BY: Edelia Vazquez, Karina Delacruz, Marisol Lopez, and Rudy Garcia

Ms. Guillory’s Anatomy and Phy. H class. p. 2

Your immune system protects you from many infections. When a foreign organism enters your body, your immune system recognizes the invading organism, and destroys it in order to protect you. Most people's immune system

protects them from the flu.

Defense against infectious organisms and other invaders; thus the immune response

Enables your body to know the difference between yourself and outside germs.◦ They communicate with each other

Two important tasks are: Killing and remembering, by recognizing foreign invaders◦ Equipped with to recognize the invaders

The Pathogens release chemicals and proteins that our immune defense recognizes, triggering the kill response

Communicate with signals that stimulate them to produce antibodies Stick with invaders in order for killing cells to recognize the pathogens

Parts of the Immune System

Lymphoid Organs:◦ A fibrous connective tissue capsule separates lymphoid organs from

surrounding tissues. These Organs include the lymph nodes, the thymus, and the spleen.

Lymph Nodes:◦ Small, oval lymphoid organs ranging in a diameter from 1 to 25 mm◦ Filters and purifies lymph before that fluid reaches the venous circulation◦ As lymph flows through a lymph node, at least 99 percent of the antigens in the lymph are removed◦ Fixed macrophages in the walls of the lymphatic sinuses engulf debris or pathogens in lymph as it

flows past◦ Antigens removed in this way are then processed by the macrophages and “presented” to nearby

lymphocytes. Thymus:

◦ Lives in your chest◦ Located between the sternum and heart◦ Most important in New Born Babies◦ Without it, the body would just die◦ As to in Humans/Adults the thymus can be removed and will be no problem◦ Produces T-cells:

They are used to help measure the immune system’s health

◦ The thymus produces several hormones that are important to the development and maintenance of normal immunological defenses.

The Spleen:• The adult spleen contains the largest collection of lymphoid tissue in the body• In gross dissection, the spleen is deep red owing to the blood it contains• Functions of spleen:

• 1.) The removal of abnormal blood cells and other blood components by phagocytosis • 2.) the storage of iron from recycled red blood cells • 3.) the initiation of immune responses by B-cells and T-cells in response to antigens in circulating blood

White Blood cells • Most important part in the immune system• Big collection of other cells working together to eliminate viruses and bacteria• Types of leukocytes:

• lymphocytes, Eosinophils, basophils, monocytes, and neutrophils

Antibodies:o Any of numerous Y-shaped protein molecules produced by B-cells as a primary immune defenseo each molecule and its clone having a unique boning site that can combine with the complementary site for a foreign antigen, as on a virus or bacterium, thereby disabling the antigen and signaling other immune defenses.

PParts of the Immune arts of the Immune System System continued continued

Epidermis:◦ The outer, nonvascular, nonsensitive layer of the skin, covering the true

skin or corium◦ Skin provides protection from foreign invaders

Apart from physical barrier there are specialized cells of the immune system throughout the layers of skin

Some of these cells detect invasion by foreign proteins such as bacteria or viruses and other cells have the function of destroying and removing such material

Mechanical removal ◦ is the process of physically flushing microbes from the body. Methods include:

a. mucus and cilia Mucus traps microorganisms and prevents them from reaching and colonizing the mucosal

epithelium. Mucus also contains lysozyme to degrade bacterial peptidoglycan, an antibody called secretory Ig, that prevents microbes from attaching to mucosal cells and traps them in the mucus, lactoferrin to bind iron and keep it from being used by microbes, and lactoperoxidase to generate toxic superoxide radicals that kill microbes. Cilia on the surface of the epithelial cells propels mucus and trapped microbes upwards towards the throat where it is swallowed and the microbes are killed in the stomach. This is sometimes called the tracheal toilet.

b. the cough and sneeze reflex Coughing and sneezing removes mucus and trapped microbes.

c. vomiting and diarrhea These processes remove pathogens and toxins in the gastrointestinal tract.

d. the physical flushing action of body fluids Fluids such as urine, tears, saliva, perspiration, and blood from injured blood vessels also

flush microbes from the body.

The human body has multiple defense mechanisms, but these can be sorted into two general categories:◦ 1.) Nonspecific defenses do not distinguish one type of threat

from another. Their response is the same, regardless of the type of invading

agent. These defenses, which are present at birth, include physical barriers, phagocytic cells, immunological surveillance, interferon's, complement, inflammation, and fever. They provide a defensive capability known as nonspecific resistance.

◦ 2.) Specific Defenses protect against particular threats. For example, a specific defense may protect against infection by one type of bacterium but ignore other bacteria and viruses. Many specific defenses develop after birth as a result of accidental or deliberate exposure to environmental hazards. Specific defenses depend on the activities of lymphocytes. The body’s specific defenses produce a state of protection known as immunity, or specific resistance.

There are 7 nonspecific defenses:1.Physical barriers keep hazardous organisms and materials outside the body. For example, a mosquito that lands on your head may be unable to reach the surface of the scalp if you have a full head of hair.2.Phagocytes are cells that engulf pathogens and cell debris. Examples of phagocytes are the macrophages of peripheral tissues and microphages of blood.3.Immunological surveillance is the destruction of abnormal cells by NK cells in Peripheral tissues. 4.Interferon's are chemical messengers that coordinate the defenses against viral infection.5.Complement is a system of circulating proteins that assist antibodies in the destruction of pathogens.6.The inflammatory response is a local response to injury or infection that is directed at the tissue level. Inflammation tends to restrict the spread of an injury as well as combat an infection.7.Fever is an elevation of the body temperature that accelerates tissue metabolism and defenses.

Specific resistance, or immunity, is provided by the coordinated activities of T cells and B cells, which respond to the presence of specific antigens. The basic functional relationship can be summarized as follows:

1. T cells are responsible for cell-mediated immunity (or cellular immunity), our defense against abnormal cells and pathogens inside cells.

2. B cells provide antibody – mediated immunity (or humoral immunity), our defense against antigens and pathogens in body fluids.

Both mechanisms are important, because they come into play under different circumstances. Activated T cells do not respond to antigenic materials in solution, and the antibodies produced by activated B cells cannot cross cell membranes. Moreover, helper T cells play a crucial role in antibody-mediated immunity by stimulating the activity of B cells.

Immunity is either innate or acquired. Innate Immunity

Innate Immunity is genetically determined; it is present at birth and has no relationship to previous exposure to the antigen involved. For example , people do not get the same diseases goldfish do. Innate Immunity breaks down only in the case of AIDS or other conditions that depress all aspects of specific resistance.

Acquired Immunity

Acquired Immunity is not present at birth; you acquire immunity to a specific antigen only once you have been exposed to that antigen. Acquired Immunity can be active or passive. Active Immunity appears after exposure to an antigen, as a consequence of the immune response. The Immune system is capable of defending against a large number of antigens. The appropriate defenses are mobilized only after you encounter a particular antigen. Active acquired immunity can develop as a result of (1) natural exposure to an antigen in the environment (naturally acquired immunity) or (2) from deliberate exposure to an antigen (induced active immunity). Naturally acquired immunity normally begins to develop after birth, and it is continually enhanced as you encounter “new” pathogens or other antigens. The purpose of induced active immunity is to stimulate antibody production under controlled conditions so that you will be able to overcome natural exposure to the pathogen some time in the future. This is the basic principle behind immunization, or vaccination, to prevent disease. A vaccine is a preparation that contains either a dead or an inactive pathogen or antigens derived from that pathogen. Vaccines are designed to induce an immune response.

Passive Immunity

Naturally passive immunity are antibodies acquired from the mother. Induced passive immunity works by an injection of antibodies. For example, antibodies that attack the rabies virus are injected into a person bitten by a rabid animal.

Immunity exhibits four general properties: (1) specificity, (2) versatility, (3) memory, and (4) tolerance.

Specificity

A specific defense is activated by a specific antigen, and the immune response targets that particular antigen and no others. Specificity results from the activation of appropriate lymphocytes and the production of antibodies with targeted effects.

Versatility

Millions of antigens in the environment can pose a threat to health. Over a normal lifetime, an individual encounters only a fraction of that number, perhaps tens of thousands of antigens. The Immune system has no way of anticipating which antigens it will encounter. It must be ready to confront any antigen at any time. Versatility results in part from the large diversity of lymphocytes present in the body and in part from variability in the structure of synthesized antibodies.

Memory

The Immune System “remembers” antigens that it encounters. As a result of this memory, the Immune Response that occurs after a second exposure to an antigen is stronger and lasts longer than the response to the first exposure.

Tolerance

The Immune system does not respond to all antigens. For example, all cells and tissues in the body contain some antigens that normally fail to stimulate an immune response. The Immune System is said to exhibit tolerance toward such antigen.

When an antigen triggers an immune response, it usually activates both T cells and B cells. The activation of T cells, which usually occurs first, involves active phagocytes exposed to the antigen. Once activated, T cells attack the antigen and stimulate the activation of B cells. Activated B cells mature into cells that produce antibodies; antibodies distributed in the bloodstream bind to and attack the antigen.

T cells and cell – mediated Immunity

T cells play a key role in the initiation, maintenance, and control of the immune response.

Three major types of T cells include:1. Cytotoxic T cells (TC), which are responsible for cell mediated immunity.

They enter peripheral tissues and directly attack antigens physically and chemically.

2. Helper T Cells (TH), Which stimulate the responses of both T cells and B cells. They are absolutely vital to the immune response, because B cells must be activated by the helper T cells before B cells can produce antibodies.

3. Suppressor T cells (TS), which inhibit T cell and B cell activities and moderate the immune response.

T cell ActivationBefore an immune response can begin, T cells must be activated by exposure

to an antigen. This activation seldom happens by direct lymphocyte-antigen interaction, and foreign compounds or pathogens entering a tissue commonly fail to stimulate an immediate immune response.

T cells only recognize antigens that are bound to glycoprotein's in cell membranes

Antigen Presentation:

Also called cluster of differentiation markers:◦ in T cell membranes◦ molecular mechanism of

antigen recognition◦ more than 70 types:

designated by an identifying number

CD3 Receptor Complex

Found in all T cells

CD8CD8 Markers Markers Found on cytotoxic T cells and

suppressor T cells Respond to antigens on Class

I MHC proteins

◦ CD4 Markers Found on helper T cells Respond to antigens on Class II

MHC proteins CD8 or CD4 Markers - Bind to CD3

receptor complex Prepare cell for activation

Costimulation For T cell to be activated, it must be

costimulated:◦ by binding to stimulating cell at

second site◦ which confirms the first signal

2 Classes of CD8 T Cells Activated by exposure to antigens on

MHC proteins:◦ one responds quickly:

producing cytotoxic T cells and memory T cells

◦ the other responds slowly: producing suppressor T cells

Figure 22–17 (Navigator)

Also called killer T cells Seek out and immediately

destroy target cells

1. Release perforin:◦ to destroy antigenic cell membrane

2. Secrete poisonous lymphotoxin:◦ to destroy target cell

3. Activate genes in target cell:◦ that cause cell to die

Slow ResponseCan take up to 2 days from time of first

exposure to an

antigen, for cytotoxic T cells to reach effective levels

Memory Tc Cells Produced with cytotoxic T cells Stay in circulation Immediately form cytotoxic T cells:

◦ if same antigen appears again

Suppressor T Cells Suppressor T Cells Secrete suppression factors Inhibit responses of T and B

cells After initial immune

response Limit immune reaction to

single stimulus

Figure 22–18

Helper T Cells - Activated CD4 T cells divide into:

active helper T cells:secrete cytokines

memory T cells:remain in reserve →↓←←←←←←←←

4 functions of Cytokines

1. Stimulate T cell divisions:produce memory T cellsaccelerate cytotoxic T cell

maturation2. Attract and stimulate

macrophages3. Attract and stimulate NK

cells4. Promote activation of B

cells

Figure 22–19

Cell-mediated immunity involves close physical contact between activated Tc cells and foreign, abnormal or infected cells

T cell activation usually involves:◦antigen presentation by phagocytic cell◦costimulation by cytokines from active

phagocytes Tc cells may destroy target cells through local

release of cytokines, lymphotoxins, or perforin

Responsible for antibody-mediated immunity Attack antigens by producing specific antibodies Millions of populations, each with different

antibody molecules

B Cell Sensitization Corresponding antigens in interstitial fluids bind

to B cell receptors B cell prepares for activation Preparation process is sensitization

Figure 22–20 (Navigator)

During sensitization, antigens are:

taken into the B cell, processed,reappear on surface, bound to Class II MHC protein

Sensitized B cell is prepared for activation, but needs helper T cell activated by same antigen

B Cell Activation Helper T cell binds to MHC complex:

◦ secretes cytokines that promote B cell activation and division

B Cell Division Activated B cell divides into:

◦ plasma cells -Synthesize and secrete antibodies into interstitial fluid

Memory B cells- Like memory T cells remain in reserve to respond to next infection

Figure 22–21a, b

What is the structure of an antibody, and what types of antibodies are found in body fluids and secretions

2 parallel pairs of polypeptide chains: ◦ 1 pair of heavy chains ◦ 1 pair of light chains

Each chain contains:◦ constant segments ◦ variable segments-Determine

specificity of antibody molecule

•Antigen–Antibody Complex = An antibody bound to an antigen

2 parallel pairs of polypeptide chains: ◦ 1 pair of heavy chains ◦ 1 pair of light chains

Each chain contains:◦ constant segments ◦ variable segments-Determine specificity of antibody molecule

5 Heavy-Chain 5 Heavy-Chain Constant Segments

Determine 5 types of antibodies:◦ IgG◦ IgE◦ IgD◦ IgM◦ IgA

Free tips of 2 variable segments:◦ form antigen binding sites of antibody molecule◦ which bind to antigenic determinant sites of antigen molecule

Antibody Function

A Complete Antigen A Complete Antigen Has 2 antigenic determinant sites Binds to both of antigen binding sites of variable segments of antibody Exposure to a complete antigen leads to:

◦ B cell sensitization◦ immune response

A Hapten A Hapten Also called partial antigen Must attach to a carrier molecule to act as a complete antigen Dangers of Haptens Antibodies produced attack both hapten and carrier molecule If carrier is “normal”:

◦ antibody attacks normal cells◦ e.g., penicillin allergy

Also called immunoglobins (Igs) Are found in body fluids Are determined by constant segments Have no effect on antibody specificity

7 Functions of Antigen–Antibody Complexes

1. Neutralization of antigen binding sites2. Precipitation and agglutination:

◦ formation of immune complex3. Activation of complement4. Attraction of phagocytes5. Opsonization:

◦ increasing phagocyte efficiency6. Stimulation of inflammation7. Prevention of bacterial and viral adhesion

Antibody-mediated immunity involves the production of specific antibodies by plasma cells derived from activated B cells

B cell activation usually involves:◦ antigen recognition, through binding to surface

antibodies, costimulation by a Th cell Antibodies produced by active plasma cells bind to

target antigen and:◦ inhibit its activity or destroy it◦ remove it from solution◦ promote its phagocytosis by other defense cells

Figure 22–22

Occur in both cell-mediated and antibody-mediated immunity

First exposure:◦ produces initial

response (Primary) Next exposure:

◦ triggers secondary response

◦ more extensive and prolonged

◦ memory cells already primed

Takes time to develop Antigens activate B cells Plasma cells differentiate Antibody titer slowly rises Peak response:

◦ can take 2 weeks to develop◦ declines rapidly

IgM:◦ is produced faster than IgG◦ is less effective

The Secondary ResponseThe Secondary Response Activates memory B cells:

◦ at lower antigen concentrations than original B cells

◦ secrete antibodies in massive qualitiesEffects of Memory B Cell Activation

IgG:◦ rises very high and very quickly◦ can remain elevated for extended

time IgM:

◦ production is also quicker◦ slightly extended

Immunization produces a primary response to a specific antigen under controlled conditions

If the same antigen appears at a later date, it triggers a powerful secondary response that is usually sufficient to prevent infection and disease

Figure 22–23

Specific and nonspecific defenses

Figure 22–24

Figure 22–25

Neutrophils and NK cells begin killing bacteria Cytokines draw phagocytes to area Antigen presentation activates:

◦ helper T cells◦ cytotoxic T cells

B cells activate and differentiate Plasma cells increase antibody levels

Combined Responses to Viral Infection

Similar to bacterial infection But cytotoxic T cells and NK cells are activated by contact with

virus-infected cells

Table 22–2

Viruses replicate inside cells, whereas bacteria may live independently Antibodies (and administered antibiotics) work outside cells, so are primarily effective

against bacteria rather than viruses Antibiotics cannot fight the common cold or flu T cells, NK cells, and interferons are the primary defense against viral infection

Immune System developmentImmune System development Fetus can produce immune response or immunological competence:

◦ after exposure to antigen◦ at about 3–4 months

Development of Development of Immunological CompetenceImmunological Competence

Fetal thymus cells migrate to tissues that form T cells Liver and bone marrow produce B cells 4-month fetus produces IgM antibodies

Maternal IgG antibodies:◦ pass through placenta◦ provide passive immunity to fetus

After Birth Mother’s milk provides IgA antibodies:

◦ while passive immunity is lost

Normal Resistence:Normal Resistence: Infant produces IgG antibodies through exposure to antigens Antibody, B-cell, and T-cell levels slowly rise to adult levels:

◦ about age 12

1. Interleukins2. Interferons3. Tumor necrosis factors4. Chemicals that regulate phagocytic activities5. Colony stimulating factors6. Miscellaneous cytokines

Autoimmune disorders- A malfunction of system that recognizes and ignores “normal” antigens

Activated B cells make autoantibodies against body cells Immunodeficiency disease-

Thyroiditis Rheumatoid arthritis Insulin-dependent diabetes mellitus Allergies –

Immunodeficiency Diseases Immunodeficiency Diseases 1. Problems with embryological development of lymphoid tissues:

◦ can result in severe combined immunodeficiency disease (SCID)

2. Viral infections such as HIV:◦ can result in AIDS

3. Immunosuppressive drugs or radiation treatments:◦ can lead to complete immunological failure

Inappropriate or excessive immune responses to antigens Allergens:

◦ antigens that trigger allergic reactions

4 Categories of Allergic Reactions4 Categories of Allergic Reactions Type I:

◦ immediate hypersensitivity Type II:

◦ cytotoxic reactions Type III:

◦ immune complex disorders Type IV:

◦ delayed hypersensitivity

Also called immediate hypersensitivity A rapid and severe response to the presence of an antigen Most commonly recognized type of allergy Includes allergic rhinitis (environmental allergies) Sensitization leads to:

◦ production of large quantities of IgE antibodies ◦ distributed throughout the body

Second exposure leads to:◦ massive inflammation of affected tissues

Type I Allergy (2)Type I Allergy (2) Severity of reaction depends on:

◦ individual sensitivity◦ locations involved

Allergens in blood stream may cause anaphylaxis

Can be fatal Affects cells throughout body Changes capillary permeability:

◦ produce swelling (hives) on skin Smooth muscles of respiratory system contract:

◦ make breathing difficult Peripheral vasodilatation:

◦ can cause circulatory collapse (anaphylactic shock)

Antihistamine DrugsAntihistamine Drugs Block histamine released by MAST cells Can relive mild symptoms of immediate hypersensitivity

Stress and the Immune Response Stress and the Immune Response Glucocorticoids:

◦ secreted to limit immune response ◦ long-term secretion (chronic stress):

inhibits immune response lowers resistance to disease

Depression of the inflammatory response Reduction in abundance and activity of phagocytes Inhibition of interleukin secretion

Aging and the Immune ResponseAging and the Immune ResponseImmune system deteriorates with age, increasing vulnerability to infections

and cancer

4 Effects of Aging on Immune 4 Effects of Aging on Immune ResponseResponse

1. Thymic hormone production:◦ greatly reduced

2. T cells:◦ become less responsive to antigens

3. Fewer T cells reduce responsiveness of B cells 4. Immune surveillance against tumor cells declines

Figure 22–27

Nervous and Endocrine Systems Interact with thymic hormonesAdjust sensitivity of immune

The relationship among the cells of the Immune response and the nervous and endocrine systems are now the focus of intense research.

For examples, the cells of the immune system can influence central nervous system (CNS) and endocrine activity.

3 categories affect immune response:◦ disorders resulting from:

an insufficient immune response an inappropriate immune response an excessive immune response

Before vaccines were invented the only way to create immunity in the body was to suffer through a bout of the disease in question. Once endured, providing you survived, your immune system could fight off any future infections before they took hold. B-cells in the bloodstream, responsible for fighting off the disease, retain memory of the disease. If the disease returned, the immune system launched a quick attack before the disease could take hold. When people get vaccinated:

Vaccination is inserted into body, it is “basically” the disease or “sickness” in a more weakened form. Once inserted, the body examines the new substance that is found in the body and therefore protects immunity. In the future, in case you get sick, the body and the immune system are prepared to fight it off and prevent you

from getting sick.

All vaccinations work by presenting a foreign antigen to the immune system in order to evoke an immune response, there are several ways to do so. The four main types that are currently in clinical use are as follows: An inactivated vaccine consists of virus particles which grown in culture and then killed using a method

such as heat or formaldehyde In an attenuated vaccine, live virus particles with very low virulence are

Administered. They will produce, but very slowly. Virus-like particle vaccines consists of viral protein(s) derived from the structural

Proteins of a virus. A subunit vaccine presents an antigen to the immune system without introducingViral particles, whole or otherwise.

Measles can be prevented by vaccinations. All children should be vaccinated to protect themselves. Given to children beginning with 12 months.

Polio Is caused by a virus that lives in the intestinal tract and sometimes in the throat Was eliminated from the U.S in 1979. Still exists in some developing countries.

Symptoms of Polio: Include:

Fever Fatigue Headache Vomiting Stiffness in the neck pain in the limbs

Up to 95% of all persons infected with polio will have no symptomsThe best way to prevent polio is for all children to be fully vaccinated on time.The inactivated polio vaccine (IPV) protects against polio.

H1N1 Vaccine: ◦ Vaccines to protect against the 2009 H1N1 virus (also called the “swine

flu”) have been produced. Like seasonal flu vaccines, there are two kinds of 2009 H1N1 vaccines: a "flu shot  "; that is given with a needle, usually in the arm; and a nasal spray flu vaccine  . The same manufacturers that produce seasonal flu vaccines also produced the vaccines against the pandemic 2009 H1N1 virus in the same way that the seasonal vaccines are made. Vaccines to protect against 2009 H1N1 are widely available. CDC is now encouraging everyone to get vaccinated against 2009 H1N1, including people 65 years and older.

Did you know?◦ Getting under 5 hours of sleep a night has been shown to

significantly depress the Immune Response. A germ can be considered a virus, bacteria, fungi, protozoan, and

etc. Once a germ invades the body it quickly multiplies, how can you get

rid of them now! We should have a Healthy Immune System, and it fights back by

sending white blood cells to destroy the invaders. While the T-cells surround the invaders, they “eat” them Then, chemically notify the B-cells which produce antibodies that

destroy the germs There are some germs that survive the attack, which can cause

illness. Antibiotics help to finally destroy all the germs and NORMAL health

is restored.