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Chicken macrophages are the most potent antigen-presenting cells capable of resistance to exogenous pathogenic microorganisms. 1–6 Macrophages differentiate via classic or alternative pathways into 2 functional types: M1 or M2. 7 Activated

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in American Journal of Veterinary Research

Platelet-activating factor (1- O -hexadecyl-2-acetyl sn -glycero-3-phosphocholine) is a phospholipid produced by a variety of cells, including mast cells, basophils, eosinophils, neutrophils, and endothelial cells. 1 Platelet-activating factor

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in American Journal of Veterinary Research

STAT-6), or Treg (TGF-β, IL-10, and Foxp3). As an example, IL-4 activates STAT-6 and GATA-3 through binding to its receptor on Th2 cells, leading to transcription of additional IL-4 and other Th2 cytokines, and at the same time production of IFN-γ is

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in American Journal of Veterinary Research

through alterations in the intracellular concentrations of cAMP and cGMP. 2 This can be brought about by activation of adenylyl or guanylyl cyclase or by an alteration in the activity of PDE, which breaks down these cyclic nucleotides. Phosphodiesterases

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in American Journal of Veterinary Research

activation as part of the respiratory burst, and because the MPO index estimates the intracellular content of MPO per neutrophil, decreases in MPO index are thought to occur secondary to neutrophil degranulation. 6 The stage of the myelopoietic response to

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in American Journal of Veterinary Research

SUMMARY

The activation of the complement system of rainbow trout by trout C-reactive protein (crp) was investigated. Complement fixation tests were performed by using rabbit hemolysin-sensitized sheep erythrocytes and rainbow trout complement. Purified crp increased the consumption of complement in the presence of Streptococcus pneumoniae C-polysaccharide (cps), indicating the activation of the complement system. In contrast to this, acute phase serum activated the complement in the absence of cps. Consumption of the complement by acute-phase serum was depressed when crp was removed from acute-phase serum by cps-sepharose 4B affinity chromatography. The acute-phase serum, as well as crp plus cps, suppressed in vitro growth of Vibrio anguillarum in the presence of complement, and enhanced the phagocytosis of the bacteria by glass-adherent peritoneal exudate cells. These results indicated that crp has a role in host defense during acute-phase response through the activation of the complement system, enhancement of phagocytosis, and suppression of bacterial growth.

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in American Journal of Veterinary Research

Abstract

Objectives

To investigate the role of extracellular Ca2+ and Mg2+ in aggregated IgG (algG)-mediated cellular activation, and to determine how algG-induced activation is coupled to Ca2+ homeostasis in bovine neutrophils.

Sample Population

4 clinically normal, lactating Holstein cows, in their second lactation, which ranged between 60 and 150 days.

Procedure

algG was prepared by heating bovine igG, and C5a was obtained by activating fetal bovine serum with zymosan. Luminol-amplified chemiluminescence (CL) of isolated neutrophils was measured in the presence of algG or phorbol 12-myristate 13-acetate (PMA). The reaction mixture contained either Hanks’ balanced salt solution or Ca2+- and Mg2+-free Hanks’ balanced salt solution. Binding of algG to neutrophils was measured by flow cytometry after incubation with fluorescein isothiocyanate-conjugated second antibody. Intracellular-free concentration [Ca2+] was measured in a fluorescence spectrofluorometer after incubation of neutrophils, loaded with the fluorescent dye fura-2 acetoxymethyl ester, with either algG or C5a.

Results

In a Ca2+- and Mg2+-containing reaction mixture, algG induced strong CL responses, whereas removal of extracellular divalent cations almost abolished the respiratory burst activity. The CL emission on stimulation with PMA was independent of extracellular Ca2+ and Mg2+. Examination of cells by flow cytometry after incubation with algG indicated that the binding of algG was identical in the presence and absence of extracellular Ca2+ and Mg2+. No increase in [Ca2+] was seen in fura-2 acetoxymethylester-loaded neutrophils after stimulation with algG. C5a induced a typical transient increase in [Ca2+].

Conclusions

algG-induced activation of bovine neutrophils is highly dependent on presence of extracellular divalent cations. This dependency is not caused by the need of divalent cations for binding of algG by neutrophils or because the influx of Ca2+ from the extracellular space is an integral component of algG-mediated activation pathway. Because need for extracellular Ca2+ and Mg2+ could be partially circumvented by pretreating neutrophils with PMA, it is possible that this activation pathway may involve a protein kinase C, which is not directly coupled to receptors for algG. (Am J Vet Res 1996;57:1312-1316)

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in American Journal of Veterinary Research

compromised pigs. Peroxisome proliferator-activated receptors, members of the nuclear hormone receptor superfamily, are ligand-activated transcription factors that include PPARα, PPARβ, and PPARγ 4 The PPARs regulate gene expression by binding (with the

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in American Journal of Veterinary Research

Summary

The type of plasminogen activator (pa) produced by bovine milk macrophages has been determined. Macrophages produce a pa protein with molecular weight of 28,000 and isoelectric point of 8.5, and with enzymatic activity independent of fibrin. These characteristics are identical to those reported for bovine urokinase-pa. Although blood monocytes and milk macrophages produce pa after stimulation with lipopolysaccharide, mammary macrophages are clearly limited in their ability to release pa. At maximal stimulation, 78% of the pa produced by milk macrophages remained cell-associated. In marked contrast, blood monocytes released 76% of the pa produced into the culture medium. Macrophages isolated from mastitic quarters produced higher (2.5 times) amounts of pa, compared with those produced by macrophages isolated from healthy quarters. However, in both cases, macrophages were unable to secrete the protein already produced. The limited pa secretion by milk macrophages might be a residual function of a differentiated macrophage population.

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in American Journal of Veterinary Research

SUMMARY

Objective

To investigate whether platelet-activating factor (PAF) primes the porcine pulmonary response to lipopolysaccharide (LPS), and what effect PAF priming has on porcine neutrophil superoxide (SO) release.

Animals

8- to 10-week old pigs.

Procedures

After pigs were anesthetized with sodium pentobarbital and instrumented for standard cardiopulmonary hemodynamic measurements, they were randomly assigned to receive PAF (0.1 ng/kg of body weight/min, 0 to 2 hours) plus saline solution (2 to 6 hours), saline solution (0 to 2 hours) plus LPS (0.25 μg/kg/h, 2 to 6 hours), or PAF plus LPS. Cardiopulmonary variables were measured throughout the study. Neutrophils were isolated from saline- or PAF-treated pigs at 0 (baseline) and 2 hours, and the effect of in vivo PAF exposure on ex vivo phorbol myristate acetate (PMA)-induced SO release was measured. Additionally, neutrophils isolated from immune-naive pigs were primed in vitro for 10 minutes with 10 μM PAF, and PMA-induced SO release was measured.

Results

PAF infusion significantly enhanced the increase in mean pulmonary arterial pressure, pulmonary vascular resistance, and hypoxemia associated with LPS administration. The infusion increased ex vivo neutrophil SO release, and in vitro PAF exposure primed neutrophils for enhanced SO release that was inhibited by pretreatment of cells with indomethacin.

Conclusions

PAF primes the porcine pulmonary system for the response to LPS. It primes porcine neutrophils in vivo and in vitro for PMA-induced SO release, and in vitro priming is mediated by cyclooxygenase products of arachidonic acid metabolism.

Clinical Relevance

PAF may modulate the porcine inflammatory response by acting as a priming agent, making pigs more responsive to the negative effects of bacterial LPS. (Am J Vet Res 1997;58:1386–1391)

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in American Journal of Veterinary Research