Effect of human cytokines (IFN-gamma, TNF-alpha, IL-1 beta, IL-4) on porcine endothelial cells: induction of MHC and adhesion molecules and functional significance of these changes.

Previous studies using cultured human endothelial cells have demonstrated the role of inflammatory cytokines [interferon-gamma (IFN-gamma), tumour necrosis factor-gamma (TNF-alpha), interleukin-1 beta (IL-1 beta) and IL-4] in the regulation of major histocompatibility complex (MHC) and adhesion molecule expression. These cytokines are therefore implicated in the amplification of allograft, and more recently xenograft, rejection. In view of the likely event of grafted porcine tissues being exposed to human cytokines, we have investigated the effect of IFN-gamma, TNF-alpha, IL-1 beta, IL-4 and recombinant porcine IFN-gamma (rpoIFN-gamma) on cultured porcine aortic endothelial cells (PAEC) with respect to induction/up-regulation of porcine MHC and adhesion molecules and B7 receptors. Expression was detected using monoclonal antibodies (mAb) against porcine ligands and human CTLA-4-immunoglobulin; binding was analysed by flow microfluorimetry. TNF-alpha but not the other human cytokines unregulated swine leucocyte antigens (SLA) class I, class II and B7 receptor expression and induced vascular cell adhesion molecule (VCAM) and E-selectin expression. Porcine IFN-gamma also up-regulated SLA class I and class II, the ligand for CTLA-4-immunoglobulin and VCAM expression; the magnitude and kinetics of this response differed to that produced by recombinant human TNF-alpha (rhTNF-alpha). The ability of untreated, rpoIFN-gamma- and rhTNF-alpha-treated PAEC to stimulate CD4+ T cell was compared. CD4+ T-cell proliferation and IL-2 production were significantly enhanced by rhTNF-alpha and rpoIFN-gamma, rpoIFN-gamma being more effective than rhTNF-alpha. Use of blocking antibodies and CTLA-4-immunoglobulin demonstrated that the enhanced proliferative response, but not apparently IL-2 production, was dependent on cytokine-mediated up-regulation of SLA class II and B7 receptors. In conclusion, human TNF-alpha acts as a proinflammatory cytokine on PAEC and is likely to enhance the cellular response to xenogeneic organs in vivo.