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. No reaction by IEP to IgA2 antiserum. 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.