ABSTRACT
IL-2 plays a critical role in the maintenance of CD4+CD25+ FOXP3(+) regulatory T cells (Tregs) in vivo. We examined the effects of IL-2 signaling in human Tregs. In vitro, IL-2 selectively up-regulated the expression of FOXP3 in purified CD4+CD25+ T cells but not in CD4+CD25- cells. This regulation involved the binding of STAT3 and STAT5 proteins to a highly conserved STAT-binding site located in the first intron of the FOXP3 gene. We also examined the effects of low-dose IL-2 treatment in 12 patients with metastatic cancer and 9 patients with chronic myelogenous leukemia after allogeneic hematopoietic stem cell transplantation. Overall, IL-2 treatment resulted in a 1.9 median fold increase in the frequency of CD4+CD25+ cells in peripheral blood as well as a 9.7 median fold increase in FOXP3 expression in CD3+ T cells. CD56+CD3- natural killer (NK) cells also expanded during IL-2 therapy but did not express FOXP3. In vitro treatment of NK cells with 5-aza-2'-deoxycytidine restored the IL-2 signaling pathway leading to FOXP3 expression, suggesting that this gene was constitutively repressed by DNA methylation in these cells. Our findings support the clinical evaluation of low-dose IL-2 to selectively modulate CD4+CD25+ Tregs and increase expression of FOXP3 in vivo.
Subject(s)
CD4-Positive T-Lymphocytes/immunology , Forkhead Transcription Factors/genetics , Interleukin-2/therapeutic use , Leukemia, Myelogenous, Chronic, BCR-ABL Positive/immunology , Neoplasms/drug therapy , Receptors, Interleukin-2/blood , STAT Transcription Factors/physiology , T-Lymphocytes/immunology , Antigens, CD/blood , CD4-Positive T-Lymphocytes/cytology , CD4-Positive T-Lymphocytes/drug effects , Cell Division , Gene Expression Regulation/drug effects , Humans , Interleukin-2/pharmacology , Killer Cells, Natural/drug effects , Killer Cells, Natural/immunology , Leukemia, Myelogenous, Chronic, BCR-ABL Positive/drug therapy , Neoplasms/immunology , Stem Cell Transplantation , T-Lymphocytes/drug effectsABSTRACT
Chronic graft-versus-host disease (cGVHD) is a major complication of allogeneic hematopoietic stem cell transplantation but the immune mechanisms leading to the diverse clinical manifestations of cGVHD remain unknown. In this study, we examined regulatory T cells (Tregs) in 57 transplant recipients (30 with cGVHD and 27 without active cGVHD) and 26 healthy donors. Phenotypic studies demonstrated decreased frequency of CD4+CD25+ T cells in patients with cGVHD compared with patients without cGVHD (P < .001) and healthy individuals (P < .001). Gene expression of Treg transcription factor FOXP3 was reduced in cGVHD patients compared with patients without cGVHD (P = .009) or healthy donors (P = .01). T-cell receptor excision circle (TREC) assays for the evaluation of thymus activity revealed fewer TRECs in both transplant groups compared with healthy donors (P < .001 and P = .02, respectively) although no difference was observed between patients with or without cGVHD (P = .13). When tested in functional assays, Tregs from both patient cohorts and healthy individuals mediated equivalent levels of suppression. Collectively, these studies indicate that patients with active cGVHD have reduced frequencies of Tregs but the function of these cells remains normal. These findings support the development of new strategies to increase the number of Tregs following allogeneic hematopoietic stem cell transplantation to prevent or correct cGVHD.
