In normal adult serum, the approximate percentage composition of IgA with respect to is subclasses is IgA1:90percent and IgA2:10percent. In secretory IgA, the subclass proportions may approach 50:50. The clinical significance of the subclasses has yet to be determined. Single arc by IEP against antisera to whole human serum, human IgA2, and human kappa. Not immunoreactive to antisera against human IgA1, IgG, IgD, IgE, IgM, and lambda by IEP. Prepared from myeloma plasma shown to be non reactive for HbsAG, anti-HCV, anti-HBc, and negative for anti-HIV 1 & 2 by FDA approved tests. >95percent pure by SDS-PAGE.