The chemokine receptor CXCR3 is expressed in a subset of B-cell lymphomas and is a marker of B-cell chronic lymphocytic leukemia

Chemotaxis in leukocytes is mediated through binding of soluble chemokines to transmembrane G-protein coupled receptors. The chemokine receptor CXCR3 has been previously shown to be widely expressed on activated T cells and t o mediate T-cell chemotaxis on binding to various ligands, including Mig, I P-10, and ITAC. By using immunohistochemical end flow cytometric analysis, we report that CXCR3 is also expressed on a subset of peripheral blood B ce lls and in distinct subtypes of B-cell lymphoma. CXCR3 immunohistochemical or flow cytometric expression was seen in 37 of 39 cases of chronic lymphoc ytic leukemia/small lymphocytic lymphoma (diffusely positive in 33 cases), whereas mantle cell lymphoma (30 cases), follicular lymphoma (27 cases), an d small noncleaved cell lymphoma (8 cases) were negative in all but 2 cases . Strong CXCR3 expression was also seen in splenic marginal zone lymphoma ( 14 of 14 cases) and in the monocytoid and plasmacytic cells in extranodal m arginal zone lymphoma (15 of 16 cases). This differential expression of CXC R3 in B-cell tumors contrasts with that of another B-cell-associated chemok ine receptor, BLR1/CXCR5, which we show here is expressed on all types of B -cell lymphoma tested. We also report that the CXCR3 ligand, Mig, is coexpr essed on tumor cells in many cases of CLL/SLL (10 of 13 cases examined) wit h Mig expression less frequently seen in other B-cell lymphoma subtypes, Co expression of CXCR3 and its ligand, Mig, may be an important functional int eraction in B-CLL, as well as a useful diagnostic marker for the differenti al diagnosis of small cell lymphomas.