Increased circulating CD4 + FOXP3 + T cells associate with early relapse following autologous hematopoietic stem cell transplantation in multiple myeloma patients.

We investigated dynamics of CD4+ FOXP3+ T cell recovery following the high-dose chemotherapy (HDC) with autologous hematopoietic stem cell transplantation (auto-HSCT) in multiple myeloma (MM) patients. Circulating CD4+ FOXP3+ T cells of 79 MM patients were evaluated using flow cytometry before HDC with auto-HSCT, at the day of engraftment, and following 6 and 12 months. Percentage of CD4+ FOXP3+ T cells restored rapidly following auto-HSCT, became higher than pre-transplant level at the day of engraftment and then subsequently decreased for a year. CD4+ FOXP3+ T cells at the time of engraftment were increased in patients with the relapse or progression of MM during 12 months following auto-HSCT (n=10) compared to non-relapsed patients (n=50): 6.7% (5.3-8.9%) vs 4.9% (2.8-6.6%); PU = 0.026. Area under the curve was 0.72 (95% CI: 0.570-0.878; р=0.026). Circulating CD4+ FOXP3+ T cell count was not associated with the percentage of myeloma plasma cells in a bone marrow but depended on its amount in autografts.

Conclusions: Relative count of CD4+ FOXP3+ T cells restored rapidly following auto-HSCT (at the day of engraftment), became higher than pre-transplant level and then subsequently decreased for a year. Their excess at the time of engraftment is associated with early relapse.