Abstract

Background: Chronic lymphocytic leukemia (CLL) is a malignancy of mature B-lymphocytes characterized by their accumulation in the bone marrow and peripheral blood. CD200 is an immune checkpoint molecule critical for immune tolerance, and its overexpression has been associated with tumor progression through immune evasion mechanisms, particularly via interaction with CD200R. Aims of the Study: To assess plasma levels of soluble CD200 (sCD200) in newly diagnosed CLL patients compared to healthy individuals. To correlate sCD200 levels with disease stage, hematological parameters, and prognostic markers: β2-Microglobulin (β2M) and Leukocyte Associated Immunoglobulin-like Receptor-1 (LAIR-1). Methods: This cross-sectional study was conducted over six months (Dec 2023 – May 2024) at Baghdad Teaching Hospital and involved 68 adult patients newly diagnosed with CLL (age range: 42–83 years) and 20 healthy controls. Diagnosis relied on morphology and flow cytometry. The Binet staging system was used for clinical classification. Plasma levels of sCD200 and β2M were measured via ELISA. Results: Plasma CD200 and β2M levels were significantly elevated in CLL patients compared to controls (p=0.001). Statistically significant differences across Binet stages were observed in plasma CD200, β2M, Hb, WBC, ALC, and platelet counts (p-values: 0.01–0.001). No significant differences were found for SCs% and age. CD200 positively correlated with β2M (p=0.02). LAIR-1 expression showed no association with CD200 or β2M levels. Conclusions: CLL patients exhibited significantly elevated plasma CD200 levels, which increased with disease progression. CD200 also correlated positively with β2M. No association was found with LAIR-1 expression or SCs%.