Focal peritubular capillary C4d deposition in acute rejection

Background. Diffuse peritubular capillary (PTC) C4d deposition has been shown to be associated with relatively poor graft outcome. The significance of focal PTC C4d staining in the early post-transplant period is uncertain. Methods. Sixty-five biopsies from 53 patients with acute rejection were graded (Banff '97 criteria), stained for C4d, monocytes and T cells, and divided into three groups according to PTC C4d: (i) focal C4d (F) (14 biopsies, 14 patients), (ii) diffuse C4d (D) (23 biopsies, 15 patients) and (iii) no C4d (N) (28 biopsies, 24 patients). The three groups were compared with respect to a variety of biopsy and clinical parameters including outcome. Results. The incidence of transplant glomerulitis and glomerular monocyte infiltration were significantly greater in F (64% and 2.0 +/- 2.0) and D (57% and 3.4 +/- 2.0) than in N (11% and 0.2 +/- 0.2). A significantly higher proportion of F (93%) demonstrated acute cellular rejection (Banff '97 grade >= 1A) than did D (35%). The F and D groups included significantly more females (50 and 67%, respectively) than did N (21%). The percentage of patients with a second or third transplant was higher in F (29%) and D (40%) than in N (8%) (P = 0.0589). The proportion of patients with glomerular filtration rate < 30 ml/min at 12, 24 and 48 months was higher in the D and F groups than in the N, and there was a statistically significant increasing trend in odds of this outcome occurring at 48 months across the three groups (D > F > N group) (P = 0.0416). Conclusion. The results suggest that the biopsy findings and clinical course in patients with focal PTC C4d staining are similar to those associated with diffuse C4d.