Dynamic Defense System

Chapter 43 :)

I. Nonspecific Defenses Against Infection

A. First line of defense 1. Intact skin – barrier that can’t normally be

penetrated by microbes2. Mucous membranes – line digestive, respiratory

and urogenital tracta. Mucus – fluid secreted by mucous membranes –

traps microbes and is removed from body by cilia (tiny hairs)

b. Acid – produced in stomach destroys microbes before they go into the digestive tract

B. Second line of defense (used if a microbe makes it past

the first line)

1. Phagocytic white blood cells

a. Neutrophils – attracted by chemicals released when a cell is damaged enter infected tissue surround and destroy microbes using

phagocytosis live only a few days

B. Second line of defense (used if a microbe makes it past

the first line)

b. Monocytes enter into damaged tissue and form

macrophages attach to microbe’s surface, “eat” it and destroy it

using lysosomes – YUM!! macrophages live permanently in lungs, liver,

kidney, brain, lymph nodes and spleen

B. Second line of defense (used if a microbe makes it past

the first line)

c. Eosinophils defend against large parasites (eeww)

B. Second line of defense (used if a microbe makes it past

the first line)

2. Natural Killer (NK) cells destroy virus infected body cells (not microbes

but the cells they have invaded) cause cell membrane to burst

B. Second line of defense (used if a microbe makes it past

the first line)

3. Inflammatory Response response to tissue damage (from injury) or

to entry of microorganisms arterioles dilate (open) and venules

constrict (shrink) so that the blood supply increases in the area (swelling and redness)

aid in blood clotting and repair block spread of microbes

B. Second line of defense (used if a microbe makes it past

the first line)

a. Chemical signals cause the inflammation

i. Signal from invading organism

ii. Histamine

released by body cells when tissue is damaged

produced by basophils and mast cells

B. Second line of defense (used if a microbe makes it past

the first line)

4. Antimicrobial Proteins

a. Lysozyme enzyme present in tears, saliva and

mucus destroys microbes

B. Second line of defense (used if a microbe makes it past

the first line)

b. Complement system 20 proteins that carry out cascade of

steps Cause microbes to burst

B. Second line of defense (used if a microbe makes it past

the first line)

c. Interferons secreted by virus infected cells don’t help the infected cell, but diffuse

into neighboring cells neighboring cells produce chemicals to

slow down viral reproduction limit cell to cell spread of viruses

II. Specific Line of Defense – IMMUNE SYSTEM

Specific response to an invader (not general defense like first/second line)

II. Specific Line of Defense – IMMUNE SYSTEM

A. Lymphocytes

1. 2 Types – B lymphocytes (B cells) and T lymphocytes (T cells)

2. Circulate through blood and lymph and are concentrated in lymph nodes and spleen

3. Display specificity – recognize and respond to a specific foreign invader

II. Specific Line of Defense – IMMUNE SYSTEM

4. Antigen – foreign molecule that causes a response by lymphocyte-can be found on viruses, bacteria, fungi, protozoa,

parasitic worms

-also found on pollen (allergies) and transplanted tissue (like heart transplant)

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are needed to see this picture.ANTIGEN:Enemy Invader

II. Specific Line of Defense – IMMUNE SYSTEM

5. B Cells (form and mature in Bone marrow) Produce antibodies that are specific to a particular

antigen 5 classes of antibodies (IgA, IgD, IgE, IgG, IgM) Structure of antibodies is basically the same except

for a variable region that makes the antibody recognize specific antigens

Antibody binds to antigen and inactivates it Macrophage comes and eats it

II. Specific Line of Defense – IMMUNE SYSTEM

B. Primary Immune Response- takes 10-17 days (when you get sick)

1. Invader attacks a body cell

2. Antigens from invader bind to a B cell with the correct receptor

3. B cell proliferates (makes lots of copies of itself) and makes two types of cells

II. Specific Line of Defense – IMMUNE SYSTEM

4. Plasma cells – short lived – secrete antibodies that clear the invader from the body (takes about 10-17 days)

5. Memory cells – long living cells that recognize the same antigen and respond rapidly to a NEW infection

II. Specific Line of Defense – IMMUNE SYSTEM

C. Secondary Immune Response – takes 2-7 days (usually don’t get sick)

1. Individual is attacked by same invader at a later time

2. Memory cells recognize the antigen much faster and produce a stronger response (2-7 days)

II. Specific Line of Defense – IMMUNE SYSTEM

D. MHC – major histocompatibility complex

1. Helps immune system tell the difference between self (you) and nonself (invader)

2. Group of glycoproteins (remember those from membrane structure)

3. MHC is unique to all individuals (except identical twins or clones )

II. Specific Line of Defense – IMMUNE SYSTEM

4. T Cells (form in bone marrow and mature in Thymus gland) Have receptors for antigens Recognize nonself molecules If nonself cell is identified, T cells divide rapidly

and produce Cytotoxic T cells (killer T cells) that puncture

infected cells and make them burst Helper T cells – stimulate more B cells and killer

T cells to form to help fight the invader faster

II. Specific Line of Defense – IMMUNE SYSTEM

E. Categories of Immune Responses

1. Cell-mediated response uses mostly T cells and responds to any

nonself cell triggering the following events:

E. Categories of Immune Responses

T cells produce killer T cells to destroy infected cells

T cells produce helper T cells Helper T cells bind to macrophage Helper T cells release interleukins that

stimulate division to make more T cells and activates B cells

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E. Categories of Immune Responses

2. Humoral Response Responds to antigens or pathogens

circulating in the blood or lymph fluid B cells produce plasma cells Plasma cells release antibodies that bind to

invading antigen B cells produce memory cells for future immunity

F. Problems in Immune System

1. Blood Transfusion – individual has specific antigens on their blood cells (i.e. Type A blood has A antigens) Person with Type A blood will make

antibodies to type B If you try to give type B blood to a Type A

person, their body will mount an immune response and reject the blood

F. Problems in Immune System

2. Organ/Tissue Transplant MHC recognizes self from non-self Organs from a different person are viewed by the

body as non-self and will be rejected by the person receiving the organs

Doctors must try to match the MHC of donor and recipient as closely as they can

Medicine must be taken for the rest of the recipients life to prevent rejection

Be an Organ Donor – you might be the MHC match and

Save a LIFE!!!

F. Problems in Immune System

3. Autoimmune Diseases immune system turns against it’s

own cells (doesn’t recognize self anymore)

F. Problems in Immune System

4. Immunodeficiency Disorders (like AIDS or SCID) Immune system is suppressed and

doesn’t function properly Simple viruses/bacteria can’t be killed by

immune system and person can die from common illness

F. Problems in Immune System

In allergies such as hay fever, an allergen, such as pollen, triggers histamine release from mast cells, inducing vascular changes and typical symptoms.

Pollen

III. Human Help

A. Antibiotics – chemicals used to defend against bacteria or fungi – generally work by making holes in cell wall causing bacteria to burst

B. Vaccines – inactivated viruses or fragments of virus, bacteria or other microbes Stimulate formation of memory cells

without person getting the disease If individual is exposed to disease,

immune response is quick – usually resulting in no symptoms of infection

C. Passive Immunity – transfer of antibodies from an individual that had a disease to one who is newly infected Newborn babies protected by antibodies

of mom from placenta or breast milk