Rats injected with syngenic rat apoptotic neutrophils develop antineutrophil cytoplasmic antibodies

Antineutrophil cytoplasmic antibodies (ANCA) are present in sera from patients with various forms of vasculitis-associated glomerulonephritis. Because autoantibodies may be directed against antigens presented by apoptotic cells, generation of ANCA using apoptotic neutrophils (PMN) in syngenic Brown Norway (BN) rats was attempted. These rats are T-helper type 2-prone animals, already used successfully in other ANCA-positive animal models. BN rats received repeated injections of buffer or of nonapoptotic or apoptotic PMN aged in cultures, in the footpad and once intravenously. Four of five rats that received injections of PMN aged for 48 h developed ANCA, which cross-reacted with human leukocyte elastase in three cases. None of the rats that received injections of freshly isolated neutrophils developed ANCA. One rat that received buffer injection and that exhibited chronic skin infection developed delayed ANCA. None of the rats showed signs of disease: no weight loss and no proteinuria. Then a subnephritogenic dose of antibody directed against rat glomerular basement membrane was injected. Rats then were killed, and different organs were frozen and studied. No significant lesions were found in kidneys or lungs. It is concluded that injections of apoptotic but not freshly isolated PMN can generate ANCA in BN rats. Additional studies are needed to elucidate the immunization mechanism and the ability of these autoantibodies to initiate vasculitis in these experimental animals.