INHIBITION OF ANTIBODY-DEPENDENT CELL-MEDIATED LYSIS OF PORCINE AORTIC ENDOTHELIAL CELLS (PAECS) BY PREVENTING FC-FcR BINDING.

Abstract

509 While xenograft loss due to HAR is prevented by effective complement inhibition, graft loss due to acute vascular xenograft rejection (AVXR) is not, and therefore other potential mechanisms for AVXR must be evaluated. We hypothesize that persistent endothelial deposition of xenoantibodies may facilitate AVXR by enhancing the binding of cytotoxic Fc receptor (FcR) bearing cells to PAECs through Fc-FcR interactions. The purpose of this study was to determine if preventing Fc-FcR interactions could inhibit the overall lysis of PAECs caused by human peripheral blood leukocytes (hPBLs). hPBL effector cells were preincubated with mouse monoclonal anti-human FcR antibodies (anti-CD64, anti-CD32, and anti-CD16) prior to their incubation with Cr-labelled PAEC target cells that had been preincubated with heat-inactivated pooled human AB serum (HIPHS). Using this method, with an Effector:Target (E:T) ratio of 20:1, antibody-dependent cell-mediated PAEC lysis was reduced from 19.7 ± 4.5 % to 12.8 ± 2.2 % (p=0.003). In additional studies using a different approach, hPBLs were incubated with Cr-labelled PAECs which had been preincubated with HIPHS after initial precoating with avian anti-αGal IgY antibodies. Avian IgY antibodies were used because of their high anti-αGal content and their inability to bind human complement or human Fc receptors. The results obtained were: (Table)TableThese results indicate that ADCC can be inhibited by preventing Fc-FcR binding between FcR bearing cells and endothelial-bound xenoantibody. The development of strategies which can prevent these interactions in vivo may help to prevent AVXR.