Prolongation of islet allograft survival with an antibody to vascular cell adhesion molecule 1

Background. The purpose of this study was to determine whether an antibody to vascular cell adhesion molecule 1 (VCAM1) prolongs the survival of neovascularized pancreatic islet allografts. Methods. We treated CBA (H-2^k) recipients of BALB/c (H-2^d) islet allografts with anti-VCAM1 antibody (400 μg/day for 20 days). Sensitized recipients of islet grafts also were treated with anti-VCAM1. To study mechanism we performed mixed lymphocyte reactions (MLRs) with anti-VCAM1 and studied the graft infiltrate in treated recipients. Results. Anti-VCAM1-trented CBA recipients showed prolonged graft survival with indefinite survival in five of nine cases. Anti-VCAM1 prevented proliferation in an MLR but not when added 36 hours after the beginning of the MLR. Anti-VCAM1 did not prolong allograft survival in sensitized recipients and did not prevent lymphocytic infiltration of the graft at 7 days. Conclusions. Anti-VCAM1 prolongs allograft survival in neovascularized islets in which the donor vascular endothelium plays little or no role in immunogenicity. VCAM1 appears to be important in the afferent phase (lymphocyte activation) of the allograft response. Once activated, either late in an MLR or in sensitized recipients, lymphocytes are not dependent on VCAM1 for function. Finally, anti-VCAM1 does not appear to affect the homing of lymphocytes to the allograft.