Polymorphonuclear neutrophils (PMN) from 4 cows were preincubated (30 minutes, 37 C) in either actinomycin D (100 mu g/ml) or puromycin (10 mu g/ml), inhibitors of mRNA transcription and protein translation, or in medium 199. The PMN were incubated for a further 4.5 hours in medium containing 100 U of recombinant bovine interferon-gamma (rboIfn-gamma). The PMN were then incubated with bovine IgG(1), IgG(2), IgM, or aggregated IgG (aIgG; 4 C, 12 hours) for now cytometric analysis, using fluoresceinated isotype-specific antibody. The percentage of PMN binding the ligand and the logarithmic mean fluorescent channel (LMFC), an indicator of the amount of receptor (R) expression, were recorded. Competitive inhibition of ligand binding was measured by incubating PMN with fluoresceinated IgG(2) in the presence or absence of 100-fold excess of IgG(1), IgG(2), and aIgG. Activation with rboIEn-gamma induced a 4.5-fold increase in binding of IgG(1), and a fivefold increase in LMFC for IgG(2). These increases were inhibited by actinomycin D and puromycin. Percentage of PMN binding aIgG decreased after activation by rboIfn gamma. Interferon-gamma treatment did not affect binding or LMFC of IgM. However, binding of IgM was reduced by treatment with actinomycin D. Binding of fluoresceinated IgG(2) was inhibited by unlabeled IgG(1), IgG(2), and aIgG. Results indicate that bovine PMN Pc receptors (FcR) for IgG(1) and IgG(2) were rboIfn-gamma inducible, that induction required de novo transcription and translation, that a heterogeneous population of FcR exist on bovine PMN, and that IgG(1) and IgG(2) share a common FcR, Further, bovine PMN are capable of gene activation and are responsive to changes in their environment, thus being amenable to modulation for effective pathogen destruction.
