Preliminary investigation of the mechanism of inhibition of bovine lymphocyte proliferation by Pasteurella haemolytica A1 leukotoxin

Pasteurella haemolytica A1 leukotoxic culture supernate has been shown to inhibit bovine lymphocyte blastogenesis induced by concanavalin A (Con A), pokeweed mitogen (PWM) and purified protein derivative (PPD). The various mechanisms by which this inhibition could be overcome were investigated in an effort to determine at which stage of cell activation the leukotoxin exerted its inhibitory effect. For both Con A and PWM stimulated cultures, the addition of partially purified bovine interleukin 1 reduced the leukotoxin-induced inhibition. Recombinant interleukin 2 had a similar effect. Addition of the glycolipid, monosialoganglioside was also able partially to overcome the inhibition.