B cell receptor and antibody recognizing Streptococcus pneumoniae serotype 3 capsular polysaccharide

B cell receptors (BCRs) and antibodies that recognize Streptococcus pneumoniae serotype 3 capsular polysaccharide are adaptive immune molecules that specifically bind the unique disaccharide repeating structure (alternating glucose and glucuronic acid) of the serotype 3 capsule. Upon exposure to this antigen, such as during infection or vaccination, B cells with surface receptors specific to this epitope undergo activation, leading to production of antibodies—predominantly IgG in the context of T cell help and conjugate vaccines. These antibodies mediate serotype-specific immune protection primarily via opsonophagocytosis. However, the serotype 3 polysaccharide has been shown to be less immunogenic and evokes lower protection with existing vaccines, partly due to structural properties of the capsule and immune evasion strategies of the bacterium. Measurement of these antibodies is used to monitor immune status and response to pneumococcal vaccination, though immune correlates of protection are less clear for this serotype than for others.

Other names

Pneumococcal serotype 3 polysaccharide-specific B cell receptorAnti-pneumococcal serotype 3 antibodyPn3P-specific antibodyAnti-serotype 3 CPS BCR/antibodyAntibodies to Streptococcus pneumoniae type 3 capsule

Recognition of the type 3 capsular polysaccharide antigen by surface immunoglobulin on B cells leads to clonal expansion and antibody production. Antibodies opsonize the bacteria, marking them for phagocytosis and complement-mediated killing. Induction of serotype-specific IgG with help from T cell-dependent and -independent immune pathways.