B-cell receptor (BCR) on pneumococcal serotype 9N-specific B cells (BCR)

The B-cell receptor (BCR) on pneumococcal serotype 9N-specific B cells is a membrane-bound immunoglobulin complex that serves as the primary sensor for the capsular polysaccharide of Streptococcus pneumoniae serotype 9N. Serotype 9N is a clinically significant pathogen responsible for invasive pneumococcal diseases, including pneumonia, bacteremia, and meningitis, particularly in adult populations (CDC, 2024; Merck, 2024). The BCR consists of a surface-bound antibody non-covalently associated with the CD79A and CD79B signaling subunits (Kurosaki et al., 2010). Upon binding the specific 9N polysaccharide antigen, the BCR initiates a signaling cascade that drives the B cell to proliferate and differentiate into plasma cells that secrete high-affinity antibodies (Kamerling et al., 1975). These antibodies are essential for opsonizing the bacteria, facilitating their destruction by the host's immune system. This specific BCR population is the primary target of vaccines such as the 23-valent polysaccharide vaccine (PPSV23) and the newer 21-valent conjugate vaccine (V116), which are designed to elicit protective immunity against serotype 9N (CDC, 2024; Platt et al., 2023). Understanding the specific BCR repertoire for serotype 9N helps in evaluating vaccine immunogenicity and the development of therapeutic monoclonal antibodies.

Other names

Surface immunoglobulinsIgAntigen receptor of B-lymphocytesPneumococcal serotype 9N-specific B-cell receptorBCR-9N

The target functions by binding specific antigens—in this case, the capsular polysaccharide of Streptococcus pneumoniae serotype 9N—which induces receptor clustering and activates intracellular signaling pathways involving Lyn, Syk, and PLC-gamma2. This activation leads to B-cell proliferation, isotype switching, and the generation of memory B cells and plasma cells that produce serotype-specific antibodies.