Antigen receptors on B lymphocytes.

Recent studies on the structure of the B cell antigen receptor demonstrate that the membrane-bound and antigen-binding immunoglobulin molecules are noncovalently associated with a heterodimer of two novel transmembrane proteins. The B cell antigen receptor is thus a multicomponent receptor complex whose structural features are similar to those of the T cell antigen receptor complex. Cross-linking of the B cell antigen receptor results in rapid tyrosine phosphorylation of substrate proteins. This suggests that the B cell receptor belongs to a subgroup of the tyrosine kinase receptor family with a noncovalently associated src-like tyrosine kinase.