The impact of C 4d and microvascular inflammation before we knew them

It is important to identify prognostically important morphologic criteria in post‐transplant management to tailor therapy and improve outcomes. Therefore, using biopsies carried out for cause <1‐yr post‐transplant, from an era when C 4d staining and microvascular inflammation ( MVI ) were not clinically utilized, we studied the importance of C 4d and MVI on graft survival. Snap‐frozen first renal allograft biopsy specimens (done for cause) in the first post‐transplant year from 1996 to 2001 were stained/examined for C 4d, and pathology re‐examined by a separate blinded pathologist. Graft outcomes in patients with and without MVI and/or C 4d were compared. Of 128 patients, 39 (30.5%) biopsies were C 4d+ and 89 (69.5%) were C 4d−; 67 (52.3%) had no MVI ( MVI −) while 61 (47.7%) had glomerulitis, peritubular capillaritis, or both ( MVI +). There were no significant demographic differences between MVI + and MVI − patients. A greater proportion of C 4d+ biopsies was MVI + (67%) than MVI − (33%; p = 0.004). C 4d positivity had no impact on death‐censored graft survival ( DCGS ). In contrast DCGS was worse in MVI + than MVI − regardless of presence/absence of C 4d (p = 0.005). In biopsies for cause carried out <1‐yr post‐transplant, MVI is associated with decreased DCGS , independent of the presence of C 4d.