Immunoregulatory Subpopulations of iNKT Cells and Myeloid-Derived Suppressor Cells in Chronic Lymphocytic Leukemia: Implications for Disease Progression and Immune Evasion

Chronic lymphocytic leukemia (CLL) is characterized by progressive immune dysregulation. Invariant natural killer T (iNKT) cells support immune surveillance, but the clinical relevance of their regulatory subsets remains unclear. FoxP3⁺ regulatory iNKT cells (iNKTreg) and E4BP4⁺IL-10⁺ (iNKT10) cells may reflect immunoregulatory changes associated with disease progression. The study aimed to quantify circulating iNKTreg and iNKT10 subsets and monocytic myeloid-derived suppressor cells (M-MDSCs) in treatment-naïve CLL patients and evaluate their associations with disease characteristics and time to first treatment (TTFT).

Peripheral blood samples from 60 untreated CLL patients and 20 healthy donors were analyzed by flow cytometry to determine iNKTreg and iNKT10 percentages, as well as indoleamine 2,3-dioxygenase (IDO)-expressing M-MDSCs. Receiver operating characteristic (ROC) curves and Cox proportional hazards models were used to assess prognostic significance.

iNKTreg and iNKT10 percentages were significantly increased in CLL compared with healthy donors (p = 0.002). Elevated iNKTreg frequencies were associated with zeta-chain-associated protein of 70 kD (ZAP-70) positivity (p = 0.017), CD38 positivity (p = 0.048), and treatment requirement during follow-up (p = 0.016). Based on an ROC-derived cut-off of 9.6% (AUC = 0.753), patients with iNKTreg ≥ 9.6% had shorter TTFT (hazard ratio [HR] = 2.71; 95% confidence interval [CI], 1.13–6.49; p = 0.025), although the association was not retained in multivariate analysis (HR = 1.27; 95% CI, 0.44–3.64; p = 0.626). iNKTreg and iNKT10 percentages correlated positively with IDO⁺ M-MDSCs (p = 0.035 and p = 0.044), but not with arginase-1 (ARG1) or inducible nitric oxide synthase (NOS2).

Elevated iNKTreg levels reflect a more aggressive disease phenotype and associate with shorter TTFT in univariate analysis, supporting their exploration as complementary immunological biomarkers in CLL. Functional studies and validation in larger cohorts are needed to determine their prognostic and biological significance.