In vitro effect of swainsonine on bovine and ovine lymphoblastogenesis.

Peripheral blood lymphocytes (PBL) were obtained from heifers and wethers to assess the in vitro effects of swainsonine. Stimulated and unstimulated PBL (2x10(5)/well; 96 well plates) were incubated in the presence of swainsonine (2, .2, .02, .002, and 0 microg/mL; n = 32) for 72 h. Mitogens used to stimulate PBL were concanavalin A (ConA; 5 microg/mL), phytohemagglutinin-P (PHA-P; 5 microg/mL), phytohemagglutinin-M (PHA-M; 5 microg/mL), pokeweed mitogen (PWM; 5 microg/mL), and lipopolysaccharide (LPS; 10 microg/mL). Controls received no swainsonine or mitogen. Effects of swainsonine are expressed as a percentage of stimulation relative to control (stimulation index; SI). Unstimulated bovine PBL treated with 2 microg/mL of swainsonine exhibited a depressed (P<.001; SI of 87 and 100 for 2 microg/mL and control, respectively; SE = 2.7) SI. At concentrations of .2 and 2 microg/mL, swainsonine inhibited (P<.001; SI of 351, 310, and 464 for .2, 2, and 0 microg/mL, respectively; SE = 27.1) bovine PBL proliferative response to PHA-P. Swainsonine had a mitogenic effect on unstimulated ovine PBL at .2 and 2 microg/mL (P<.05; SI of 118, 113, and 100 for .2 and 2 microg/mL and control, respectively; SE = 4.4). Swainsonine inhibited ovine proliferative responses to PHA-P at .2 and 2 microg/mL (P<.005; SI of 190, 178, and 228 for .2, 2, and 0 microg/mL, respectively; SE = 9.4) and to PHA-M at .002 and 2 microg/mL (P<.03; SI of 165, 167, and 192 for .002, 2, and 0 microg/mL, respectively; SE = 7.9). The opposing responses of unstimulated ovine (mitogenic) and bovine (antiproliferative) PBL to swainsonine indicates a differential species response. Swainsonine suppression of PHA-P-induced proliferation would indicate a negative effect on ovine and bovine T-cell function.