Fragments of IgE antibodies in human feces.

The gel filtration profile of immunoglobulin E (IgE) in extracts of feces from 2 children was compared with IgE myeloma protein which had been exposed to proteolytic digestion by chymotrypsin. The peak of the chymotrypsin-digested IgE myeloma protein was found to be similar to that of fecal IgE after an elution volume between those of albumin and myoglobin, corresponding to a molecular weight of approximately 40,000 daltons. In the fractions where the peak of fecal IgE was found, no evidence for the presence of specific IgE antibodies (measured by RAST) could be detected. Fecal IgE could be purified by using an immunosorbent column to which rabbit antihuman IgE was coupled. Sufficient amounts of fecal IgE could thus be obtained and used in autoradiographic experiments. The IgE-containing fractions could also be detected with 125I-labelled second antibodies to visualize the IgE precipitates.