Antigenic components used in vaccines and their possible role in protection

The success of active immunization depends on the production of antibodies or immunologically active cells directed against antigens of the parasite, which are involved in pathogenesis. These could be substances mediating attachment, antiphagocytic materials, structures involved in motility, or toxins and toxic enzymes. An additional target mechanism in mycoplasmas could be the exposed membrane and its metabolic mechanisms. The results of these immune reactions appear as inhibition of attachment, as opsonization, immobilization, antitotic effects or metabolic inhibition. Often only an infection with attenuated organisms will provide sufficient protection, suggesting the necessity of more intensive immunologic stimulation or an involvement of antigens that are present only in small quantities. To minimize side effects, the optimal vaccine should contain only antigens that are known to be relevant for protection.