title: Mechanism of the combination immunosuppressive effects of rapamycin with either cyclosporine or tacrolimus.
abstract: BACKGROUND
  The combination of rapamycin with Cyclosporine has demonstrated beneficial effects in organ transplantation; however, the mechanism of this combination immunosuppression is not fully understood. The mechanism of action of cyclosporine and tacrolimus has been explained on the basis of their inhibition of interleukin-2 (IL-2), and induction of transforming growth factor-beta (TGF-beta). In this study, we explored the effects of rapamycin in combination with either tacrolimus or cyclosporine on lymphocyte proliferation, and expression of interleulin-2 (IL-2) and TGF-beta
  
  
  METHODS
  Peripheral blood mononuclear cells/lymphocytes were isolated from buffy coats obtained from blood center, and activated with phytohemagglutinin (PHA) in the presence or absence of rapamycin, cyclo sporine, and tacrolimus alone or in various combinations. The activation was quantified by 3H-thymidine uptake assay and using reverse transcriptase assisted polymerase chain reaction and ELISA, we studied the TGF-beta and IL-2 mRNA and protein expression, respectively.
  
  
  RESULTS
  In this study, we report that rapamycin in combination with either tacrolimus or cyclosporine significantly inhibited the lymphocyte proliferation, IL-2 expression, and induced TGF-beta, compared with these drugs alone. The levels of TGF-beta and IL-2 correlated positively and negatively, respectively, with inhibition of lymphocyte proliferation.
  
  
  CONCLUSIONS
  These novel findings provide the mechanism as well as the rationale to use these drugs in combination at subclinical dosages in organ transplantation.
authors.affiliation: The Cardiovascular Research Center, Medical College of Wisconsin, Milwaukee 53226, USA.
authors.forename: A K
authors.initials: AK
authors.lastname: Khanna
mesh_terms: D002478:Cells, Cultured; D016572:Cyclosporine / Q000494:pharmacology*; D004347:Drug Interactions; D005786:Gene Expression Regulation / Q000187:drug effects / Q000276:immunology; D006801:Humans; D007166:Immunosuppressive Agents / Q000494:pharmacology*; D007376:Interleukin-2 / Q000235:genetics; D008213:Lymphocyte Activation / Q000187:drug effects*; D012333:RNA, Messenger / Q000235:genetics; D012044:Regression Analysis; D020123:Sirolimus / Q000494:pharmacology*; D013154:Spleen / Q000276:immunology; D016559:Tacrolimus / Q000494:pharmacology*; D014158:Transcription, Genetic / Q000187:drug effects / Q000276:immunology; D016212:Transforming Growth Factor beta / Q000235:genetics
chemical_list: D007166:Immunosuppressive Agents; D007376:Interleukin-2; D012333:RNA, Messenger; D016212:Transforming Growth Factor beta; D016572:Cyclosporine; D020123:Sirolimus; D016559:Tacrolimus