Quantitative estimation of secretory immunoglobulin A by radial immunodiffusion technique.

A single radial diffusion system in agar gel, which can be used for the quantitative measurement of secretory immunoglobulin A in solutions and in biological fluids, is discussed. Concentrations of secretory immunoglobulin A as low as 0.095 mg/ml were measured successfully using a 2 mul sample volume. Conditions that achieve maximum sensitivity and precision, such as gel concentration, incubation time, and temperature, are described.