Vascularized Composite Allograft Rejection Is Delayed by Intrajejunal Treatment with Donor Splenocytes without Concomitant Immunosuppressants

Background. Mucosal or oral tolerance, an established method for inducing low-risk antigen-specific hyporesponsiveness, has not been investigated in vascularized composite allograft (VCA) research. We studied its effects on recipient immune responses and VCA rejection. Methods. Lewis rats (n=12; TREATED) received seven daily intrajejunal treatments of 5×107 splenocytes from semiallogeneic Lewis-Brown-Norway rats (LBN) or vehicle (n=11; SHAM). Recipients’ immune responses were assessed by mixed lymphocyte reaction (MLR) against donor antigen and controls. Other Lewis (n=8; TREATED/VCA) received LBN hindlimb VCA and daily intrajejunal treatments of 5×107 LBN splenocytes, or LBN VCA without treatment (n=5; SHAM/VCA), until VCAs rejected. Recipients’ immune responses were characterised and VCAs biopsied for histopathology. Immunosuppressants were not used. Results. LBN-specific hyporesponsiveness was induced only in treated Lewis recipients. Treatment significantly reduced MLR alloreactivity, significantly reduced VCA rejection on histopathology, and significantly delayed clinical VCA rejection (P