Reduced CD40L expression on ex vivo activated CD4+T-lymphocytes from patients with excellent renal allograft function measured with a rapid whole blood flow cytometry procedure

Background: The CD40-CD40L (CD154) costimulatory pathway plays a
critical role in the pathogenesis of kidney allograft rejection. In
renal transplant biopsies, CD4+ CD40L+ graft-infiltrating cells
were detected during chronic rejection in contrast to acute
rejection episodes. Using a rapid noninvasive FACS procedure, we
were able to demonstrate CD40L upregulation in peripheral blood of
patients with chronic renal allograft dysfunction. Materials and
Methods: Whole blood from recipients of renal allografts was
stimulated with PMA and ion-omycin and measured by flow cytometry.
Patients were assigned to three groups based on transplant
function. Group 1: 26 patients with excellent renal transplant
function; group 2: 28 patients with impaired transplant function;
group 3: 14 patients with chronic allograft dysfunction and group
4: 8 healthy controls. Results: The median percentage +/-SEM of
CD4+/ CD40L+ cells stimulated ex vivo at 10 ng/ml PMA was as
follows: group 1: 28.3 +/- 4.1%; group 2: 18.4 +/- 2.4%; group 3:
50.1 +/- 5.0% and group 4: 40.4 +/- 3.4%. Subdivisions of groups 2
and 3 resulted in different CD40L expression patterns. Patients
with increased serum creatinine since the initial phase after
transplantation ( groups 2a and 3a) revealed a higher percentage of
CD4+ CD40L+ cells than patients showing a gradual increase over
time ( groups 2b and 3b). Consequently, patients of group 3a
exhibited a significantly reduced transplant function compared with
those of group 3b. Conclusion: After PMA + ionomycin stimulation,
patients with excellent kidney graft function displayed
significantly reduced expression of CD40L surface molecules on CD4+
cells early after transplantation. Those with a chronic dysfunction
of the renal graft showed significantly more CD4+ cells expressing
CD40L compared to the other transplanted groups. These results
demonstrate that the percentage of CD4+ CD40L+ cells stimulated ex
vivo in peripheral blood may be a valuable marker for chronic
allograft nephropathy. Copyright (C) 2004 S. Karger AG, Basel.