B-cell receptor (BCR) and T-cell receptor (TCR) (BCR and TCR)

The target refers to the coordinated engagement of B-cell receptors (BCRs) and T-cell receptors (TCRs) that facilitates the immune response to conjugate vaccines. In this mechanism, the BCR on a polysaccharide-specific B cell recognizes and binds to the capsular polysaccharide component of the vaccine (1, 5, 8). The entire polysaccharide-protein conjugate is then internalized and processed by the B cell, which acts as an antigen-presenting cell (1, 5). Peptides derived from the carrier protein are subsequently presented on the B cell's surface via Major Histocompatibility Complex (MHC) class II molecules (1, 5, 10). These peptide-MHC complexes are recognized by TCRs on helper T cells, which then provide essential stimulatory signals, such as CD40 ligand and cytokines, to the B cell (5, 7, 8). This 'T-cell help' transforms the typically T-cell-independent polysaccharide response into a T-cell-dependent one, enabling isotype switching to high-affinity IgG antibodies and the development of long-lasting immunological memory (5, 7, 8). This dual-receptor engagement is the fundamental principle behind the efficacy of conjugate vaccines against encapsulated pathogens like Streptococcus pneumoniae and Haemophilus influenzae, particularly in populations with immature immune systems such as infants (3, 7, 8).

Other names

Conjugate vaccine recognition systemBCR-TCR-MHC II interactionGlycoconjugate vaccine targetCognate B-cell-T-cell interactionT-cell-dependent B-cell activation complex

Conjugate vaccines engage B-cell receptors (BCRs) via polysaccharide epitopes; the conjugate is internalized, and carrier-protein-derived peptides are presented on MHC class II to T-cell receptors (TCRs), inducing T-cell help for high-affinity IgG production and memory.