Anti-TNF antibody modulates cytokine and MHC expression in cardiac allografts.
Tumor necrosis factor-alpha (TNF) is a multifunctional cytokine evoked in response to alloantigen stimulation and may be involved in lymphocyte activation, adhesion molecule expression, and regulation of MHC class II antigens. Anti-TNF treatment prolongs cardiac allograft survival. We investigated the role of anti-TNF in the regulation of MHC class II antigens and cytokine mRNA expression of TNF, interferon-gamma (IFN), IL-2, IL-4, and IL-10 in cardiac allografts to elucidate its immunological mechanism. These in vivo studies were conducted using a rat MHC mismatch Brown-Norway to Lewis (BN to LEW) heterotopic cardiac transplant model. In control untreated rats, allografts were rejected at 6.8 +/- 0.6 days. Allograft survival was significantly prolonged to 12.7 +/- 1.4 days with anti-TNF treatment. MHC class II expression, analyzed by indirect immunofluorescence cytometry, demonstrated that MHC class II-positive cells increased by 25% in spleens of untreated allografted rats compared to naive rats, while anti-TNF-treated allografted rats had a similar percentage of MHC II cells as naives. Further, naive, untransplanted rats and both anti-TNF and untreated, transplanted rats had heart and spleens harvested on Day 5 post-transplant. Cytokine mRNA expression was determined by semiquantitative RT-PCR. In heart and spleen cells from naives, TNF mRNA expression was undetectable or very weak. However, in rejecting allografts and spleen cells from untreated recipients, TNF expression was remarkably increased, while anti-TNF attenuated this TNF expression in both heart graft and spleen cells. Furthermore, IL-2, IL-10, and IFN expression were absent in naive hearts. However, in untreated allografts IL-2, IL-10, and IFN were strongly expressed, which was markedly decreased after anti-TNF treatment. Finally, IL-4 expression was found equally in naive hearts, untreated allografts, and anti-TNF-treated allografts. These results suggest that anti-TNF antibody treatment may not only neutralize TNF activity but also play a role in altering cytokine mRNA expression and MHC class II expression.