Solutions to Review Problems

1. C
   Histamine triggers the inflammatory response and dilates blood vessels, thereby increasing blood flow to an injured area, which increases the number of immune cells that can reach the damaged tissue. In contrast, cytokines trigger the fever response and activate B lymphocytes, which in turn produce immunoglobulin.
2. Neutrophils are the first responders to inflammation and phagocytize pathogens. Eosinophils and basophils are involved in inflammation and the allergic response, and both are involved in combating parasites. Among other actions, basophils specifically stimulate histamine release, while eosinophils release cytokines. Macrophages phagocytize pathogens and dead or damaged cells. Dendritic cells present antigens to allow for a targeted immune response.
3. B
   The major histocompatibility complex (MHC) presents proteins to immune cells. MHC II in particular presents to helper T lymphocytes, and these cells then activate other T cells and B cells. Cytotoxic T cells recognize and attack foreign antigens, natural killer cells similarly destroy tumor cells and cells infected with viruses, and plasma cells release large quantities of antibodies, but none of these types of cells interact with MHC.
4. D
   Macrophages are part of the general immune response and do not exert a targeted effect or retain memory of antigens. Cytokines activate B cells but do not themselves possess a memory for antigens. Neutrophils are phagocytic and also do not have a memory for specific antigens.
5. Both T lymphocytes and B lymphocytes begin development in the bone marrow. Immature T cells are released into the bloodstream, where they travel to the thymus. It is in the thymus that T cells complete the maturation process and develop their permanent characteristics. B cells, however, complete their maturation in the bone marrow. When B cells are released from the bone they are mature and ready to undertake their anti-pathogenic activities.
6. Active immunity is due to exposure to an antigen, for example during infection or vaccination. Passive immunity requires the transfer of antibodies from one individual to another. This can occur, for example, from a pregnant woman to her fetus.
7. C
   The heavy chain, light chain, and cytoplasmic tail are all components of antibody structure, but none of them play a role in binding antigens. It is only the N terminus that binds to antigens and thus determines the specificity of the antibody.