CXCR5+CD8+ T Cell–Mediated Suppression of Humoral Alloimmunity and AMR in Mice Is Optimized With mTOR and Impaired With Calcineurin Inhibition

Abstract

Background. Adoptive cellular therapy (ACT) with antibody-suppressor CXCR5+CD8+ T cells (CD8+ TAb-supp) inhibits alloantibody production, antibody-mediated rejection (AMR), and prolongs graft survival in multiple transplant mouse models. However, it is not known how conventional immunosuppressive agents impact the efficacy of CD8+ TAb-supp ACT. Methods. We investigated the efficacy of CD8+ TAb-supp cell ACT when combined with calcineurin inhibitor (CNi) or mammalian target of rapamycin inhibitor (mTORi) in a murine model of kidney transplant. Results. ACT-mediated decrease in germinal center B cells, posttransplant alloantibody titer, and amelioration of AMR in high alloantibody-producing CCR5 knockout kidney transplant recipients were impaired when ACT was combined with CNi and enhanced when combined with mTORi. CNi (but not mTORi) reduced ACT-mediated in vivo cytotoxicity of IgG+ B cells and was associated with increased quantity of germinal center B cells. Neither CNi nor mTORi treatment impacted the expression of cytotoxic effector molecules (FasL, Lamp1, perforin, granzyme B) by CD8+ TAb-supp after ACT. Concurrent treatment with CNi (but not mTORi) reduced in vivo proliferation of CD8+ TAb-supp after ACT. The increase in quantity of splenic CD44+CXCR5+CD8+ T cells that occurs after ACT was reduced by concurrent treatment with CNi but not by concurrent treatment with mTORi (dose-dependent). Conclusions. Impaired efficacy of ACT by CNi is attributed to reduced persistence and/or expansion of CD8+ TAb-supp cells after ACT. In contrast, concurrent immunosuppression with mTORi preserves CD8+ TAb-supp cells quantity, in vivo proliferation, and in vivo cytotoxic effector function after ACT and enhances suppression of humoral alloimmunity and AMR.