The toxic plant proteins ricin and abrin induce apoptotic changes in mammalian lymphoid tissues and intestine

The toxins ricin and abrin are potent inhibitors of protein synthesis. Apoptosis has been shown to be induced in some cells by cycloheximide and actinomycin D whereas the process is prevented in other cells by the same agents, both inhibitors of protein synthesis. We were interested to find whether ricin and abrin caused any apoptotic changes in rapidly dividing tissues where we believed that these toxins concentrate. Rats were injected intramuscularly with toxin and killed at time intervals, tissues being removed and examined by light and electron microscopy. Apoptotic-like bodies were abundant in para-aortic lymph nodes, Peyer's patches and ideal crypts of ricin or abrin intoxicated rats. Abrin was found to cause markedly more pronounced changes in these tissues, when compared with a similar dose of ricin. Prior to this, these toxins have been reported as causing necrosis in animal tissues.