Regulatory T-cell depletion in angioimmunoblastic T-cell lymphoma.

Angioimmunoblastic T-cell lymphoma (AITL) is the most frequent nodal T-cell lymphoma and is characterized by a polymorphic lymph node infiltrate, various dysimmune disorders, and a poor prognosis. Regulatory T-cells (Treg) play an emerging role in the prognosis of non-Hodgkin B-cell lymphoma and mediate significant autoreactive T-cell suppression. In this report, we demonstrate that numbers of Treg are significantly decreased in AITL lymph nodes [n = 30, 91 (40-195) per high power fields] compared with follicular lymphoma [n = 19, 179 (86-355)] and reactive lymph nodes [n = 8, 186 (140-265)]. Moreover, the few Treg in lymph nodes of AITL are resting Treg (rTreg) and have a naive CD45RA+, PD1-, and ICOS- phenotype [n = 5, 57% of Treg are CD45RA+ (16-96)], in contrast to the Treg in follicular lymphomas [n = 5, 7.4% (1-13)] or reactive lymph nodes [n = 7, 18.6% (6-48)]. Interestingly, Treg depletion was not observed in AITL peripheral blood at diagnosis. Altogether, these data suggest that Treg depletion could contribute to the nodal neoplastic T(FH) expansion and dysimmune symptoms in AITL.