C4d deposition is associated with immune cells infiltrating in kidney allograft glomerulitis and peritubular capillaritis

Objective: The aim of our study was to determine the amount and composition of immune cells within glomeruli and PTCs and its relationship with C4d deposition. Materials and methods: Immunohistochemistry staining for C4d, CD3, CD68, granzyme B and Foxp3 was used for phenotyping and enumerating immune cells within intracapillaries. Results: C4d staining was present in 26 biopsy specimens (C4d(+)) and negative in 25 specimens (C4d(-)). The total number of infiltrating cells in glomerulus and PTC in C4d(+) was significantly higher than in C4d(-). Although the C4d(+) showed a significantly higher mean number of macrophages per glomerulus and PTC than in C4d(-) group, the C4d(-) showed a higher mean number of T cells per glomerulus and PTC than in C4d(+). Comparing cell counts in diffuse C4d(+) and focal C4d(+) groups, a significant difference of absolute numbers of intracapillary cells could be observed in glomeruli and PTCs. The mean number of macrophages per glomerulus and PTC in diffuse C4d(+) was greater than that of the focal C4d(+), while mean T cells per glomerulus and PTC were less in cases of diffuse C4d(+) than in focal C4d(+). The differences, however, did not achieve statistical significance. Not only glomerular T cells but also PTCs are granzyme B positive T cells totally. Conclusion: The total number of infiltrating cells in glomeruli and PTC has association with PTC C4d deposition; the infiltrating cells were predominantly macrophages in C4d(+), especially in diffuse C4d(+), whereas the infiltrating cells were predominantly T cells in C4d(-). Glomerular and PTC T cells were cytotoxic phenotype completely.