Expression of lymphocyte homing receptors and vascular addressins in low-grade gastric B-cell lymphomas of mucosa-associated lymphoid tissue

In this study, we examined lymphocyte homing receptor and vascular addressin expression in a case of primary gastric B-cell lymphoma of mucosa- associated lymphoid tissue (MALT) with a secondary intestinal spread. We compared the findings with that observed in B cells of normal MALT and MALT acquired as a consequence of Helicobacter pylori-associated gastritis and other low-grade gastric B-cell MALT lymphomas. The neoplastic B cells in the gastric tumor were α₄β₇^-, CD62L⁺, whereas the intestinal secondary was α₄β₇⁺, CD62L^-. Incubation of isolated tumor cells from the stomach by H. pylori generated T-cell-dependent proliferation of neoplastic B cells and induced expression of α₄β₇ integrin similar to the in o testinal tumor. These observations indicate that reversal of homing receptor profile in the gastric tumor by antigen specific stimulation may be responsible for secondary intestinal dissemination. In normal stomach and normal MALT, α₄β₇ and CD62L expression reflected the differentiation of the B cell. Plasma cells were α₄β₇⁺, CD62L^-, whereas a subset of memory B cells were α₄β₇⁺, CD62L⁺. Homing receptor expression in MALT lymphoma B cells was heterogeneous, however, in line with their memory B-cell phenotype in the majority of cases, the neoplastic B cells were α₄β₇^-, CD62L⁺. Neoplastic plasma cells were always α₄β₇⁺, CD62L^-. The venules in normal gastric mucosa expressed mucosal addressin cell adhesion molecule-1 but not peripheral lymph node addressin. In normal MALT, H. pylori-associated follicular gastritis and MALT lymphomas high endothelial venules coexpressed mucosal addressin cell adhesion molecule-1 and peripheral lymph node addressin. These findings suggest expression of lymphocyte homing receptors by B cells and vascular addressins by mucosal venules are similar in normal MALT and MALT lymphomas, and factors controlling normal mucosal B-cell traffic are also operational in MALT lymphomas.