New views of BCR structure and organization

Recent work has provided new insights into the stoichiometry of BCR subunit s, as well as the organization of the BCR before and after engagement by an tigen. On resting cells, the BCR may be pre-assembled into oligomeric recep tor complexes that generate a basal level of signaling. After antigen bindi ng, the aca may be organized into larger receptor arrays that reside in lip id rafts - sites where signaling enzymes are concentrated. The critical rol e of BCR, assembly and organization in B cell function is underscored by th e recent findings that this process is altered in many B cell tumors.