Measurement of glial fibrillary acidic protein (GFAP) and anti-GFAP antibodies by solid-phase radioimmunoassays.

A solid-phase radioimmunoassay was developed for the detection of glial fibrillary acidic protein (GFAP) and GFAP-specific immunoglobulin G (IgG) antibodies. In antibody assays purified GFAP was absorbed onto polystyrene beads, followed by incubation in dilutions of serum. (125-I)-labelled human anti-IgG was used to quantify antibodies bound to solid-phase GFAP. GFAP in samples was measured by the inhibition of the binding of anti-GFAP antibody to solid-phase GFAP. The serum and CSF samples of 19 brain tumor, 40 multiple sclerosis and 66 control patients were assayed for anti-GFAP antibodies. The binding values in the serum and CSF samples of the brain tumor patient group were higher and the binding values in the CSF samples of the multiple sclerosis group lower than those of the control group. The differences were statistically significant.