Intravenous Infusion of Syngeneic Apoptotic Cells by Photopheresis Induces Antigen-Specific Regulatory T Cells

Abstract

The basis of extracorporeal photopheresis is the reinfusion of leukocytes previously exposed to 8-methoxypsoralen (8-MOP) and UVA radiation. It has been approved for the palliative treatment of cutaneous T cell lymphoma and has reported benefits in autoimmune diseases, transplant rejection, and graft-vs-host disease. However, the underlying mechanism of photopheresis remains unresolved. Because UVB radiation can cause immune tolerance via induction of regulatory T cells, we studied whether photopheresis exerts a similar effect extracorporeally. Therefore, we established a model of photopheresis using a murine model of contact hypersensitivity. Splenocytes and lymph node cells of mice that were sensitized with dinitrofluorobenzene were exposed to 8-MOP plus UVA in vitro. Intravenous injection of these cells into naive mice caused inhibition of a hapten immune response, which was lost upon depletion of CD11c+ cells but not T cells. Mice that received untreated cells or cells exposed to UVA or 8-MOP alone were not affected. Inhibition was cell-mediated and Ag-specific as demonstrated by transfer of tolerance from the primary recipients into naive animals, which could, however, properly respond to the unrelated hapten oxazolone. Transfer activity was lost when cells were depleted of CD4+ or CD25+ subpopulations. These data suggest that photopheresis exerts its immunomodulatory effects via the induction of Ag-specific regulatory T cells.

Suppression of FVIII Inhibitor Formation in Hemophilic Mice by Delivery of Transgene Modified Apoptotic Fibroblasts

“…[19][20][21] Notably, it has been shown that the immune response to a foreign antigen can also be suppressed by delivering it systemically in association with syngeneic ACs. [22][23][24] In this study, we demonstrate that infusion of apoptotic syngeneic fibroblasts modified to express a hFVIII transgene significantly inhibits the immune response against hFVIII in both naive and preimmunized hemophilic mice. Furthermore, we show that the hyporesponsiveness to hFVIII is associated with the generation of antigen-specific Tregs.…”

Photopheresis with UV-A light and 8-methoxypsoralen leads to cell death and to release of blebs with anti-inflammatory phenotype in activated and non-activated lymphocytes

“…The activity of caspase-3 and DNA ladder formation increases after UV-A irradiation leading to cellular death [25]. It was previously shown that intravenous injection of PUVA treated cells exerts silencing of the immune system by inducing regulatory T cells [19]. The anti-inflammatory cytokine IL-10 was identified as critical inhibitory component in the sensitization and effector phase of contact hypersensitivity [18].…”

Infusion of UVB-treated splenic stromal cells induces suppression of β cell antigen-specific T cell responses in NOD mice

“…This finding also underscores the possibility of utilizing a type of universal apoptotic cell, such as apoptotic PBMCs in clinics for inducing immune tolerance to the targeted antigens including self-antigens in autoimmune diseases and MHC antigens in allogeneic transplantations. Indeed, Maeda et al [11] reported that intravenous injection of apoptotic syngeneic splenocytes led to immune tolerance specific to DNFB antigens simultaneously administered to the skin during induction of contact hypersensitivity. Recent evidence has also shown that T1D patients benefited from photopheresis, which is proposed to be associated with photopheresis-induced apoptosis of blood cells [26].…”

“…Thus, it is necessary to find alternative techniques in utilizing apoptotic cells to induce β cell antigen-specific T cell tolerance. Recently, it was reported that intravenous injection of apoptotic syngeneic splenocytes along with administration of a hapten, 2,4,dinitrofluorobenzene (DNFB) to the skin induced immune tolerance specific to DNFB [11]. This study suggests that it is possible to utilize apoptotic non-β cells, such as splenocytes or peripheral blood mononuclear cells to induce immune tolerance to β cell antigens with the exposure of endogenous β cell antigens during the process of autoimmunity, thereby preventing autoimmune diabetes.…”

“…It has also been shown that steady state apoptotic cells can trigger phagocytes to secrete immunosuppressive cytokines, such as IL-10 and TGF-β [7,8], which in turn facilitate the development of regulatory T cells [9]. Due to this unique relationship between apoptotic cells and immune tolerance, apoptotic cells have been employed with success in inducing immune tolerance to allogeneic antigens [10] and other exogenous antigens [11].…”