Search

Thrombotic microangiopathy (TMA) is one of the hallmark vascular lesions of antiphospholipid syndrome nephropathy (APSN). These lesions are at high risk of recurrence after kidney transplantation. The complement pathway is thought to be active in this process. We used eculizumab to treat three consecutive kidney transplant recipients with posttransplant TMA due to APSN recurrence that was resistant to plasmapheresis and explored the complement deposition and apoptotic and vascular cell markers on the sequential transplant biopsies. Treatment with eculizumab resulted in a rapid and dramatic improvement of the graft function in all three patients and in improvement of the TMA lesions within the graft. None of these patients had TMA flares after eculizumab was withdrawn. At the time of TMA diagnosis, immunofluorescence studies revealed intense C5b-9 and C4d depositions at the endothelial cell surface of the injured vessels. Moreover, C5b-9 colocalized with vessels exhibiting a high rate of apoptotic cells. Examination of sequential biopsies during eculizumab therapy showed that TMA lesions, C4d and apoptotic markers were rapidly cleared but the C5b-9 deposits persisted for several months as a footprint of the TMA. Finally, we noticed that complement inhibition did not prevent the development of the chronic vascular changes associated with APSN. Eculizumab seems to be an efficient method for treating severe forms of posttransplant TMA due to APSN recurrence. Terminal complement inhibition does not prevent the development of chronic APSN.

Microchimerism after allogeneic organ transplantation may be a mechanism for induction of donor-specific graft acceptance. However, the frequency of chimerism and its relevance in long-term tolerance are uncertain. We studied 15 long-surviving (more than 20 years) cadaveric-kidney transplant recipients for the systemic presence of donor alleles with allele-specific genomic amplification of DRB1 and H-Y loci. Microchimerism was observed in 1 case in peripheral blood and in 4 cases in skin. Chimerism and number of HLA alleles shared by donor and recipient were not correlated. This low frequency of microchimerism in long-term kidney allograft recipients raises doubts about a major participation of chimerism in donor-specific tolerance.