CD200 Expression in Non-Myeloma Immunoproliferative Disorders
Horatiu Olteanu, Alexandra M Harrington, Steven H Kroft. Medical College of Wisconsin, Milwaukee, WI
Background: 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.
Design: 59 diagnostic bone marrow (BM) aspirates (49 MGUS, 7 LPL, and 3 PBL) were evaluated by 4-color FC with antibodies against CD19, CD20, CD38, CD45, CD56, CD117, CD200, 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 123 PCM BM aspirates.
Results: 26/49 (53.1%) MGUSs, 2/7 (28.6%) LPLs, and 1/3 (33.3%) PBLs were CD200(+). CD200 expression was found in 25/45 (55.6%) non-IgM MGUSs (IgG or IgA) and 1/4 (25%) IgM MGUSs. Comparative clinicopathologic parameters for all MGUS cases, based on CD200 expression status, are summarized in Table 1, and show no differences between the two groups. 76/123 (61.8%) PCMs were CD200(+). The proportion of CD200(+) MGUSs and PCMs was not significantly different (p=0.307).
Conclusions: 53% of MGUS in our series are CD200(+) by FC, comparable to the proportion of CD200(+) PCMs reported in our study (61%) 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.
|n (%), MGUS||26 (53.1%)||23 (46.9%)|
|Age, ≥65 years||73.1%||52.2%||0.151|
|Hgb (g/dL), median||12.7||13.2||0.879|
|WBC (x10e3/uL), median||6.47||6.62||0.833|
|Platelets (x10e3/uL), median||226||229||0.518|
|M-protein (g/dL), median||0.49||0.75||0.341|
|Core biopsy cellularity, median||30%||40%||0.262|
|% BM PCs, median||4%||3%||0.135|