Plasma interleukin-22 and its cellular receptor (IL-22RA1) expression in chronic lymphocytic leukemia

Background: Chronic lymphocytic leukemia (CLL) is an environment-dependent hematologic malignancy where interactions with accessory cells through cytokines and their receptors seem to confer a survival advantage, thus contributing to disease progression. Interleukin-22 (IL-22) is a T-cell-derived cytokine that promotes cell proliferation and survival through interaction with its receptor IL-22RA1, normally absent in normal immune cells, including B and T lymphocytes. Aim: This study aimed to determine the plasma levels of IL-22 and the expression of IL-22RA1 on malignant cells in patients with B-cell CLL (B-CLL), together with their relation to clinical and prognostic characteristics of the disease. Patients and methods: The study was carried out on 62 newly diagnosed B-CLL patients. Twenty-five age-matched and sex-matched healthy individuals served as controls. Patients were diagnosed, according to the International Workshop on CLL guidelines, by cytomophology, immunophenotyping, conventional cytogenetic analysis, and fluorescence in-situ hybridization. Plasma IL-22 levels were measured by an enzyme-linked immunosorbent assay and the expression of IL-22RA1 on leukemic cells was assessed by flow cytometry. Results: Plasma IL-22 was significantly higher in B-CLL patients (range, undetectable 62.9 pg/ml; median, 6.6) compared with control participants (range, undetectable 6.4 pg/ml; median, undetectable) (P 0.01). IL-22RA1 expression was negative in all normal controls, whereas in B-CLL patients it was positively expressed in 35/62 CLL cases (56%). Taking the median level of IL-22RA1 expression in CLL patients as a cutoff level, overexpression (≥10%) was observed in 32/62 (52%) cases. IL-22RA1 expression correlated significantly positively with plasma levels of IL-22 (rs=0.817; P 0.01). Patients presenting with high CD38 expression had significantly higher plasma IL-22 levels compared with those with low CD38 (undetectable 62.9 pg/ml; median, 19.3 vs. undetectable 50.1 pg/ml; median, 3.1) (P 0.01) as well as overexpression of IL-22RA1. No significant relation could be established between either plasma IL-22 levels or IL-22RA1 expression with other clinical features or prognostic criteria of CLL. Conclusion: This is the first report to describe the aberrant expression of the IL-22 signaling pathway in B-CLL and to link its overexpression with high CD38 expression, a known poor prognostic marker of the disease.