The Benefits, or Otherwise, of the Immune Response
Probably the most recognised feature of the immune response which causes problems is that of immunodeficiency, and the prime example of this is HIV/AIDS. The HIV virus enters the CD4+ cell, loses it's coat, and a single stranded DNA copy of the viral RNA is made by the viral enzyme HIV reverse transcriptase. A complementary DNA strand is then produced giving a replication of the virus and incorporates into the host genome. When an infected T cell is activated, infectious viral particles are produced which overcome the hosts defence mechanisms and progressively infect more T cells which die off and decrease in numbers. Polyclonal B cell activation also occurs causing a large increase in IgG. Because of the immune systems natural response to infection the virus is spread throughout the system. Eventually, after massive losses of CD4+ cells, the HIV virus turns into AIDS.
Tumour cells have a number of surface structures which the immune system can recognise as antigenic. …
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