OR15 Progressive chronic tissue injury without active pathological changes is the histological halmark of de novo class II DSA

Abstract

Aim There is no doubt that de novo anti-HLA Donor Specific Antibodies(dn-DSA) have deleterious effect on the kidney allograft. However, there is considerable controversy regarding the pattern of tissue injury generated by these antibodies. We set out to study the pattern of tissue injury of kidney biopsies procured in the early post-transplantation period (the first 5 years) in the for-the-cause biopsy practice setting at our institution. Methods All the cases with dn-DSA who had at least one kidney biopsy done in the first 5 years after kidney transplantation were included in the study. The type of dn-DSA (class I, class II or combined), presence/ type of rejection and the pattern of tissue injury based on Banff score and other histological findings were evaluated. Results Of the total of 36 cases fulfilling the criteria, 6(17%) had only class I, 21( 58%) had only class II and 9 ( 25%) had combined dn-DSA. There was no difference in clinical and laboratory parameters between the groups. Chronic histological changes either in tubulointerstitial compartment (ct and ci scores), vessels (cv score) or glomeruli (cg score) were significantly higher in cases with class II or mixed DSA than class I DSA. Mean ± SD for ct/ci, cv and cg in patients with class II or combined dn-DSA vs class I were 1.2 ± 1.0 vs 0.6 ± 0.5, 1.4 ± 1.1 vs 0.6 ± 0.8, 0.5 ± 0.8 vs nil, respectively. Interestingly, the recurrence of the original glomerulonephritis was only seen in association with class I DSA. Venulitis, not part of Banff score, was seen significantly more prevalent in class I DSA group (50%) compared to class II only or mixed group (10%). Conclusions Our study is limited by the low number of cases. However, some trends are readily appreciated. The tissue injury caused by class II dn-DSA is insidious and may be detected at late stages of rejection, even in early post-transplantation period. The clinical and laboratory parameters of rejection can be misleading in such cases and therefore, protocol biopsy practice is advisable.