Human LAP(+)GARP(+)FOXP3(+) regulatory T cells attenuate xenogeneic graft versus host disease

Wang, Huihui; Song, Hyo; Pham, Anha V.; Cooper, Laurence J.; Schulze, Janika J.; Olek, Sven; Tran, Dat Q.

FOXP3 + regulatory T cells (Tregs), a subset of CD4 + T cells, maintain immune homeostasis and prevent autoimmunity by suppressing auto-reactivity and regulating immune responses to foreign and self-antigens [1] . A hallmark of Tregs is their expression of the transcription factor, FOXP3, and the high level of CD25, the IL2 receptor alpha chain [2] . Due to their role in maintaining immune homeostasis and tolerance, Tregs have been considered as potentially immunotherapy to prevent a variety of immunological diseases in human. Among potential diseases that may be tackled with such immune-modulators are most graft versus host disease (GVHD), a frequent and often severe complication following allogeneic hematopoietic cell transplantation [3] . Murine studies have demonstrated convincing evidence of the power of Tregs as a cell therapy to prevent and treat various Ivyspring International Publisher immunological conditions, such as multiple sclerosis, GVHD, inflammatory bowel disease and lupus [4] [5] [6] [7] [8] [9] [10] . In translating these studies to human therapeutic applications, one major limitation is the expansion of Tregs ex vivo to achieve consistently sufficient number and purity of bona fide Tregs. In the peripheral blood of healthy adults, there are ~5-10% FOXP3 + Tregs within total CD4 + T cells. Since FOXP3 is an intracellular transcription factor, only the CD4 + T cells with low CD127 and high CD25 expression, i.e., no more than 2-4% can be sorted to functionally isolate >90% FOXP3 purity. However, this population is not homogeneously Tregs, particularly in diseases where these markers are less correlative due to activated T cells. It has been established that there are two subsets of Tregs: those developed in the thymus (tTregs) and those generated in the periphery (pTregs). Moreover, naïve CD4 + T cells can be induced in vitro with TCR stimulation in the presence of TGFβ1 and IL2 to express FOXP3 (iTregs) [11] . The functional patterns for these different subgroups of Tregs are widely varying during the expansion of Tregs over a [3] [4] week period. In addition, the purity and composition of Tregs frequencies with respect to tTregs, iTregs, pTregs and CD4 + FOXP3 − nonTregs are also varying, resulting in an impure Treg product.