Immunosorbent assay of interactions between human parotid immunoglobulin A and dietary lectins.

By enzyme-linked immunosorbent assay (ELISA), parotid IgA was found to associate with purified peanut (PNA), pea (PSA) and wheat-germ (WGA) lectins. To determine the effect of eating foods which contained these lectins on the reactivity of IgA with purified lectins, samples of parotid saliva were collected prior to, and after, eating the lectin-containing food and their reactivity determined by ELISA. Four of 5, and 5 of 6 subjects, respectively, gave one or more post-eating samples with increased IgA reactivity to purified PNA or PSA, but not to WGA, a heterologous lectin. Four of 6 subjects had significantly higher IgA reactivity with PSA after they ate raw peas on a single occasion. Absorption experiments with PSA and PNA conjugated to agarose beads showed there were different populations of IgA molecules which reacted with the lectins. One highly-reactive population increased after eating the lectin-containing food and may contain antibodies induced by antigenic determinants in the lectin. The lectins may also bind to saccharide moieties of the IgA molecules.