Immunological aspects of infections part 23

Capsules play an important role for long-term survival of pathogens. For example, group A streptococci have a hyaluronic acid capsule that is identical to hyaluronic acid in humans. While antibodies can be obtained following immunization with the streptococcal hyaluronic acid, they are nonprecipitating antibodies and are not effective in eliminating the organisms. Polysaccharide antigens of both the pneumococcus and the meningococcus capsules can inhibit phagocytosis of the organism and mucoid secretions of these polysaccharides can block the activation of the alternate pathway of complement.