Clinical Significance of Microvascular Inflammation in the Absence of Anti-HLA DSA in Kidney Transplantation.

BACKGROUND: Limited information exists about outcomes of HLA DSA negative (DSA-) microvascular inflammation (MVI).

METHODS: We report our experience with 25 DSA- patients with MVI compared to 155 DSA+ patients who met Banff 2013 criteria for ABMR. We also compared outcomes to 228 DSA+ patients whose biopsies were negative for rejection, and served as a negative control.

RESULTS: There were no significant differences in the baseline characteristics between the DSA- MVI and DSA+ ABMR groups. At the time of diagnosis, both groups had similar graft function. The DSA- group had higher MVI scores but lower C4d scores. At last follow up, renal function was similar between the groups. There were 12(48%) graft failures in the DSA- group and 59 (38%) graft failures in the DSA+ group, which was not statistically different. Similar results were found after matching for the MVI scores, C4d, and treatment between two groups. We also found similar outcomes between DSA- and DSA+ patients when only including those who would have met Banff 2017 criteria for ABMR. In univariate Cox regression analyses, eGFR at time of biopsy, glomerulitis, rituximab, diabetes, v score, cg, cv, ct, and ci scores were associated with graft failure. In multivariate analysis, only eGFR was protective. Both groups had significantly worse outcomes than the DSA+ negative controls without ABMR.

CONCLUSIONS: Our findings suggest that outcomes and response to treatment with HLA DSA- MVI patients are similarly poor to those with DSA+ MVI patients, supporting a critical role for MVI in the diagnosis of ABMR.