Immune System Notes
- Non-specific (p. 174 N)
- skin and other first line defenses (p. 852 C)
- physical barrier
- cells shed so microbes can't colonize
- oil and sweat have pH 3-5 to discourage microbes
- saliva - lysozyme to digest bacterial cell wall
- tears - lysozyme
- mucous (yummy) - to trap microbes and airborne pathogens (especially in
respiratory tract)
- stomach - low pH
- White Blood Cells (WBC)
- engulf invaders - phagocytes (p. 853 C)
- glycoproteins as cell labels
- macrophages (p. 854 C)
- Antimicrobial proteins (p. 854 C)
- complement (so-called because complements other arms of immune
system)
- about 20 different proteins in inactive form
- make membrane attack complex
- attract macrophages
- interferons
- secreted by cells infected by virus
- cause neighboring cells to produce protein which interfere with
viral replication
- Inflammatory Response (p. 855 C)
- Local injury or infection
- vasodilation near injury or infection increases blood causing redness
and heat
- dilated blood vessels more permeable to fluids - edema
- increased blood flow brings more WBC
- some WBC release histamine when injured
- histamine causes local vasodilation
- more widespread infection
- some WBC release pyrogens which set the body thermostat higher -
fever
- inhibits bacterial growth
- speeds phagocytosis and repair
- Specific - depends on two classes of lymphocytes, both produced in the bone marrow;
cells mature in bone marrow and T cells mature in thymus
- Humoral - depends on B cells (p. 176 N, p. 858 C)
- each cell is specific for one antigen (ag)
- when meet the ag, become activated and divide to form many clones
- the clones produce antibodies (ab) for 4-5 days before dying
- Cell - mediated (depends on T cells) (p. 178 N, p. 867 C)
- T cells don't recognize free ag
- when macrophage devours microbe, displays ag on membrane
- Helper T (TH) cells recognize ag on macrophage, becomes activated and
divides rapidly producing clones
- clones secrete interleukin which activates (or helps) other T and B cells
- Killer T (cytotoxic T or TC) cells are also activated
- TC recognize your own cells that are displaying ag or unusual markers
(e.g., cancer, organ transplants) and destroy them
- any viruses released by this process dealt with by humoral immunity
- Suppressor T (TS) cells turn off immune response but not well understood
- Memory T cells are long-lived and respond faster to second exposure
- Immune Disorders
- Allergies
- over-reaction to a harmless substance
- response is caused by histamine
- tissue swelling
- excess mucous (yum)
- constricted airway
- sneezing
- tears
- Lupus - immune response to your own cells parts (especially nucleic acids)
- rheumatoid arthritis - immune response to joint cartilage
- insulin-dependant diabetes - attack the insulin producing cells of pancreas
- multiple sclerosis - attack myelin sheath
- AIDS
- HIV attacks TH cells
- some cells are killed by immune system but others produce more virus
- immune system slowly loses
- Vaccines
- inactivated bacteria or virus or some other ag
- provokes immune response but not the disease or illness
- memory cells react faster to second exposure
- some pathogens mutate too quickly to be eliminated by vaccines