Diffuse Extent of Peritubular Capillaritis in Late Antibody-mediated Rejection: Associations With Levels of Donor-specific Antibodies and Chronic Allograft Injury.

Background: Recently, diffuse peritubular capillaritis (ptc) has been suggested to independently predict chronic transplant injury and loss and while the ptc score is a diagnostic criterion for antibody-mediated rejection, the utility of diffuse ptc is under debate. Methods: We evaluated the diagnostic value of ptc characteristics in this cross-sectional study including 85 biopsies of patients with donor-specific antibodies (DSA). Biopsies were reevaluated for the extent (diffuse vs. focal), score and leukocytic composition in relation to DSA binding strength (MFI_max). Chronic allograft injury [transplant glomerulopathy (cg) or chronic lesion score (CLS)] were associated with ptc features. Results: Ptc was detected in 50% (76% mononuclear ptc). Ptc scores 1, 2, and 3 were present in 36%, 55% and 9 %, and focal or diffuse ptc in 36% or 64%. Diffuse ptc was associated with DSA MFI_max [median: 4407 vs. 2419 (focal ptc; p=0.04) or 1946 (no ptc; p=0.004)], cg [58% vs. no ptc 24% (p=0.02)] and higher CLS [mean: 6.81 vs. 4.67 (focal ptc, p=0.01) or 5.18 (no ptc, p=0.001)], respectively. The association of ptc score >=2 with cg was slightly better than with diffuse ptc. Diffuse ptc and ptc score >=2 remained independently related to cg after adjusting for DSA_MFI_max, C4d or previous rejection episodes, however lost their independent relation after adjusting for total microcirculation scores. Diffuse ptc was the only ptc characteristic independently related to CLS. Conclusion: Our results emphasize the clinical relevance of reporting diffuse ptc, which may relate to DSA binding strength and potentially to chronic graft injury. Copyright (C) 2017 Wolters Kluwer Health, Inc. All rights reserved.

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