Mechanisms and kinetics for platelet and neutrophil localization in immune complex nephritis

We have previously reported that both neutrophils (PMNs) and platelets mediate proteinuria in a model of subendothelial immune complex (IC) nephritis (GN) in the rat. In order to understand the interaction of PMNs and platelets in this model, we quantitated the uptake of 111In-labelled platelets in glomeruli and correlated this with the number of PMNs observed histologically at 10 and 30 minutes, 1, 4 and 24 hours following induction of GN. Platelet accumulation was biphasic with a major peak at 10 minutes and a minor peak at four hours. Early platelet accumulation was complement dependent, and PMN-independent. PMN accumulation occurred after the initial platelet influx, peaking at one and four hours, was complement dependent, but was not affected by platelet depletion. Complement depletion significantly reduced proteinuria. This is the first documentation that platelet accumulation in glomeruli in IC GN is complement dependent. In addition, the enhancement of PMN-mediated injury by the platelet in this model does not involve effects of platelets on PMN localization, thus implying a functional interaction between these cells within the glomerulus.