BCA-1 may play a dual role, promoting both B-cell homing during normal conditions and the pathologic accumulation of B cells in Helicobacter-induced disease. The present studies also provide some of the first information correlating bacteria and/or bacterially derived products with the local expression of a specific chemokine and with ensuing B-cell accumulation.

This study is a sequel to early investigations that indicated that the receptor for BCA-1 (CXCR5) is highly expressed on circulating blood B lymphocytes and on Burkitt’s lymphoma cells, and that mice deficient in this receptor do not have normal follicle and germinal center formation in the spleen and Peyer’s patches (15–17). Thus, the precedent for BCA-1/CXCR5 expression and the elicitation of B cells had been established, but the potential contribution of this ligand/receptor pair in the pathology of specific diseases had not been well explored. It should be underscored that the biology of B-cell homing and chemotaxis is not well understood and that all of the above studies have provided significant insight toward defining this biological phenomenon. As manuscripts relating to the structure, function, and in vitro cell biology of chemokines fill volumes of scientific journals, investigations like those by Mazzucchelli et al. begin to address the physiological relevance of chemokines. Taking a broad view of the field, chemokine researchers have developed