Transforming Growth Factor Beta (Tgf Beta) Plays A Crucial Role In Prolonging Allograft Survival In An Allodepletion ("Pruning") Skin Transplant Model

Adoptive cell therapies involving cell manipulation to achieve tolerance are increasingly being studied in animal models and in human trials. We have demonstrated that the specific removal of allo-stimulated dividing cells (or "pruning") promotes long-term allograft survival across a major MHC mismatch in transplant models including skin, heart and islet transplants. In this study, we examine the role of transforming growth factor beta (TGF beta), an important regulatory cytokine, on allograft survival in our allodepletion or "pruning" skin transplant model. Increased proliferation of CD4(+) T cells was observed following allo-stimulation of BALB/c spleen cells (labeled with CFSE) in the presence of the regulatory cytokines Tap and (interleukin-2) IL-2 in a mixed lymphocyte culture (MLC). Expression of the regulatory gene forkhead box-3 (FoxP3) was increased in both the allo-stimulated non-dividing (ND) (CFSEhigh) and dividing (D) (CFSElow) CD4(+) T cell populations, with the highest expression found in the D CD4(+) T cell population. Mice reconstituted with allo-stimulated ND CD4(+) T cells following TGF beta/IL-2 stimulation showed prolonged allograft survival, similar to previous data. Significantly, TGF beta/IL-2 stimulation prevented acute rejection of allografts across a major MHC mismatch in the presence of highly activated allo-stimulated D CD4(+) T cells. Blockade of TGF beta promoted rejection of allografts even following depletion of allo-stimulated D CD4(+) T cells. These studies support a crucial role for TGF beta in the survival of allografts and shows that regulatory cytokines TGF beta/IL2 can delay the rejection of allografts, even in the presence of highly activated alloreactive T cells. (C) 2014 Elsevier B.V. All rights reserved.