Increasing the applicability of transplantation tolerance in solid organs by leveraging linked suppression

Abstract

Objectives: To investigate differences in immune responsiveness of islet allograft recipients before and after ADL infusion-based tolerance protocol. To understand the implications of MHC-I and MHC-II matching on linked suppression.Methodology: Peripheral blood mononuclear cells were collected from a cohort of 5 nonhuman primates who underwent islet transplantation after two peritransplant infusions of apoptotic donor leukocytes under the cover of short-term immunotherapy with anti-CD40 antibody, rapamycin, soluble tumor necrosis factor receptor and anti-IL-6R antibody between posttransplant day 60 and 90. Recipient PBMCs were cocultured with irradiated donor PBMC from the tolerized islet donor DR matched to the recipient (Donor DR Match), unrelated class I MHC allele matched donor (3P Class I Match), unrelated class II MHC allele matched donor (3P Class II Match), and unrelated MHC complete mismatched donor (Complete Mismatch) in a 5-day mixed leukocyte reaction. Both flow cytometry and cytometry by time of flight were used for data acquisition. Results: When recipient PBMCs treated with ADL infusion and short course immunotherapy was challenged with third-party antigen matched at either MHC-I (3P Class I) or MHC-II (3P Class II) to Donor DR, we again observed a near 2-fold increase in the Treg and Tr1 populations, providing evidence of linked suppression. Both third-party MHC matched conditions were associated with an increase in regulatory CD4 cell subsets and decreased CD4 and CD8 effector T cells compared to challenge with complete mismatched antigen. Conclusion: For the first time, we demonstrate linked suppression in a large animal model. Our study pointed to a slight trend of class II MHC matching showing greater expansion of Treg population compared to class I MHC matching that was consistent with the literature.