Cultured mouse keratinocyte allografts prime for accelerated second set rejection and enhanced cytotoxic lymphocyte response

It has been reported that cultured keratinocyte (CK) allografts are not rejected in mice, unlike in other species. Several reports have suggested that mouse CK allografts are incapable of stimulating a primary al-loresponse, including sensitization of recipients to al-loantigens. In this study, we investigated the immuno-genicity of mouse CK allografts in vivo by determining whether CK allografts primed for a second set rejection response. First, we grafted mice with either CK allografts, CK autografts, full-thickness (FT) allografts, or no graft at all. We then regrafted mice 4 weeks later with a tail skin allograft. Mice grafted with CK allografts rejected second allografts as rapidly and as vigorously as mice grafted with FT flank allografts. Next, we tested whether CK allograft primed recipients for enhanced CTL responses. We found that mice grafted with CK allografts generated a significantly enhanced CTL alloreactive response after in vitro stimulation. The response was similar to that of mice grafted with FT skin allografts. With evidence that CK allografts primed, we biopsied wounds immediately after CK allografting and, using Western immunoblot-ting, found that CK allografts had substantial expression of MHC class II antigens in vivo. We conclude from the results of our studies that mouse CK allografts unequivocally prime recipients to alloanti-gens in vivo and suggest that a possible mechanism for alloantigen priming may be CK allograft expression of MHC class II antigens.