CD200 Expresion in Non-Myeloma Immunoproliferative Disorders
The majority of plasma cell myelomas (PCMs) are positive for CD200, a membrane protein with immunosuppressive function. CD200 expression has been also described in non-Hodgkin B-cell lymphomas, such as chronic lymphocytic leukemia/small lymphocytic lymphoma, hairy cell leukemia, mediastinal large B-cell lymphoma, and lymphoplasmacytic lymphoma (LPL). Since there is no literature data on CD200 expression in other plasma cell dyscrasias, we studied the expression of CD200 by flow cytometry (FC) in cases of monoclonal gammopathy of undetermined significance (MGUS), LPL and plasmablastic lymphoma (PBL), and correlated expression with clinicopathologic parameters.
74 diagnostic bone marrow (BM) aspirates (61 MGUS, 10 LPL, and 3 PBL) were evaluated by 4-color FC with antibodies against CD5, CD10, CD19, CD20, CD38, CD45, CD56, CD117, CD200, and surface and cytoplasmic light chains. Expression of CD200 was assessed in plasma cells (PCs) based on an isotype control tube containing CD38. CD200 expression status in patients with MGUS was then correlated with clinical and pathologic parameters, including CBC data, immunophenotype, BM morphology, and cytogenetics. For comparison, we evaluated CD200 expression in 74 newly diagnosed PCM BM aspirates.
33/61 (54.1%) MGUSs, 2/10 (20.0%) LPLs, and 1/3 (33.3%) PBLs were CD200(+). CD200 expression was found in 32/56 (57.1%) non-IgM MGUSs (IgG or IgA) and 1/5 (20%) IgM MGUSs. Comparative clinicopathologic parameters for all MGUS cases, based on CD200 expression status, showed no differences between the two groups. 54/74 (72.9%) of newly diagnosed PCMs were CD200(+). The proportion of CD200(+) new PCMs in our series was significantly higher than that of CD200(+) MGUSs (p=0.030) and CD200(+) LPLs (p=0.002).
54% of MGUS in our series are CD200(+) by FC, which is significantly lower than the proportion of CD200(+) new PCMs reported in our study (73%) and in the literature. We also demonstrate a predominance of CD200(-) cases in a limited number of LPLs and PBLs, respectively; this is in contrast to the percentage of CD200(+) LPLs (8/10, 80%) reported in a recent immunohistochemistry study.Download the PDF