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 although 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 (mean fluorescence intensity [MFI]_max). Chronic allograft injury (transplant chronic glomerulopathy [cg] or chronic lesion score CLS]) were associated with ptc features.

RESULTS: Peritubular capillaritis was detected in 50% (76% mononuclear ptc). Peritubular capillaritis 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 of 2 or greater with cg was slightly better than with diffuse ptc. Diffuse ptc and ptc score of 2 or greater 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.

CONCLUSIONS: Our results emphasize the clinical relevance of reporting diffuse ptc, which may relate to DSA binding strength and potentially to chronic graft injury.