Moderate additive immunosuppressive effect of thalidomide combined with cyclosporin A in rat cardiac transplantation.

Thalidomide is an immunomodulating agent shown to prolong graft survival in experimental skin, renal, cardiac and bone marrow transplantation. The main purpose of the present study was to investigate the possible additive effect of combining thalidomide with cyclosporin A (CyA). Members of our group have previously created a basis for such studies by demonstrating the ability of Linomide to abolish the effect of CyA. The additional effect of combined treatment with a second drug is thereby more readily evaluated, compared with using subtherapeutic dose levels to induce early rejection. Cardiac grafting was performed in three rat strain combinations (BN to WF, DA to Lew, and BN to Lew). Rats were given no treatment, or thalidomide, CyA and/or Linomide in single, double or triple drug therapy. Except for a consistent beneficial effect of CyA as single drug treatment, graft survival varied depending on the rat strain combination used. In the DA to Lew combination, the expected effects of Linomide were seen, and thalidomide was shown to prolong graft survival significantly (P = 0.004) when added to CyA and Linomide. However, there was no effect of thalidomide when given alone. In WF recipients of BN hearts, thalidomide tended to prolong graft survival (P = 0.07), and surprisingly Linomide manifested a marked immunosuppressive effect (P = 0.0002) and did not counteract the effect of CyA. When transplanting BN grafts to Lew recipients, Linomide reduced significantly but did not abolish completely the effect of CyA. Neither Linomide nor thalidomide had any beneficial impact on graft survival on their own. To sum up, thalidomide was shown to have a minimal or moderate immunosuppressive effect additive to that of CyA. The effects of the two immunomodulating drugs, thalidomide and Linomide, varied depending on the rat strain combination used, and were similar with respect to prolongation of graft survival when used as single drug treatment in BN to WF grafting, a fact which may indicate them to have a similar mechanism of action, both having been shown to exert similar effects on levels of tumour necrosis factor alpha.