Mycoplasmas as Immunomodulators

Abstract

Following successful adherence and colonization of host tissues by invading mycoplasmas, interactions between organisms and their host immune system are initiated. Specific, protective antimycoplasmal humoral and cellular immune responses are often only partially effective, thus leading to a chronic persistent infection. In addition, mycoplasmas can induce nonspecific modulation of host immune responses thereby contributing to the immuno-pathological manifestations of mycoplasmal infections. Nonspecific suppression of host immune responses may affect the host’s capacity to eradicate the evading mycoplasma and it also may render the host more susceptible to infections with other microorganisms. On the other hand, nonspecific-mitogenic activation of host immune mechanisms may be responsible for the massive cellular responses, lymphoid hyperplasia, cell infiltration, inflammation and chemotactic phenomena which often characterize mycoplasma infections. It is obvious that the immune mechanisms operating during any mycoplasma infection are complex and depend on both the mycoplasma species and the infected host. It is therefore crucial to clarify in each case the nature of specific as well as nonspecific interactions between the invading mycoplasma and its host immune cells. This paper will address the capacity of mycoplasmas to modulate immune responses either by suppression or by nonspecific activation.