Blood levels of TGF beta(1) in liver transplant recipients receiving either tacrolimus or micro-emulsified cyclosporine

Background. Transforming growth factor beta-1 (TGF beta(1)) is pro-fibrotic in addition to being a potent immunosuppressive cytokine. Cyclosporine (cy closporin A[CsA]) has been found to increase circulating TGF beta(1) levels in patients (1, 2). To determine whether tacrolimus (FK506) similarly incr eases TGF beta(1), we have measured TGF beta levels in blood samples from l iver graft recipients who were of known TGF beta 1-responder status. Methods. Sequential serum and plasma samples were obtained from liver trans plant recipients in the UK trial of tacrolimus versus microemulsified CsA, with a follow up period of between 50 and 265 days. Twelve patients receive d CsA and 13 received tacrolimus. Active and total TGF beta(1) protein were measured and plasma beta thromboglobulin (beta TG) levels were used as an indirect indication of platelet-derived TGF beta contamination of samples. Results. We found no correlation between trough drug levels and active TGP beta(1) levels in serum of either set of patients. Plasma beta thromboglobu lin was detected in platelet-depleted plasma samples, indicative of platele t damage before plasma separation. Conclusion. Neither CsA nor tacrolimus induced active TGF beta(1) blood lev els in liver transplant recipients during a follow up period of less than o r equal to 265 days.