Association of circulating regulatory T cell number with the incidence and prognosis of diffuse large B ‐cell lymphoma

Regulatory T ( T reg) cells are essential for maintaining immune tolerance. High T reg frequencies have been reported in peripheral blood and tissue samples of patients with solid tumors while their role in lymphomas, including diffuse large B ‐cell lymphoma ( DLBCL ) has not been clearly established. In this study, we analyzed the circulating T reg numbers in 27 patients with newly diagnosed DLBCL and 17 healthy individuals. Tregs were detected by flow cytometry based on CD 4 + CD 25 high F ox P 3 + phenotype. In addition, the expression of CD 45 RA , HLA ‐ DR , CD 62L, CD 39, and CTLA 4 was analyzed. The number of circulating T reg cells was lower in patients with DLBCL than in healthy controls: median 23 (range, 4–107)/μL vs. 41 (19–104)/μL ( P  = 0.04). In particular, the number of T regs expressing CD 45 RA (naïve Tregs), HLA ‐ DR (marker of activation), and CD 62L ( L ‐selectin) was decreased in the DLBCL group. Lower (below median) number of circulating Tregs was associated with reduced chance of achieving complete remission (29% vs. 69%, P  = 0.05) and reduced probability of even‐free survival (24% vs. 84% at 1 yr, P  = 0.0004), independently on the International Prognostic Index. We conclude that low number of circulating Tregs may be associated with poor prognosis in patients with DLBCL . However, our observations require confirmation in larger patient population.