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

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Abstract
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.