Ricin at Subpicomole Concentrations Induce Cytolytic Activity and Stimulate Lymphokine Secretion by Human Peripheral...

Human PBMCs were stimulated by ricin at very low concentrations (10(-14) M and lower) for 48 h at 37 degrees C. Cytolytic activity to K562 cell line and lymphokine secretion were been measured. PBMCs possessed the highest cytotoxicity (63 +/- 2.8% and 64 +/- 3.1%, respectively) to K562 cell line in the presence of 10(-15) M or 10(-16) M ricin. The high secretion of IL-1beta (2000 pg/ml), IL-2 (1300 pg/ml) and TNF-alpha (2200 pg/ml) was detected in the presence of 10(-15) M ricin. The mechanisms of the target cell death induced by PBMCs after co-incubation with various lectins: 10(-8) M phytohemagglutinin, 10(-8) M concanavalin A and ricin at 10(-15) M or 10(-16) M concentrations were compared. Internucleosomal DNA fragmentation characteristic of apoptotic mechanisms of the target cell death in all cases were observed, and the maximum of DNA fragmentation was registered in the presence of 10(-15) M ricin.