Staying Put

A large number of B cells inhabit the marginal zones (MZ) of the spleen, where they maintain steady contact with recirculating antigens in the blood. These lymphocytes respond rapidly to bacteria by mobilizing and differentiating into extensive clusters of antibody-producing plasma cells. Lu et al. show that two integrins involved in lymphocyte trafficking across endothelium, LFA-1 and α4β1, appear to be responsible for the migration and localization of MZ B cells. Large-scale egress of B cells from the MZ occurred when interactions of these integrins with their respective ligands were blocked. The retention of lymphocytes within lymphoid niches suggests a wider role for some integrins associated with lymphocyte trafficking. T. T. Lu, J. G. Cyster, Integrin-mediated long-term B cell retention in the splenic marginal zone, Science 297, 409-412 (2002). [Abstract] [Full Text]