Background: It is not uncommon to have biopsy specimens meeting Banff glomerulitis (g) plus peritubular capillaritis (ptc) and/or c4d scores that meet criteria for antibody mediated rejection (ABMR), but are found in the absence of anti-HLA DSA. Because our program has treated most of these HLA DSA negative (DSA -) patients with similar immunosuppressive protocols as those that were HLA DSA positive (DSA +), we report here on the clinical significance and outcomes of both groups.

Methods: We report our experience with kidney transplant recipients found to have DSA- ABMR between 03/01/2013 and 12/31/2016 and compared with DSA + ABMR. We included those with microvascular injury scores (MVI) ≥ 2 (regardless of c4d) and those with MVI ≥ 1 and c4d scores ≥ 2 on frozen section per Banff 2013 criteria.

Results: We identified 180 consecutive kidney biopsy with ABMR,25 (14%) DSA – and 155 (86%) DSA +. Mean age at the time of transplant was 41.2 ± 16.4 years. Mean post ABMR follow-up was 20.5 ± 13.6 months. There were no significant differences in baseline characteristics, induction immunosuppressive medications use or follow-up interval after ABMR between the two groups. At time of diagnosis, both groups had similar graft function. The DSA – group had higher MVI scores (3.0 ± 1.2 vs 2.4 ± 1.2, p=0.01) but lowerc4d scores (0.8 ± 1.2 vs 1.8 ± 1.3, p=<0.001). There was no statistically significant difference in the percent of patients in the two groups that received no treatment in response to the biopsy result: 12% in DSA – group vs 4% in DSA + group, p = 0.08. At last follow up, renal function was similar between the groups. There were a total of 71 (39%) graft failures, including 57 (32%) death-censored graft failures. There were 12 (out of 25, 48%) in the DSA – group and 59 (out of 155, 38%) graft failures in the DSA +, which was not statistically different. Similarly, there was no difference in uncensored or death-censored graft survival between the groups by Kaplan-Meier analysis.

Conclusion: Our findings suggest that despite treating most patients with HLA DSA – ABMR relatively aggressively, outcomes are similarly poor to those with DSA + ABMR. Future developments in tissue typing may allow greater sensitivity in detecting anti-HLA DSA and may allow the detection of pathogenic non-HLA antibodies. Until then, we suggest that patients meeting MVI and c4d criteria for ABMR, even in the absence of HLA DSA, may be considered as having ABMR.

CITATION INFORMATION: Parajuli S., Redfield R., Aziz F., Garg N., Mohamed M., Zhong W., Ellis T., Djamali A., Mandelbrot D. Clinical Significance of Microvascular Inflammation in the Absence of Anti-HLA DSA in Kidney Transplantation Am J Transplant. 2017;17 (suppl 3).

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