Tracking the direct alloimmune response in vivo with a new CD4+ T cell receptor transgenic mouse model

Abstract

Abstract Introduction: T cell receptor transgenic (TCR-tg) mice have been critical to the study of T cell responses in vivo. The alloimmune CD8+ TCR-tg, 2C, has revealed important insights into the responses of the CD8+ T cell in transplant rejection. We thus developed a CD4+ TCR-tg mouse with strain specificity identical to the 2C TCR-tg to study the CD4+ T cell in allograft rejection. Methods: Balb/c dendritic cells were used to immunize a B6 recipient from which alloreactive CD4+ T cells were isolated. The alpha and beta chains of the TCR were then reverse transcribed from mRNA and cloned into expression vectors behind the human CD2 and the murine CD4 promoters, respectively. These vectors were injected together into embryos and offspring were screened for the expression of the transgenic TCR. Results: A founder (4C) expressing the transgenic TCR on > 99% of peripheral CD4+ T cells was identified. Expression was shown by RT-PCR and flow cytometry. TCR function was demonstrated by T cell proliferation in response to Balb/c antigen both in vitro and in vivo following adoptive transfer. Antibody blockade experiments show the TCR reacts to antigen in the context of the MHC class II molecule I-Ad. We find the 4C TCR-tg to reject Balb/c skin grafts in 10–12 days. Conclusions: We have developed a CD4+ TCR-tg mouse for the study of alloimmunity. Adoptive transfer experiments combining the 2C and 4C T cells will provide a novel means of observing the cooperativity of these T cells subsets during transplant rejection and tolerance.