Immune response genetic differences

Live vaccines are normally weakened strains that do not cause diseases in the host, but stiU can stimulate the immune response. A typical example is the poho vaccine. The weakening of microorganisms or attenuation of the vims or bacteria can be accompHshed by passage through different substrates and/or at different temperatures. Modem genetic engineering techniques can also be used to attenuate a vims or bacterium. 

For effective sensitization, a chemical must therefore be inherently protein-reactive or must be converted in the skin to a protein-reactive metabolite. Chemicals that are unable to associate effectively with proteins will fail to stimulate a cutaneous immune response. For those chemical contact allergens that require metabolism to a protein reactive species, it is possible that genetic differences in metabolism may play a role in the differential susceptibility of individuals to the development of contact hypersensitivity responses to these materials. 

It may have different outcomes ranging from genetic damage to immune responses. This is true of all interactions between chemicals and macromolecules, as will be seen later in this chapter and in chapter 7. 

Although the cellular and humoral response in experimental animals tends to be relatively uniform, it must be remembered that in man (and domestic animals) the immune responses can vary enormously. This is undoubtedly related to human genetic diversity - unlike the uniform genetic background of most experimental animals. These responses have been much studied in hydatid disease and (T. solium) cysticercosis. In the latter case, the frequency of different precipitation bands in serum immuno-electrophoresis (Fig. 11.8) and of the immunoglobulin classes (Table 11.4) show great variation between patients (226). Moreover, some patients show no humoral or cellular response whatsoever (226). Similarly, there is much variation in the immune responses to hydatid disease and, again, some patients show no detectable antibody (734). 

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