Chpt 43 Immune System

I. Lines of Defense A. 1 st 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. 2 nd line of defense 1. Phagocytes – “cell eaters”- wbc’s that engulf pathogens –a. neutrophils % 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) cells destroy 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. 3 rd 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.