Human IgG antigranulocyte antibodies: comparison of detection by quantitative antiglobulin consumption and by binding of 125I staph protein A.

The amount of IgG in the serum of patients with suspected immune neutropenia that binds to normal paraformaldehyde-fixed human granulocytes was measured simultaneously by a quantitative antiglobulin consumption assay and by binding of 125I-staphylococcal protein A (SPA). There was a significant linear relationship between the results of these two assays for the sera of 42 different patients. However, SPA binding appeared more sensitive than the quantitative antiglobulin assay for determining IgG antigranulocyte antibodies in serum. In a patient with Felty's syndrome who underwent splenectomy, the results of both assays on sequential serum samples correlated with clinical improvement. Thus, SPA binding appears to be a sensitive and reliable technique for measuring antigranulocyte antibodies, and there is a close correlation between antibody measured by antiglobulin consumption and those detected by SPA binding.