27
1. The first and second lines of defense are nonspecific, meaning the response occurs regardless of the antigen. Conversely, the third line of defense is specific for the particular invading antigen.
2. 1-E, 2-C, 3-H, 4-G, 5-D, 6-A, 7-B, 8-F
3. The cell-mediated response targets intracellular pathogens such as viruses and relies on T cells.
4. Once the particular lymphocyte (either B or T cell) is selected for by a particular antigen, it will produce two populations of cloned cells: the active cells that take care of the immediate infection, and a second population of memory cells that last for years (even decades) awaiting a second invasion. If the same antigen presents itself again, the memory cells respond immediately to remove the invader before it has a chance to cause problems. Vaccines work in the same way, except the initial “infection” is only a part of the virus/bacterium, just enough to stimulate a lymphocyte response (but not itself able to cause the disease).
5. The other barriers of your body provide the first line of defense. This includes skin, sweat, saliva, and tears.
6. The humoral response targets extracellular pathogens and relies on B cells to produce antibodies to bind to and help remove the invader.
7. Passive immunity is when antibodies are given to the patient (and are not produced by the patient’s own B cells, as they are in active immunity). Passive immunity is an important treatment option when the patient does not have the luxury of time to produce their own antibodies (venom from a snake bite, or babies receiving antibodies from their mother).
8. The flu virus mutates every year, and the previous year’s vaccine will no longer be close enough of a “match.”
9. a. When a snake-bite victim receives antivenin, they are given a population of antibodies specific for that particular venom protein. Because the antibodies were generated by a different source (and not the bite-victim themselves), this is an example of passive immunity.