The reactivity of the antiserum is restricted to the Fc part of the IgA molecule. In immunoelectrophoresis and radial immunodiffusion, using various antiserum concentrations against normal swine serum a single precipitin line is obtained which shows a reaction of identity with the precipitin line obtained with purified IgA. No precipitation reaction is obtained with purified IgG, IgM, and IgG/Fab fragments. In precipitating techniques as immunoelectrophoresis and radial immunodiffusion to identify the presence of IgA in swine serum or other body fluids or to determine its concentration. To prepare an immunoadsorbent for the purification of swine IgA from serum or plasma. This antiserum is not intended for use in non-precipitating antibody-binding or other highly sensitive assays. This does not exclude the use of the antiserum in more sensitive techniques if proper controls are included.