Isoelectric focusing of human IgA and secretory proteins using thin layer agarose gels and nitrocellulose capillary blotting.

A simple, rapid and economical method for focusing human immunoglobulin A in low electroendosmosis agarose is described. IgA preparations isolated from serum and secretions were focused with high resolution in thin layer gels. Serum and milk proteins were transferred to nitrocellulose sheets by capillary blotting and the spectrotype of total IgA determined with radiolabeled anti-human IgA antibodies. These studies indicated that the spectrotype of human IgA extends between the pH range 4.3-6.85. The spectrotypes of free secretory component and alpha-1 antitrypsin released from an IgA myeloma protein were determined by a similar technique. These methods should prove useful in determining the diversity of IgA antibodies whether or not the starting material is pure.