Description
CD200 is a member of the immunoglobulin type 1 superfamily that is highly expressed in the central nervous system, dendritic cells, and lymphocytes. CD200 is functionally involved in an immunosuppressive signaling pathway via interaction with its receptor, CD200R, with downstream effects of macrophage inhibition, induction of regulatory T cells, and inhibition of tumor-specific T cells. In addition to being expressed in normal tissues, CD200 has also been demonstrated in solid tumors5 and hematologic malignancies, such as acute leukemias, chronic lymphocytic leukemia/small lymphocytic lymphoma, hairy cell leukemia, mediastinal large B-cell lymphoma, classic Hodgkin lymphoma, and angioimmunoblastic T-cell lymphoma. In addition, neoplastic plasma cells frequently upregulate CD200 expression, as demonstrated by the large proportion of CD200+ plasma cell myeloma (PCM) cases (approximately 70%) found on gene expression profiling and flow cytometry. In contrast, normal plasma cells are CD200