Polymorphonuclear neutrophils (PMN) from 4 cows were preincubated (30 minutes, 37 C) in either actinomycin D (100 micrograms/ml) or puromycin (10 micrograms/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 IgG1, IgG2, IgM, or aggregated IgG (aIgG; 4 C, 12 hours) for flow 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 IgG2 in the presence or absence of 100-fold excess of IgG1, IgG2, and aIgG. Activation with rboIfn-gamma induced a 4.5-fold increase in binding of IgG1 and a fivefold increase in LMFC for IgG2. 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 IgG2 was inhibited by unlabeled IgG1, IgG2, and aIgG. Results indicate that bovine PMN Fc receptors (FcR) for IgG1 and IgG2 were rboIfn-gamma inducible, that induction required de novo transcription and translation, that a heterogeneous population of FcR exist on bovine PMN, and that IgG1 and IgG2 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.

A relation exists between colloid osmotic pressure and serum total protein concentration; equations describing this relation have been used to determine a calculated value for colloid osmotic pressure. However, the relation between total protein concentration and colloid osmotic pressure is altered by the method used to measure protein and by changes in the ratio of concentrations of albumin (A) to globulin (G). We developed nomograms for estimating colloid osmotic pressure from A and G concentrations, using samples obtained from clinically normal animals and compared the accuracy of these nomograms with that of previously described equations relating colloid osmotic pressure to total protein concentration. For comparison, serum samples from canine (n = 106), equine (n = 79), feline (n = 24), and bovine (n = 27) patients admitted to the University of Georgia Veterinary Medical Teaching Hospital were used. Results indicated that nomograms based on protein concentration estimated by a refractometer generally were the least reliable. Although predictive nomograms, using total protein concentration determined by the biuret method, provided better results for serum samples, there was considerable variation between measured and calculated values for colloid osmotic pressure in all species studied. Calculated values for colloid osmotic pressure derived from A and G concentrations were most closely related to measured values for colloid osmotic pressure in dogs, horses, and cats. However, calculated values for colloid osmotic pressure differed from measured values by as much as 5 mm of Hg for some samples by each of the methods of estimation. These results indicate that, although calculated values for colloid osmotic pressure may be most accurate when variations in the A-to-G ratio are accounted for in the nomogram, none of the calculation methods provided a consistently accurate estimate of colloid osmotic pressure.