Toxins in the skin secretion of the oriental catfish (Plotosus lineatus): immunological properties and immunocytochemical identification of producing cells.

Antiserum against toxin I, one of the lethal factors in the skin secretion from the oriental catfish (Plotosus lineatus), was used to examine immunological properties of the toxic factors and identify toxin-producing cells by an immunocytochemical technique. In immunodiffusion tests, the antiserum formed a precipitin line with toxin I while it formed no precipitin line either with another lethal factor (toxin II) or with a hemolysin. Lethal and edema-forming activities of toxin I were neutralized by the antiserum but lethal activity of toxin II and lytic activity of the hemolysin were not. These results suggested that toxin I can be antigenically distinguished from both toxin II and hemolysin. In immunocytochemical tests using the antiserum, club cells in the epidermis were positively stained, indicating that toxin I is produced in the club cells. Interestingly, venom glandular cells surrounding the dorsal and pectoral spines were also stained. The venom glandular cells appear to produce toxin I or a toxin with the same antigen determinants as toxin I.