Development of a novel transgenic mouse for the study of interactions between CD4 and CD8 T cells during graft rejection.

The goal of this study was the development of a system in which the cooperative interactions between CD4 and CD8 T cells specific for defined peptides from a single minor histocompatibility antigen could be studied. A transgenic mouse strain that expresses chicken ovalbumin (Act-mOVA) on the surface of all cells in the body was produced as a source of tissues containing such an antigen. Skin grafts from Act-mOVA donors were rapidly and completely rejected by wild-type recipients, but only when both CD4 and CD8 T cells were present. CD4 T cells by themselves caused an incomplete form of rejection characterized by rapid but partial contraction of Act-mOVA grafts. CD8 T cells alone caused complete rejection of Act-mOVA skin grafts but only after a long delay. Adoptively transferred ovalbumin-specific TCR-transgenic CD4 and CD8 T cells were stimulated by Act-mOVA graft antigens and CD8 T-cell accumulation in the grafts was enhanced by specific CD4 T cells. These findings, together with the fact that the ligand for ovalbumin peptide-specific CD8 T cells can be detected in Act-mOVA tissues with an MHC-restricted antibody, make this an ideal system for the study of cooperation between CD4 and CD8 T cells.