Chpt 43 Immune System. I. Lines of Defense A. 1 st line of defense –1. non-specific – not...
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Transcript of Chpt 43 Immune System. I. Lines of Defense A. 1 st line of defense –1. non-specific – not...
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
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
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.