CLINICAL VALUE OF POST-TRANSPLANT FLOW CYTOMETRIC CROSSMATCH IN RENAL
ALLOGRAFT.
D Adorno*, A Piazza*, E Poggi°, O Buonomo°, M Valeri°,
N Torlone°, PI Monaco* , C Cortini° and CU Casciani°. *CNR
Inst. Tissue Typing - Unit of Rome, ° Department of Surgery-University
"Tor Vergata", Rome , Italy.
The presence of preformed anti-donor antibodies (ADA)
is detrimental for renal transplant outcome, on the contrary the relevance
of such ADA produced after transplant is not completely clear. Moreover
it is well accepted that the appearance of early acute rejection (ARj)
is associated with poor long-term survival. The aim of this study was to
evaluate the ability of flow cytometric crossmatch (FCXM), performed routinely
after renal transplant, both in monitoring donor-specific immune response
and in predicting kidney graft outcome. 66 patients who underwent cadaveric-donor
renal transplant were monitored using FCXM (triple staining method: anti-CD3
PerCP and anti-CD20 Pe to identify T and B donor cells, anti-human IgG
or IgM to identify ADA) during the first three months after transplant.
Donor spleen cells were stored in liquid nitrogen until use. Patients sera
were taken before and after transplant on days 7, 14, 30, 60, 90 and when
clinical symptoms were suspicious of ARj. ARj episodes were diagnosed on
the basis of renal biopsy; 21 of the 66 patients experienced one or more
ARj episodes within the third month after transplantation. In 15 of the
66 (22.7%) patients we found a FCXM positivity at least once. Among the
FCXM-positive patients 12 (80%) experienced ARj; on the contrary only 5
of the 51 FCXM-negative patients had ARj (p<0.00001). Studing the onset
of FCXM positivity we found that FCXM analysis revealed in all but one
FCXM-positive patients the presence of ADA from seven to one days before
the clinical appearance of rejection. With regard to graft outcome at one
year post transplantation we observed that all 5 patients who lost graft
were both FCXM and ARj positive (5/12 = 41.7%); moreover no graft was lost
in the patients who were only FCXM-positive or only ARj positive (p=0.001).
In our experience the FCXM seems to be a noninvasive and sensitive approch
for estimating post-transplant "donor specific" humoral immunity and also
for predicting long term graft outcome