title: Evidence that increases in lymphocyte tyrosine phosphorylation precede cardiac allograft rejection. Effects of cyclosporine and potential use in clinical management.
abstract: Tyrosine phosphorylation is an early, critical event in lymphocyte signal transduction. We measured tyrosine phosphorylation in a porcine experimental transplant model to evaluate its utility in monitoring the allograft immune response. Using flow cytometry, we demonstrate a biphasic increase in phosphotyrosine (ptyr) levels in peripheral blood mononuclear cells (PBMC), and that increases are detectable as early as 1 day posttransplantation in untreated transplanted animals (n = 4). This biphasic response is likely result from the sequestration of ptyr+ cells from the periphery into the graft as graft-infiltrating lymphocytic cells show increased ptyr levels. This suggests possible lymphocyte trafficking between the peripheral compartment and the allograft. A 5-day course of treatment with cyclosporine (CsA) at 20 mg/kg/day (n = 4), but not at 10 mg/kg/day (n = 4), prevents graft rejection in this allograft model. Strikingly, treatment with 20 mg/kg/day CsA, but not with 10 mg/kg/day, suppressed increases in ptyr levels in both PBMC and graft-infiltrating cells. Increases in ptyr levels in PBMC are detectable 2-5 days before histologic and electrocardiographic signs of graft rejection, suggesting a potential diagnostic utility for measuring tyrosine phosphorylation in monitoring and managing transplant rejection.
authors.affiliation: Department of Pharmacology, University of Toronto, Canada.
authors.forename: P W
authors.initials: PW
authors.lastname: Tsao
authors.forename: G B
authors.initials: GB
authors.lastname: Mills
authors.forename: R J
authors.initials: RJ
authors.lastname: Diaz
authors.forename: I C
authors.initials: IC
authors.lastname: Radde
authors.forename: D
authors.initials: D
authors.lastname: Parkinson
authors.forename: J
authors.initials: J
authors.lastname: Waddell
authors.forename: G J
authors.initials: GJ
authors.lastname: Wilson
authors.forename: J G
authors.initials: JG
authors.lastname: Coles
mesh_terms: D000818:Animals; D015415:Biomarkers; D016572:Cyclosporine / Q000627:therapeutic use*; D005434:Flow Cytometry; D006084:Graft Rejection / Q000175:diagnosis* / Q000517:prevention & control; D016027:Heart Transplantation; D007124:Immunoenzyme Techniques; D016130:Immunophenotyping; D008214:Lymphocytes / Q000378:metabolism*; D009206:Myocardium / Q000378:metabolism; D010766:Phosphorylation; D019000:Phosphotyrosine; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D015398:Signal Transduction; D013552:Swine; D014184:Transplantation, Homologous; D014443:Tyrosine / Q000031:analogs & derivatives / Q000032:analysis / Q000378:metabolism*
chemical_list: D015415:Biomarkers; D019000:Phosphotyrosine; D014443:Tyrosine; D016572:Cyclosporine