Similarities Between Ige In Human Feces And A Chymotrypsin-Digest Of An Ige Myeloma Protein

Immunoglobulin E (IgE) in human feces was characterized by radioimmunoassays with different specificities of the second antibodies, and by immunoprecipitation techniques. The fecal IgE was compared with an intact IgE myeloma protein and with Fc'' fragments of the IgE molecules, obtained after prolonged chymotrypsin-digestion of the IgE myeloma protein. The experiments showed that both the fecal IgE and Fc'' fragments shared the D epsilon 1 antigenic determinants while the intact IgE had both D epsilon 1 and D epsilon 2 determinants. They also shared thermal stability at 56 degrees C as compared to intact IgE. Fecal IgE and Fc'' fragments both showed rapid anodal migration in an electric field, different to that of intact IgE. A tandem crossed immunoelectrophoresis technique provided signs of immunological identity between the precipitates of fecal IgE and those of the Fc'' fragments. It is therefore likely that most, if not all, IgE in human feces consists of Fc" fragments.