Lecture 14 Notes
Animal Immune System
| I. Two major systems
A. Non-Specific 1. mosltly physical barriers to disease a. skin i. physical barrier ii. is acidic (pH around 3.5) - this kills many bacteria on contact iii. sweat and oils - so same thing - sweat contains an enzyme called lysozyme that kills bacteria - also present in tears and saliva iv. gastric juices - see digestion section v. cilia and mucus - physical barriers 2. If bacteria get in, inflammation occurs a. inflammation triggers additional responses i. blood vessels in area dialate, allowing more blood to flow in ii. this makes the area redder and hotter iii. injured cells in area release hormone histamine - this relaxes vessel walls, allowing more blood flow iv. higher blood temperature can hinder bacterial growth and stimulate repair processes v. if infection becomes widespread, then more responses occur vi. fever - entire body temperature is raised - may be a way to kill off bacteria vii. higher temperatures interfere with iron metabolism in bacteria and then die - so, lowering fevers might allow bacteria to persist viii. body temperature is reset to higher temperature by a hormone called pyrogen (pyro = fire) ix. lymphatic system becomes activated also - this moves microbes and white blood cells around in body x. in lymph nodes (see Figure 24.3A, pg. 486 for diagram), immune system fights and kills invading pathogens B. Specific 1. fights off specific invading organisms, such as viruses and bacteria 2. detects foreign objects in body a. certain molecules that are on the outside of invading pathogens or other foreign objects, that elicit a response from the immune system are called antigens b. immune system in turn produces antibodies, which attach to antigens c. immune system is specific, and has a memory so it can attack pathogens from a previous encounter 3. Humoral system a. this system fights off bacteria in the circulatory system 4. Cell-mediated system a. this system attacks cells that are already infected b. this same system is the one that attackes grafted tissues, resulting in the rejection response in those who get transplants 5. Two major cell types a. B cells i. these produce antibodies ii. antibodies are proteins that attach to antigenic sites iii. humans may contain 100 million to 100 billion different types of antibody producing B cell types - how is this possible with only 50,000 genes? iv. these cells have lots of genetic recombination that allow them to be very diverse v. when an antigen is present, body begins producing lots of different kinds of B cells vi. only those whose antibodies stick to antigen are selected for future reproduction vii. this selective propagation is known as clonal propagation viii. results in a bunch of cells that can fight off the invader ix. some of these cells remain in the lymph system to fight off another invasion later - known as memory cells - can last months to decades x. when the same invader comes back in the future, body produces this B cell type, and can more rapidly fight off infection this time b. T cells i. attack infected cells - some engulf them (phagcytosis) while others inject chemicals (perforins) that cause the invader's cell membrane to break down, killing it ii. there are 3 major types of T cells 1. killer T cells - have chemicals that enter and kill infected cells - they attach to cells with antigen recognizing proteins 2. helper T cells - assist B cells in producing antibodies and attract other B cells to area where pathogens are 3. suppressor T cells - suppress actions of B and T cells after infection is over c. both types produced in bone marrow, from stem cells d. if they mature in bone marrow, they become B cells e. if they mature in the lymph system, they become T cells (see Figure 24.5, pg. 488) 6. Antibody structure and function a. consists of two chains in a "Y" shape b. arms have double chains (see Figure 24.10B, pg 493) c. tips of "Y" portion are the sites where the antibody binds to the antigen d. there are 5 major classes of antibodies in humans i. IgG - attacks bacteria and viruses ii. IgE - responsible for allergic reactions (to pollen grains for example) 7. cells that have antibodies attached to them attract phagocytes and are engulfed and destroyed C. Self Recognition 1. Why doesn't our immune system destroy our own cells? 2. Cells have various molecules on them that comprise the Major Histocompatability Comlex (MHC) - cells that have these proteins and other molecules are recognized as "self", not foreign 3. Blood Groups a. 4 major kinds: A, B, O, and AB b. each blood type has red blood cells with different antigens c. important when doing blood transfusions d. A can receive blood from a person with A blood, but not B blood e. same for someone with B blood f. people with AB blood can accept blood from either A or B - they are universal acceptors g. O type people have none of the A or B antigens, and can NOT receive blood from either group, only from O people h. However, O type people can donate to anyone, since their blood lacks the antigens of either A or B type people - they are universal donors i. if wrong blood is transfused, can cause clotting and death 4. Auto-immune disease a. something goes wrong and immune system does not see MHC - instead, attacks own body cells b. rheumatoid arthritis may be one example of this c. allergies - overreactions to normal antigens, such as grass pollen here, IgE antibodies bind to mast cells, resulting in massive releases of histamines, producing swelling and irritation, vessel dialation too d. sometimes if vessel dialation is too rapid, blood pressure drops to quickly, and too lowly, resulting in death. Known as anaphylactic shock - this is the bee sting response if you're allergic to bees Best treatment is to give a counter to the histamines, such as norepinephrine e. AIDS - virus attacks helper T cells, comprimises immune system i. people die more from associated diseases than AIDS itself ii. AIDS caused by virus known as HIV (human immunodeficiency virus) |