Interleukin-2 is associated with cytopenias in systemic lupus erythematosus

Interleukin 2 (IL-2) is a cytokine essential for the development and function of regulatory T cells, which are key players in maintaining immune tolerance by suppressing autoreactive lymphocytes. Patients with systemic lupus erythematosus (SLE) often exhibit reduced IL-2 production, resulting in impaired Treg function and a consequent breakdown of immune tolerance. Hematological abnormalities, mainly leukopenia and lymphopenia, are prominent features of SLE. This study aimed to explore the relationship between serum IL-2 concentrations and the altered blood cell populations observed in patients with SLE. We recruited 235 patients with SLE. Complete blood counts, including red blood cells, white blood cells, and platelets, were obtained, and IL-2 levels were quantified using the ultrasensitive single-molecule array (Simoa) technique. Multivariate linear and logistic regression analyses were performed to evaluate the associations between IL-2 concentrations and hematological parameters. Multivariate linear regression revealed significant inverse associations between the serum IL-2 concentration and the hemoglobin level, hematocrit, mean corpuscular hemoglobin concentration, and total leukocyte, neutrophil, lymphocyte, and basophil counts. Similarly, after adjustment for covariates, serum IL-2 was associated with increased odds of anemia, leukopenia, and lymphopenia but not neutropenia or thrombocytopenia. In conclusion, circulating IL-2 levels are independently associated with specific hematological abnormalities, including anemia, leukopenia, and lymphopenia, in patients with SLE. These findings highlight the potential role of IL-2 and regulatory T cell dysfunction in the hematologic manifestations of SLE.