Passage of undegraded dietary antigen into the blood of healthy adults. Quantification, estimation of size distribution, and relation of uptake to levels of specific antibodies.

The absorption into the blood of ovalbumin (OA) and beta-lactoglobulin (BLG) was investigated in eight healthy adults. Enzyme immunoassays showed up to 10.5 ng OA/ml serum in seven out of eight individuals 2-3 h after a test meal, whereas no BLG was demonstrated. The apparent size distribution of the absorbed OA was investigated by high-pressure liquid gel permeation chromatography fractionation, followed by enzyme-linked immunosorbent assay, which in the fractionated sera showed OA in all eight individuals. OA was found at the elution volume of intact OA and, in addition, was present in high molecular weight fractions, as part of the immune complexes. The serum concentrations of OA could not be clearly correlated to levels of serum and secretory anti-OA antibodies. No significant alterations of the levels of circulating immune complexes could be demonstrated by two antigen-nonspecific assays. The presented data indicate that, for certain dietary proteins, low-grade absorption of apparently undegraded protein into the blood occurs regularly in healthy adults.