B-cell receptor recognizing Streptococcus pneumoniae type 5 capsular polysaccharide epitopes

The B-cell receptor (BCR) recognizing Streptococcus pneumoniae type 5 capsular polysaccharide epitopes is a membrane-bound immunoglobulin complex that serves as the primary sensor for the serotype 5 pneumococcus on B lymphocytes. It specifically recognizes the repeating epitopes of the type 5 capsular polysaccharide (CPS5), which is a major virulence factor and a key component of pneumococcal vaccines. The BCR consists of an antigen-binding membrane immunoglobulin and the signaling subunits CD79A and CD79B. Binding of the multivalent CPS5 antigen to the BCR induces receptor cross-linking and activates intracellular signaling cascades, notably the Bruton's tyrosine kinase (Btk) pathway, which is essential for the T-cell independent response to polysaccharide antigens. This activation leads to the production of serotype-specific antibodies that opsonize the bacteria for clearance by the immune system. This BCR is the functional target of both polysaccharide and conjugate vaccines, and its signaling can be inhibited by Btk-targeting drugs, which may increase susceptibility to pneumococcal infections.

Other names

Anti-Sp5 B-cell receptorSerotype 5-specific B-cell receptorPneumococcal serotype 5 BCRAnti-CPS5 BCRAnti-Pn5 BCR

Vaccines containing the type 5 capsular polysaccharide act as agonists by binding to and cross-linking the BCR, which initiates the B-cell receptor signaling pathway (involving Btk, Syk, and Lyn) to drive B-cell activation and the production of protective antibodies. Btk inhibitors act as antagonists of this signaling pathway by blocking the activity of Bruton's tyrosine kinase, thereby preventing the B-cell response to the pneumococcal antigen.