the Immune System

Cells of the immune system are found within the blood, body tissues, thymus, spleen, liver, lymph nodes and body areas exposed to the external environment.

These organs comprise the reticuloendothelial system (RES).

Lymphocyte Activation

B Cell FormationB Cell Formation

Derived from stem cells in bone marrowDerived from stem cells in bone marrow Acquire unique antigen-binding Acquire unique antigen-binding

receptors in marrowreceptors in marrow Receptors interact with just one antigenReceptors interact with just one antigen Exposure to that antigen causes clonal Exposure to that antigen causes clonal

selection selection Division of cells specific for that antigenDivision of cells specific for that antigen

T Lymphocytes (T cells)

Derived from stem cells in the bone marrow. Leave bone marrow and travel to the thymus

to mature Approximately 75 to 80% of lymphocytes are

T cells. Important in recognizing foreign material that

is fixed in the tissues of cells.

T Lymphocytes (T cells)

Play an important role in regulating the production of antibodies by B cells Helper T cell Suppressor T cell Killer or Killer T cells

T cells have surface proteins known as cluster determinants (CDs) Helper T cells are CD4 positive cells enhance and promote the

action of other immune cells. Suppressor T cells are CD8 positive and have suppressive or

cytotoxic effects

Composition of Human Blood

Cellular Elements of BloodCell Type # Cells/mm3 FunctionErythrocytes (RBC) 4.8-5.4 million Transport O2 and CO2

Leukocytes (WBC) 5000-9000 Various A. Granulocytes: 1. Neutrophils (70% of WBC) Phagocytosis 2. Basophils (1%) Produce histamine 3. Eosinophils (4%) Toxins against parasites

some phagocytosis

B. Monocytes/Macrophages (5%) Phagocytosis

C. Lymphocytes (20%) Antibody production (B cells) Cell mediated immunity (T

cells)

Platelets 300,000 Blood clotting

Blood

• hem/o and hemat/o• plasma - 55%• formed elements - 45%• serum - plasma without clotting

proteins

Blood Cells

• RBC - erythrocytes - erythropoiesis

• WBC - leukocytes - leukopoiesis

• Platelets - thrombocytes - thrombopoiesis

Erythrocytes

• erythr/o - red• cyte - cell• Hemoglobin - blood

protein transports oxygen• Reticulocyte - immature

erythrocyte • RBCs produced by red

bone marrow

Leukocytes

• leuk/o - white• Protect the body

against invasion• Pass through

capillary walls

• Granulocytes– neutrophils (phagocytosis)

– eosinophils (allergies)

– basophils (promote inflammation)

• Agranulocytes– lymphocytes (production of circulating

antibodies)

– monocytes (macrophages)

• Collection of dead and living bacteria and leukocytes called pus, abscess.

Lymphocytes

• T cells or T Lymphocytes– mature in thymus gland– Cell mediated immunity

• B cells or B Lymphocytes– mature in bone marrow– antibody-mediated

immunity

Thrombocytes

• smallest formed element• made in bone marrow• essential to blood coagulation• If injury, blood comes in contact with any tissue other

than the lining of the vessels, platelets stick together, form plug, seals wound. Chemicals released, series of reactions, formation of clot.

Plasma

• plasma– 92% water– 8% plasma proteins

• albumin• globulin• fibrinogen

• serum - plasma without clotting proteins or fibrinogen

Functions of the Immune System

Functions of the Immune System

• To protect the entire body from a variety of harmful substances– pathogenic microorganisms– allergens– toxins– malignant cells