Pathological aspects of ricin toxicity in mammalian lymph node and spleen.

In an earlier study (Griffiths et al., 1987) we demonstrated that two toxic plant proteins, ricin and abrin bring about apoptotic rather than necrotic cell death in mammalian lymphoid tissues and intestine. Here we expand upon the previous study, and report further observations relating purely to ricin and its pathology in lymph node and spleen. Rats were injected with ricin and killed at time intervals, tissue being excised and examined by light or electron microscopy. As well as previously reported apoptotic changes in the lymph node, we observed sinusoidal haemorrhage accompanied by erythrophagocytosis and loss of normal structure. With the aid of lymphocyte typing, we noticed a complete relocation of T and B lymphocyte populations, with destruction of B cells. Follicular centres of the spleen exhibited similar pathology to that seen in lymph nodes, along with loss of lymphocytes in areas adjacent to the central artery of the peri-arteriolar lymphoid sheath (PALS).