Answer to Question 1
Changes in the immune system have important implications as people age. Older adults become more prone to serious consequences of illnesses, such as those caused by viruses, that are easily defeated by younger individuals. Older adults do not seem to benefit as much as younger people from immunizations. Also, the rates of various forms of leukemia, as well as other cancers, increase with age. In addition, the immune system may begin attacking the body in a process called autoimmunity.
Autoimmunity results from an imbalance of B- and T-lymphocytes, giving rise to autoantibodies. Autoimmunity causes several disorders, including rheumatoid arthritis.
Answer to Question 2
There are three major types of cells in the immune system that form a network of interacting parts: cell-mediated immunity (consisting of cells originating in the thymus gland, or T-lymphocytes); immunity based on the release of antibodies in the blood, such as those acquired from immunization or manufactured in bone marrow (B- lymphocytes); and nonspecific immunity (monocytes and polymorphonuclear neutrophil leukocytes).
Representative vertebrate circulatory systems.
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The humoral and cellular immune response. At the left is the humoral (or B-cell mediated); at the ...
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