BCA-1 is highly expressed in Helicobacter pylori-induced mucosa-associatedlymphoid tissue and gastric lymphoma

Infection with Helicobacter pylori (Hp) induces the formation of lymphoid t issue in the stomach and the occasional development of primary gastric B-ce ll lymphomas. We have studied the expression of 2 chemokines that attract B lymphocytes, BCA-1 and SLC, in gastric tissue samples obtained from patien ts with chronic gastritis induced by Hp infection or nonsteroidal anti-infl ammatory drugs, as well as from patients with Hp-associated low-grade and h igh-grade gastric lymphomas. High-level expression of BCA-1 and its recepto r, CXCR5, was observed in all mucosal lymphoid aggregates and in the mantle zone of all secondary lymphoid follicles in Hp-induced gastric mucosa-asso ciated lymphoid tissue (MALT). Follicular dendritic cells and B lymphocytes are possible sources of BCA-1, which is not expressed by T lymphocytes, ma crophages, or CD1a(+) dendritic cells. Strong expression of BCA-1 and CXCR5 was also detected in the transformed B cells of gastric MALT lymphomas. By contrast, SLC was confined almost exclusively to endothelial cells in and outside the lymphoid tissue. Only scant, occasional SLC expression was obse rved in the marginal zone of MALT follicles. Our findings indicate that BCA -1, which functions as a homing chemokine in normal lymphoid tissue, is ind uced in chronic Hp gastritis and is involved in the formation of lymphoid f ollicles and gastric lymphomas of the MALT type.