Grain dust contains a tannin-like material which fixes complement.

Grain dust extract has been found to activate complement. We investigated the possibility that this activity was due to tannin by comparing the characteristics of grain dust extract with those of tannic acid. The properties that were studied were the interaction with albumin and immunoglobulin G, the stability to heat, and the adsorption to polyvinylpolypyrrolidone and hide powder. Grain dust extract was found to show similarities with tannic acid which were consistent with the presence of tannin accounting for most of its complement fixing activity.