Antibodies to granulocytes detected by an indirect immunofluorescence method not requiring chemical modification of cells.

IgG antibodies to neutrophil polymorphonuclear cells (PMNs) were detected by a simple indirect immunofluorescence method that did not require chemical or enzymatic modification of the cells. Based on recent information about the human PMN Fc gamma-receptor, nonspecific binding of IgG to PMNs was virtually completely prevented by incubating cells at 37 degrees C with human serum diluted 1 to 3 in the presence of a high concentration of rabbit IgG. This also facilitated distinction of sera with weak anti-PMN activity from normal sera. On the other hand, nonspecific staining remained on a fraction (10-25%) of mononuclear leukocytes. Following first-time transfusion of 0.5 to 5 units of whole blood or red cell concentrate, 4 of 27 patients (15%) developed anti-leukocyte antibodies. Anti-leukocyte antibodies were detected in 51 percent of 47 patients with reported febrile transfusion reactions; the IgG antibodies bound to PMNs in 38 percent of these 47 patients. Since only about one in three patients with febrile transfusion reactions had detectable IgG anti-PMN antibodies, fever may be caused by lysis of leukocytes other than PMNs.