B cell receptors perform which primary function?

B cell receptors perform which primary function?

• A. Phagocytose pathogens
• B. Bind soluble antigen and initiate B cell activation
• C. Produce antibodies directly
• D. Kill infected cells

Answer: (B)

B cell receptors are membrane-bound immunoglobulins whose main role is to recognize and bind antigen, then trigger B cell activation. When the BCR binds a specific antigen, signaling through its associated Igα/Igβ chains starts a cascade that causes the B cell to proliferate and differentiate. This initial activation not only sets off clonal expansion but also promotes internalization of the antigen for processing and presentation to helper T cells, which provides further signals for class switching and affinity maturation. The antibodies that ultimately combat the pathogen are produced later by plasma cells derived from these activated B cells, not by the BCR itself. Phagocytosis is carried out primarily by other immune cells, and killing of infected cells is the job of cytotoxic T cells.

B cell receptors are membrane-bound immunoglobulins whose main role is to recognize and bind antigen, then trigger B cell activation. When the BCR binds a specific antigen, signaling through its associated Igα/Igβ chains starts a cascade that causes the B cell to proliferate and differentiate. This initial activation not only sets off clonal expansion but also promotes internalization of the antigen for processing and presentation to helper T cells, which provides further signals for class switching and affinity maturation. The antibodies that ultimately combat the pathogen are produced later by plasma cells derived from these activated B cells, not by the BCR itself. Phagocytosis is carried out primarily by other immune cells, and killing of infected cells is the job of cytotoxic T cells.