Screening for bacterial Fc-receptor activity on nitrocellulose membranes

Fc receptors released from staphylococci and streptococci could be readily detected by direct cultivation of the bacteria on nitrocellulose membranes or by microfiltration of their culture supernatants. The nitrocellulose membranes used in both assays were subsequently treated with human immunoglobulin (Ig) G. The reactions of the Fc receptor with IgG could be demonstrated by use of the respective peroxidase-labelled antibodies against IgG. The resulting color formation, which indicated Fc-receptor activity of the bacterial culture, closely corresponded to the 125I-labelled IgG-binding reactivity.