Chpt 43 Immune System

I. Lines of Defense

• A. 1st line of defense– 1. non-specific – not targeting any particular

antigen

• The invader,

• The villain

• The bad guy

• ….according to your body

Virus, bacteria, pollen, Non-Self cells

• a. skin – oily, dead barrier, acidic sweat (pH 3-5)

• b. mucous membranes- traps invaders

• c. antimicrobial proteins- ex: lysozyme in tears etc… breaks down bacterial cell walls

• d. cilia – brush pathogens out of body

• e. gastric juice – HCl

• f. symbiotic bacteria

B. 2nd line of defense

• 1. Phagocytes – “cell eaters”- wbc’s that engulf pathogens– a. neutrophils- 60-70% WBCs; engulf and destroy

microbes at infected tissue – b. monocytes- 5% WBCs; develop into….

– c. macrophages- enzymatically destroy microbes

– d. eosinophils- 1.5% WBCs; destroy large parasitic invaders (blood flukes)

– e. natural killer (NK) cells-destroy virus-infected body cells & abnormal cells

Types of phagocytes• Neutrophils

60-70% WBCs; engulf and destroy microbes at infected tissue

• Monocytes

5% WBCs; develop into….

• Macrophages

enzymatically destroy microbes

• Eosinophils

1.5% WBCs; destroy large parasitic invaders (blood flukes)

• Natural killer (NK) cellsdestroy virus-infected body cells & abnormal cells

• 2. Complement- group of proteins that “complement’ the immune response– a. help attract phagocytes– b. help destroy foreign cells by causing cell lysis

• 3. Interferons – chems secreted by

virus-infected cells that cause nearby cells to take action to protect themselves (an alarm)

4. Inflammatory Response – nonspecific response

• a. Tissue injury causes release of histamine by basophils (wbc’s in connective tissue)

• b. Vasodilation (dilation of blood vessels) caused by histamine – increases blood flow & allows wbc’s to move easier– increases redness, temp & swelling (inhospitable envr for

pathogens)

• c. phagocytes --attracted to injured area by complement – eat pathogens & damaged cells

• d. complement helps phagocytes, stimulates basophils & helps lyse foreign cells

The Inflammatory Response

C. 3rd line of defense – Immune Response– target specific

• 1. Targets specific antigens– a. Antigen: a foreign molecule that causes a response by

wbc’s (virus, bacteria, fungus, protozoa, parasitic worms)

– b. Antibodies: antigen-binding immunoglobulin, produced by B cells

– c. Antigen receptors: plasma membrane receptors on B and T cells

– d. Lymphocyctes (wbc’s)

1) pluripotent stem cells... they can become anything

• B Cells (bone marrow)

• T Cells (thymus)

2. Self or Foreign Antigen?

• a. Major Histocompatibility Complex --- MHC– 1) MHC is a group of cell-surface proteins unique to

each individual– 2) Every cell in an individual’s body has these same

proteins– 3) This is how the immune system knows which cells

are “self” & which are “foreign”– 4) Coded for by 20+ genes--- millions of dif combo’s

3. B cells• a. lymphocytes created & matured in bone

marrow

• b. cell membrane has antigen receptor proteins called antibodies

• c. antibodies (aka immunoglobulins)– 1) proteins – 2) antigen specific– 3) 5 classes – IgA, IgD, IgE, IgG, IgM – each has

their own activity or “style” of working

• 4) structure– a) y-shaped protein w/ a constant region & a variable

region– b) constant regions determine the class of antibody– b) the variable region is what allows them to recognize

the individual antigens

• 5) function– a) binds to antigen so the antigen can’t bind to cell

(inactivates antigen)– b) binding to antigen “tags” it to be eaten by a

phagocyte– c) binding to antigen stimulates complement proteins to

begin lysis of cell

• 6) proliferation– a) when b cells come across their particular antigen

it causes reproduction & 2 types of daughter cells are produced

• 1) plasma cells – B cells that release antibodies into blood

• 2) memory cells – long-lived B cells that don’t release their antibodies until a subsequent/later infection by the particular antigen

• 3) so you’ll be immune the next time that antigen gets into your cells

4. T cells

• a. originate in bone marrow but mature in thymus• b. they have antigen receptors on the cell membrane

but don’t produce antibodies• c. T cells bind themselves to cells that display non-

self markers with the MHC (major histocompatibility complex)– 1) cells infected by viruses

– 2) cancer cells have aberrant MHC’s

– 3) transplanted cells

• d. when T cells encounter non-self cells they divide & form 2 types of cells– 1) Killer T cells (cytotoxic cells) ---recognize &

destroy non-self cells ---puncture– 2) Helper T cells – stimulate creation of B cells &

Killer T cells

*primary response – gradual rise & fall*secondary response – more rapid, more intense response &

antibody levels remain high for a much longer time

5. Clonal Selection

• a. when a B or T cell binds to its specific invader it starts producing clones of itself

• b. the only cells “selected” to be cloned are the ones responding to that particular antigen

6. Cell-mediated Response• a. mostly T cells• b. T cell binds to non-self/infected cell• c. T cells produce killer T cells• d. Helper T cells stimulate production of B &

killer T cells– 1) when they bind to wbc’s they release interlukins

(chemicals that communicate “between leukocytes”)– 2) interlukins cause proliferation of wbc’s through

positive feedback

7. Humoral Antibody Response

• a. mostly B cells – antibodies put in to blood

• b. B cells produce plasma cells

• c. B cells produce memory cells

• d. B cell production is stimulated

Types of immune responses

8. Active Immunity• a. causes the body to

actively produce antibodies

• b. acquired during infection or through a vaccination– 1) vaccine - inactive or

fragment of antigen injected into body to cause an immune response so that memory cells are formed ---so body creates immunity without getting sick

9. Passive immunity

• a. the body does not create antibodies

• b. the body does not create immunity to the pathogen

• c. mother’s antibodies are transmitted to baby via placenta or milk

• d. antibodies are donated via blood

Abnormal immune function• Allergies (anaphylactic shock): hypersensitive responses to environmental antigens

(allergens); causes dilation and blood vessel permeability (antihistamines); epinephrine

• Autoimmune disease: multiple sclerosis, lupus, rheumatoid arthritis, insulin-dependent diabetes mellitus

• Immunodeficiency disease: SCIDS (bubble-boy); A.I.D.S.