CXCR3‐positive B cells found at elevated frequency in the peripheral blood of patients with MALT lymphoma are attracted by MIG and belong to the lymphoma clone

Chemokine receptors mediate the migration of lymphocytes through binding of their ligands. CXCR3 is expressed in Th1 T cells; however, CXCR3 was recently reported in B‐cell mucosa‐associated lymphoid tissue (MALT)‐type lymphoma and splenic marginal zone lymphoma. To investigate whether CXCR3‐positive B lymphocytes in peripheral blood (PB) migrate to MALT and spleen, and whether the lymphoma clone is present in PB, we studied 16 cases of MALT lymphoma. In MALT cases, CXCR3‐positive B lymphocytes in PB could migrate to MIG, the CXCR3 ligand. Immunohistochemical analysis showed that MALT lymphoma cells expressed CXCR3, whereas epithelial glands and/or stromal cells expressed MIG. In the PCR analysis for VH gene rearrangements, MALT lymphoma showed monoclonal or oligoclonal bands. In addition, in 8 of 16 MALT cases, the VH gene rearrangement of MALT lymphoma had the same bands as the CXCR3‐positive B lymphocytes in PB. In 4 cases, the same clones of DNA sequences were confirmed in MALT lymphoma and CXCR3‐positive B lymphocytes of PB. The findings support the theory that CXCR3‐positive B lymphocytes in PB of MALT patients belong to the lymphoma clone and migrate to MIG‐expressing mucosa‐associated lymphoid tissue. It seemed to be associated with the dissemination of MALT lymphoma. © 2004 Wiley‐Liss, Inc.