Interleukin-2-Producing CD4+OX40+ T Cell as a Target for the Treatment of Chronic Graft-Versus-Host-Disease.
Authors: Shindo Takero , Ishikawa Takayuki , Fukunaga Akiko , Hori Toshiyuki , Uchiyama Takashi 
Published: April 2020

Abstract
Chronic graft-versus-host-disease (GVHD) after allogeneic hematopoietic stem cell transplantation (allo-HSCT) is a serious complication, for which limited therapeutic approaches exist. Thymus-derived autoreactive as well as alloreactive T cells are shown to be involved in the development of chronic GVHD and CD4+ T cells are regarded to play a central role. OX40 (CD134) is known to play an important role in co-stimulation and survival elongation of CD4+ T cells, and murine models revealed that the interaction of OX40/OX40-ligand constitutes an essential parts in autoimmune and alloimmune responses. Since we showed that the increase of CD4+OX40+ T cells in peripheral blood of allo-HSCT recipients precedes the occurrence of chronic GVHD (Kotani A et al. Blood2001; 98: 3162–4), we have paid attention to the role of peripheral blood CD4+OX40+ T cells in the development of chronic GVHD. To further know the characteristics of peripheral blood CD4+OX40+ T cells from patients after allo-HSCT, we analyzed surface phenotype and the ability of cytokine production of CD4+ T cells from 25 allo-HSCT recipients. A majority of CD4+OX40+ T cells showed CD45RO+CD62L+CCR7+, while CD4+OX40− T cells were mainly CD45RO+CD62L−CCR7−. When stimulated with PMA and ionomycin, a significant part of CD4+OX40+ T cells produced interleukin-2 (IL-2). In contrast, a majority of CD4+OX40−HLA-DR+ T cells, the ratio of which also increased in peripheral blood of allo-HSCT recipients, produced interferon-γ (IFN-γ). Thus, the pattern of the expression of activation antigens on CD4+ T cells is a landmark of the potential to produce IL-2 or IFN-γ. When clinical data were combined, patients suffering from chronic GVHD showed increased ratio of IL-2-producing CD4+OX40+ T cells among CD4+ T cells (more than 10%). In fact, it correlates more closely (p=0.016) to the occurrence of chronic GVHD than the ratio of CD4+OX40+ T cells or that of IL-2-producing CD4+ T cells (p=0.06). Interestingly, the ratio of IFN-γ-producing CD4+ T cells does not correlate (p=0.95), suggesting that they do not contribute to the process of ongoing chronic GVHD. As CD4+OX40+ T cells share the characteristics of central memory T cells, we hypothesized that CD4+OX40+ T cells, which home secondary lymphoid organs, are stimulated with antigens and develop into effector cells, some of which induce chronic GVHD. Then we collected CD4+ T cells from recipients of allo-HSCT and sorted them into OX40+ and OX40− fractions. When sorted cells were stimulated with immobilized anti-CD3 and soluble anti-CD28 (CD3/28 stimulation), IL-2-producing cells were detected mainly in OX40+ fraction and IFN-γ-producing cells were abundantly and exclusively observed in OX40− fraction. When sorted cells were stimulated with CD3/28 for 48 hr, followed by 4-day cultivation with IL-2, OX40+ cells showed vigorous growth without reducing viability. In addition, re-stimulation with CD3/CD28 revealed that OX40+ cells produce a large amount of IFN-γ or IL-4. In this way, peripheral blood CD4+OX40+ T cells have potential to easily differenciate into effector cells, which may contribute to the development of chronic GVHD. The signaling from OX40 may also accelerate this process. Targeted therapy against IL2-producing CD4+OX40+ T cells may afford a breakthrough in the treatment of chronic GVHD.