Immune system immunological memory

The ideal of any vaccine is to provide life-long protection to the individual against disease. Immunological memory (Chapter 14) depends upon the survival of cloned populations of small B and T lymphocytes (memory cells). These small lymphocytes have a lifespan in the body of ca. 15-20 years. Thus, if the immune system is not boosted, either by natural exposure to the organism or by re-immunization, then immunity gained in childhood will be attenuated or lost completely by the age of 30. Those vaccines which provide only poor protection against disease have proportionately reduced time-spans of effectiveness. Yellow fever vaccination, which is highly effective, must therefore be repeated at 10-year intervals, whilst typhoid vaccines are only effective for 1-3 years. Whether or not immunization in childhood is boosted at adolescence or in adult life depends on the relative risks associated with the infection as a function of age. 

Studies have consistently identified the immune system as a target for JP-8. Due to variability in routes of exposure and chemical composition, it is likely that there are a number of pathways contributing to the development of immunotoxicity, including the generation of free radicals, release of platelet-activating factor, interference with immunological memory, or the alteration of neuropeptides and cytokines. With further... 

One of the most important features of the immune system is that, once an animal has encountered a particular pathogen, the system confers protection against future infection. This immunological memory means that if the same pathogen or antigen is encountered a second time, perhaps even decades after... 

Immune defense depends on four complex, interactive systems cell-mediated immunity (T lymphocytes) humoral antibodies (immunoglobulins) the phagocytic system and the complement system. The last two systems are nonspecific in that they have no immunological memory for the antigen. Only the second and fourth systems are composed of plasma proteins. Immunodeficiency states characterized by recurrent infections may be the result of a defect in any one of these systems or combinations thereof. 

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