Intestinal pathology following intramuscular ricin poisoning

Within the gut, intramuscular ricin poisoning results in major pathological changes. Immunocytochemistry and electron microscopy illustrate that these changes appear confined to the small intestine, the stomach and large intestine remaining virtually unaffected. These changes include apoptosis crypt and mucosal epithelial cells, hydropic change in enterocytes, infiltration of large numbers of plasma cells into the lamina propria, subsequent apoptosis of many of the plasma cells, and the appearance within the lamina propria of highly active macrophages. Of these changes, greatest significance is attached to the infiltration and apoptosis of large numbers of plasma cells. This is not a common pathological feature within the gastro-intestinal tract, and may prove to be specifically diagnostic for ricin or a group of toxins having structurally similar characteristics. In this study, the toxin was administered by intramuscular injection and not orally; considering this mode of administration, damage to the small intestine was far more severe than might perhaps be expected. The intensity of cellular infiltration within the lamina propria is especially interesting, as it appears to be more analogous to a local immune response triggered by an oral toxin rather than one administered by an intramuscular route.