Altered dynamics of T cell subsets in peripheral blood impacts disease progression in newly diagnosed multiple myeloma.

T cells are essential for tumor immunosurveillance and disease regulation in Multiple Myeloma (MM), but their role in disease pathogenesis is not well understood. To investigate this, we analyzed T cell subsets for activation status, relative distribution of naïve and memory T cell populations, regulatory T cells (Tregs), and circulating follicular helper T cells (cTFH) in the peripheral blood of 40 newly diagnosed MM (NDMM) patients. We also assessed inhibitory receptor expression CD160, ICOS/CD278, CD152/CTLA-4, and PD-1/CD279 on T cells in peripheral blood. Our results showed reduced T cell numbers, an imbalance between naïve and effector CD4+ T cells, and decreased memory Tregs in newly diagnosed MM patients compared to healthy controls. Furthermore, plasma cells in the bone marrow correlated with percentage of activated cTFH cells and inhibitory receptor expressing T cells in peripheral blood indicating that disrupted T cell homeostasis and immune-mediated processes may drive disease progression in NDMM.