Background: Experimental studies have demonstrated that the intensity of alloreactivity against a transplanted organ results from an interaction of positive (CD40/CD40L and B.7/CD28) and inhibitory (B.7/CTLA-4) signals between antigen-presenting cells (APCs) and T lymphocytes.
Methods: We examined the CD40L, CD28, and both surface (s) and intracellular (i) CTLA-4 expressions on freshly drawn and anti-CD3+rIL-2-stimulated peripheral blood CD4+ T cells in groups of kidney transplant recipients in relation to distinct clinical course using the tri-color immunofluorescence method.
Results: The median proportions of freshly isolated CD3+/CD4+/CTLA-4+ and CD3+/CD4+/CD40L+ cells in all groups of graft recipients were higher than in control subjects. In patients with stable graft function (SGF), non-significantly higher sCTLA-4, significantly higher iCTLA-4 expression, and significantly lower CD40L expression on freshly drawn CD4+ T cells compared with recipients with chronic allograft nephropathy (CAN) were found. Moreover, CD4+ T cells from SGF patients showed a higher potential to express sCTLA-4 and CD40L molecules and to down-regulate the CD28 molecule in response to ex vivo stimulation than those from patients with CAN. In patients without acute graft rejection (NAGR), a markedly higher proportion of freshly drawn CD3+/CD4+/iCTLA-4+ cells compared with patients with acute graft rejection (AGR) and an up-regulation of the median percentage of CD3+/CD4+/CD40L+ cells after ex vivo stimulation was found.
Conclusions: In patients with SGF, peripheral blood CD4+ T cells exhibited a higher potential to express surface CTLA-4 and CD40L and to down-regulate CD28 costimulatory molecules in response to ex vivo stimulation, indicating a relationship between the expression patterns of both costimulatory and inhibitory molecules in CD4+ T cells and clinical course after renal transplantation.