Effects of thiabendazole on dexamethasone-induced suppression of lymphocyte and neutrophil function in cattle.

Seven dosage levels of thiabendazole were evaluated for their ability to normalize lymphocyte or neutrophil function in dexamethasone-treated cattle. Dexamethasone administration (0.04 mg/kg intramuscularly daily for 3 days) significantly suppressed the lymphocyte blastogenic response to phytohemagglutinin, concanavalin A, and pokeweed mitogen. The lymphocyte blastogenic response to allogeneic lymphocytes was also suppressed in dexamethasone-treated cattle, but this effect was not statistically significant. Neutrophils from dexamethasone-treated cattle had a significantly enhanced ability to migrate under agarose, and significantly suppressed ability to reduce nitroblue tetrazolium, iodinate protein, and mediate antibody-dependent cell-mediated cytotoxicity. Thiabendazole when administered concurrently with dexamethasone in the dosage range from 1.0 to 25.0 mg/kg (orally) did significantly enhance lymphocyte blastogenic responsiveness to phytohemagglutinin, concanavalin A, pokeweed mitogen and allogeneic cells (in dexamethasone-treated cattle). This immunonormalizing effect was not observed at the 50 or 100 mg/kg dosage levels. Thiabendazole did not produce a consistent significant enhancement of any parameter of neutrophil function in dexamethasone-treated cattle.