MODULATION OF FC-RECEPTORS FOR IGG ON BOVINE POLYMORPHONUCLEAR NEUTROPHILS BY INTERFERON-GAMMA THROUGH DE-NOVO RNA-TRANSCRIPTION AND PROTEIN-SYNTHESIS

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 medi um containing 100 U of recombinant bovine interferon-gamma (rboIfn-gam ma). The PMN were then incubated with bovine IgG(1), IgG(2), IgM, or a ggregated IgG (aIgG; 4 C, 12 hours) for now cytometric analysis, using fluoresceinated isotype-specific antibody. The percentage of PMN bind ing the ligand and the logarithmic mean fluorescent channel (LMFC), an indicator of the amount of receptor (R) expression, were recorded. Co mpetitive inhibition of ligand binding was measured by incubating PMN with fluoresceinated IgG(2) in the presence or absence of 100-fold exc ess 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 L MFC for IgG(2). These increases were inhibited by actinomycin D and pu romycin. Percentage of PMN binding aIgG decreased after activation by rboIfn gamma. Interferon-gamma treatment did not affect binding or LMF C of IgM. However, binding of IgM was reduced by treatment with actino mycin D. Binding of fluoresceinated IgG(2) was inhibited by unlabeled IgG(1), IgG(2), and aIgG. Results indicate that bovine PMN Pc receptor s (FcR) for IgG(1) and IgG(2) were rboIfn-gamma inducible, that induct ion required de novo transcription and translation, that a heterogeneo us population of FcR exist on bovine PMN, and that IgG(1) and IgG(2) s hare a common FcR, Further, bovine PMN are capable of gene activation and are responsive to changes in their environment, thus being amenabl e to modulation for effective pathogen destruction.