Immunocytochemical detection of ricin. II. Further studies using the immunoperoxidase method.

Radio-iodinated ricin was injected into rat muscle in vivo to establish the distribution of the toxin at various time intervals after injection. Injection site muscle and para-aortic lymph nodes were selected for localization of ricin by the immunoperoxidase technique. Sections of snap-frozen tissues were fixed using a variety of methods to establish the best protocol for the immunodetection method. This was found to be with an ether-ethanol mixture. Ricin was detected in tissue at the site of injection taken from rats sacrificed 1, 4, 8 and 24 h after injection and in tissue from animals dying from ricin intoxication after about 30 h. This method, however, failed to demonstrate unequivocally the presence of ricin in lymphoid tissue which had been indicated by the radiotracer study. The significance of these findings and their relevance to forensic diagnosis are discussed.