A simple spot technique for thin layer immunoassays (TIA) on plastic surfaces.

A simple and sensitive technique for visualization of antigen--antibody reactions is described. The property of many antigens to become adsorbed firmly on to a hydrophobic polystyrene surface while retaining their serological reactivity is taken advantage of. On a surface with adsorbed antigen the corresponding immune serum is applied spot-wise. The antigen--antibody reaction areas on the surface are characterized by a distinct hydrophilic condensation pattern when exposed to water vapour. The results obtained by the immunoassay technique described can be reproduced with great accuracy. The method is well suited for quantitative determination of a wide range of antigens as well as their corresponding antibodies. Antigen concentrations of 0.2--0.8 mg/l and antibody concentrations about 1 mg/l can be detected. By employing an antiimmunoglobulin serum subsequent to the primary antigen--antibody reaction, an increase in sensitivity can be obtained.