Clinical outcome of kidney grafts that are affected by the complex syn
drome of 'early graft dysfunction' is uncertain and rather unpredictab
le. In this study, an individual prognosis for dysfunctioning allograf
ts (N = 93) is attempted by the immunohistological assessment of vascu
lar classical complement activation in graft biopsies. Thus, capillary
deposition of complement fragment C4d was observed in the majority (N
= 51) of early dysfunctioning grafts. In 43 biopsies, abundant deposi
tion of fragment C4d was present in all capillaries, whereas in eight
specimens a segmental distribution of capillary C4d was observed. In 4
2 grafts with early dysfunction no capillary C4d was detectable. Eight
een subsequent graft losses within one year (16 early losses) were rec
orded in the subgroup with C4d in all capillaries, and three early los
ses in the group with segmentally distributed C4d. Only four graft los
ses (3 early losses) were recorded in the C4d-negative group (P = 0.00
27; Pearson's chi square test). The resulting one-year graft survival
rates (72% for the study group) differed markedly between the subgroup
s. Grafts with generalized or segmental capillary deposition of C4d ha
d 57% and 63% survival, respectively, contrasted by 90% survival in th
e C4d-negative group. It is of note, however, that also three of the f
our grafts that were finally lost within the C4d-negative group, showe
d distinct capillary deposition of C4d in second biopsies. Vascular de
position of complement fragment C4d therefore represents a clinically
relevant factor that contributes to early graft dysfunction. Its asses
sment is helpful for an individual graft prognosis.