EXPRESSION OF NKG2 RECEPTORS ON CYTOTOXIC LYMPHOCYTES IN PATIENTS WITH MULTIPLE MYELOMA

This study assessed the expression of NKG2 family receptors (NKG2A, NKG2C, NKG2D) on cytotoxic T lymphocytes and NK cells from peripheral blood of patients with multiple myeloma (MM) compared to healthy donors. The relevance of this work is due to the important role of the HLA‑E/NKG2 axis in the mechanisms of tumor immune evasion in MM, as well as the potential for therapeutic blockade of these receptors. The study included 10 patients with MM (stage II–III according to Durie–Salmon, in remission) and 9 conditionally healthy donors. Flow cytometry was used to determine the relative abundance of NK cell subpopulations (CD16−CD56+, CD16+CD56+, CD16+CD56−) and CD3+CD4− cytotoxic T lymphocytes expressing NKG2A, NKG2C, and NKG2D. It was found that, compared to donors, MM patients had a significantly higher proportion of NKG2A+ cells among mature CD16+CD56+ NK cells (median 23.8% vs. 7.5%) and among CD16+CD56− NK cells (10.7% vs. 2.1%). At the same time, the proportion of CD3+CD4− cytotoxic T lymphocytes expressing the activating receptor NKG2C was reduced in MM (1.9% vs. 4.6% in donors). The relative abundance of cells expressing NKG2D did not differ between groups for either NK cells or T lymphocytes. These data indicate a shift in balance toward predominance of the inhibitory receptor NKG2A in the NK cell compartment and a reduction of the activating receptor NKG2C in the T‑cell compartment in multiple myeloma. This may reflect suppression of adaptive cellular immunity and contribute to tumor immune evasion. Thus, the HLA‑E/NKG2 axis represents a promising target for further study of the immunopathogenesis of hematologic malignancies and for the development of immunotherapeutic approaches aimed at restoring the function of effector lymphocytes.