A sensitive screening method of detecting anti-granulocyte antibodies employing radiolabeled staphylococcal protein A

We describe an improved method of detecting anti-granulocyte antibodies utilizing radiolabeled staphylococcal protein A (SPA). The results of this SPA assay were compared to data obtained with leukoagglutination tests and granulocyte indirect immunofluorescence techniques. We have shown that the SPA assay is highly sensitive and reproducible. In addition, absorption studies confirmed that the assay is specific for granulocytes. The SPA assay is performed in microtiter plates, and requires significantly fewer granulocytes and less test sera than previously described techniques. Also, we have shown that granulocytes prepared for this assay can be separated and stored for up to 48 h. Therefore, the SPA assay described herein is particularly useful for screening of sera and is one of the most sensitive assays available for detecting anti-granulocyte antibodies.