The use of radioimmune assay in investigating reagents to be used in the immunocytochemical localization of hepatitis B surface antigen in immune complexes in the kidney of patients with membranous nephropathy and Australia antigenaemia.

Radioimmune assay (RIA) was used to investigate the effect of fixatives on antigenicity of the hepatitis B surface antigen (HBsAg) and the effect of pronase on the elution of antibody (Ab) from the HBsAG-Ab complex. The effect of pronase on Ab elution was also tested on sections of kidney from a patient with the immune complex disease systemic lupus erythematosus (SLE). Immunoglobulin G (IgG) was located in pronase treated and untreated sections using the indirect immunoperoxidase technique. Glutaraldehyde was shown to be the fixative of choice for studies involving HbsAG. All fixatives were shown to have less effect on antigenicity at 4 degrees C than at room temperature. Osmium tetroxide reduced antigenicity to one-third, even at 4 degrees C. RIA and SLE kidney section studies showed that Ab was eluted from immune complexes by pronase. Pre-fixation of the antigen (Ag) by glutaraldehyde appears to have no effect on the final elution, although fixation after pronase treatment seemed to enhance the elution effects. The availability of an RIA kit with HBsAg- and AB-coated beads was of great assistance in evaluating reagents to be used in immunoperoxidase studies of HBsAg in immune complexes of patients with membranous nephropathy and Australia antigenaemia.