Heterogeneity of human polyclonal IgE reacting with staphylococcal protein A

A small part of polyclonal IgE (6%) was bound to protein A-Sepharose from the serum of M.P., containing a high concentration of IgE. No monoclonal IgE isolated from the serum of V.L. was bound to this sorbent. This binding of polyclonal IgE appears to be heterogeneous since a multiphasic pattern was observed with discontinuous pH gradient elution from protein A-Sepharose. Also, like IgE from the whole serum, monomeric IgE isolated from the serum of M.P. on Sepharose 6B showed this binding heterogeneity. It is suggested that IgE molecules with different affinities for protein A could belong to different isotypic or allotypic variants.