GROWTH-INHIBITORY EFFECT OF BOVINE LACTOFERRIN TO TOXOPLASMA-GONDII TACHYZOITES IN MURINE MACROPHAGES - TYROSINE PHOSPHORYLATION IN MURINE MACROPHAGES INDUCED BY BOVINE LACTOFERRIN

Previous studies have shown that lactoferrin induces growth inhibitory effects in mouse macrophages against intracellular Toxoplasma gondii, and these effects were not mediated by the oxygen-dependent and inorg anic nitrogen-dependent pathway. To clarify the mechanism of anti-Toxo plasma gondii activity induced by lactoferrin, we examined whether lac toferrin promoted the phosphorylation of tyrosine residues in macropha ge proteins. In immunoblotting assays using anti-[phosphorylated tyros ine] monoclonal antibody, phosphorylation of tyrosine residues was det ected in protein(s) of approximately 30 kDa in macrophages incubated w ith lactoferrin. Inhibition of the lactoferrin-induced tyrosine-phosph orylation by genistein led to loss of the lactoferrin-induced growth i nhibitory effect against the parasites. These findings suggest that la ctoferrin induces tyrosine-phosphorylation in macrophages, and the tyr osine phosphorylation seems to be associated with the induction of the growth inhibitory activity exerted against intracellular Toxoplasma g ondii.