Study of CD200 in chronic lymphocytic leukemia

Background: CD200 is a transmembrane protein expressed on multiple cell types (e.g. thymocytes, activated T cells, B cells, dendritic cells, and endothelial cells). It regulates antitumor immunity and its overexpression is associated with poor prognosis in chronic lymphocytic leukemia (CLL). A soluble variant of CD200 (sCD200) is detectable in human serum, and an elevated serum level was shown in patients with CLL. Objective: The aim of the study is to investigate the relationship between the levels of CD200 and clinical staging in patients with CLL. Subjects and methods: The study included 50 patients, divided into two groups. The patient group included 30 de-novo patients with CLL (18 men and 12 women), whose age ranged from 49 to 70 years with a mean±SD of 57.82±4.94 years. They were classified according to the modified Rai staging system into three classes: (a) low-risk patients, which included seven cases (stage 0); (b) intermediate-risk patients, which included eight cases (stages I and II); and (c) high-risk patients, which included 15 cases (stages III and IV). The control group included 20 individuals (14 men and six women), whose age ranged from 50 to 72 years with a mean±SD of 58.54±5.1 years. CD200 levels were measured by flow cytometry. Results: Higher levels of CD200 were observed in the patient group compared with the control group. In addition, there was a significant increase of CD200 expression in the intermediate group of patients compared with low-risk patients, and a significant increase in the CD200 level in the high-risk group compared with intermediate-risk patients. Conclusion: A positive correlation between the level of CD200 expression and clinical staging system of CLL was observed in our study; thus, measurement of CD200 may have a prognostic role in patients with CLL. In addition, it can be used as a follow-up marker for clinical response to treatment in CLL. CD200 blockade by immunotherapeutic agents may represent a novel approach for clinical treatment of CLL and a number of B-cell-derived neoplasms.