CD200 and prognosis in chronic lymphocytic leukemia: Conflicting results

CD200 is a transmembrane type Ia glycoprotein belonging to theimmunoglobulin superfamily [1].It isexpressed byvariouscell types,such as B cells, a subset of T cells including activated T cells, thymo-cytes, endothelial cells, and neurons. CD200 surface expression hasbeenshowntohavearelevantroleinthedifferentialdiagnosisofB-cellchronic lymphoproliferative disorders (B-CLPDs) [2]. The major con-tributionofCD200istheabilitytodiscriminatebetweenchroniclym-phocytic leukemia (CLL) and mantle cell lymphoma (MCL), and be-tweenhairycellleukemiaanditsvariantform[3].Furthermore,ithasbeenalsodemonstratedaroleofCD200inthedifferentialdiagnosisofother forms of B-CLPDs, when incorporated in panels including othersurface markers [4,5]. However, little is known about the prognosticsignificanceofCD200expressioninCL