CD4 and vascular disorder: Instead, a further model of chronic alloantibody-mediated allograft vasculopathy was developed in which B6 Tcrbd−/− recipients of BALB/c heart allografts are reconstituted at transplantation with B6 TCR75 CD4 T cells but at limiting numbers (103 per mouse), such that rejection occurs slowly and is mediated by anti-H-2Kd GC alloantibody responses, with help provided by differentiation of the transferred TCR75 T cells to follicular helper T cells (Figure 6A).