Influence of recombinant bovine gamma interferon on neutrophil function

Steinbeck, Marla
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To determine the role of cytokines in enhancing neutrophil function, peripheral blood neutrophils from healthy cattle were preincubated with recombinant bovine gamma interferon (rboIFN-gamma). Pretreatment of neutrophils with rboIFN-gamma activated neutrophils to have enhanced antibody-dependent (ADCC) and -independent (AINC) cytotoxicity and impaired random migration. Neutrophil ingestion, superoxide anion production, and iodination activity were not consistently affected by rboIFN-gamma pretreatment. In order to better understand the activation process, the molecular events involved in the enhancement of neutrophil cytotoxicity and the inhibition random migration were investigated. Both RNA and protein syntheses by neutrophils were required for the enhancement of AINC activity and the inhibition of random migration, but were not required for the enhancement of ADCC by rboIFN-gamma. Specifically, rbo-IFN-gamma treatment of neutrophils enhanced the expression of two major proteins of molecular mass 60,000 and 94,000 as determined by SDS-polyacrylamide, linear-gradient gel electrophoresis and [superscript]35S-fluorography. Neutrophils isolated from cattle immunosuppressed by administration of glucocorticoids (dexamethasone) had depressed arachidonic acid metabolism, AINC, and ADCC activities and enhanced random migration. Recombinant boIFN-gamma treatment of these neutrophils (in vitro) did not enhance AINC, but reversed the suppression of ADCC and inhibited random migration to approximately normal levels. The protein synthesis patterns in the presence and absence of rboIFN-gamma were similar to those of neutrophils from nondexamethasone-treated cattle. Inhibitors of arachidonic acid metabolism, nordihydroguaiaretic acid and BW755c, inhibited the ability of rboIFN-gamma to induce AINC activity, but did not enhance ADCC or inhibit random migration of neutrophils isolated from nontreated cattle. There was also a difference in the ability of bovine and human neutrophils to express AINC activity after homologous gamma interferon treatment. Media conditions were varied and although this affected the bovine neutrophil AINC activity, no enhancement of human neutrophil AINC activity by human gamma interferon occurred in any media evaluated.