Chemotactic competence of neutrophils from neonatal calves. Functional comparison with neutrophils from adult cattle

Effect of Gammulin supplementation during the first 24 d of life on health, growth, and first-lactation performance of Holstein cows

Development and health during calfhood are paramount for the success of dairy operations because they are associated with longevity and productivity later in life. Thus, provision of nutritional supplements has been explored as an alternative to improve growth of preweaned calves. Holstein calves (female = 472, male = 46) from 2 dairies located in the San Joaquin Valley were assigned randomly to receive 25 g/d of Gammulin (APC Inc.) from 2 to 24 d of age (GAM = 263) or to receive no supplementation (control = 255). Calves were fed a mixture of waste milk and milk replacer (3.79 L/d), and study personnel added the supplement to the bottles of calves in the GAM treatment daily. Study personnel monitored calves 6 d/wk and recorded starter intake, fecal score (1 = firm, 4 = watery), and attitude score (1 = alert and responsive, 4 = recumbent). Blood samples were collected (4, 7, 14, 26, 44, 56, and 68 d of age) to determine concentrations of total protein, glucose (n = 64), nonesterified fatty acids (n = 64), β-hydroxybutyrate (n = 171), and hematocrit (n = 518). Calves (n = 64) were treated with 0.5 mg of ovalbumin at 3, 21, and 42 d of age, and concentration of anti-ovalbumin IgG was measured. The percentage of polymorphonuclear leukocytes positive for phagocytosis and oxidative burst after the ex vivo exposure to an enteropathogenic Escherichia coli was evaluated (n = 64). We followed the female calves through the end of the first lactation or until they left the herd to evaluate the effect of treatment on first-lactation performance. Treatment did not affect metabolic and immune responses. During the supplementation (1 to 24 d of age), starter intake did not differ between treatments, but the GAM treatment reduced starter intake (638.5 ± 1.1 vs. 696.6 ± 1.1 g/d; mean ± standard error of the mean) from 25 to 60 d of age and average daily gain (798.8 ± 15.4 and 749.5 ± 15.2) from 23 to 60 d of age, resulting in reduced body weight at 60 d of age (68.4 ± 0.4 vs. 69.8 ± 0.5 kg). From 1 to 24 d of age, GAM treatment reduced the number of days calves had fecal score = 4 (ratio of number of days = 0.92; 95% confidence interval = 0.84-1.00) and it reduced the number of electrolyte treatments calves received (ratio of number of treatments = 0.92; 95% confidence interval = 0.85-0.99). Treatment did not affect the hazard of first calving and first-lactation 305-d milk yield, but the adjusted hazard ratio (0.82; 95% confidence interval = 0.65, 1.04) of pregnancy in the first lactation tended to be reduced for the GAM treatment. In the conditions of this experiment, supplementation with 25 g/d of GAM to the liquid feed from 2 to 24 d of age did not improve calfhood health and performance.

Short communication: Effect of granulocyte-macrophage colony-stimulating factor on neonatal calf peripheral blood neutrophil function in vitro

Neutrophils are innate immunity cells that represent the first line of cellular defense against invading pathogens. Dairy calves, however, experience neutrophil dysfunction during the first weeks of age, contributing to increased disease susceptibility during this period. Granulocyte-macrophage colony-stimulating factor (GM-CSF) is a cytokine that improves neutrophil function in neonates of other species and mature cows. However, its capability to improve neonatal calf neutrophil function is unknown. Therefore, our objective was to evaluate the effect of GM-CSF on the functional capabilities of neutrophils of neonatal calves in vitro. We hypothesized that supplementation of neonatal neutrophils with GM-CSF would increase microbicidal functions to levels comparable with those of mature immunocompetent cattle. For this, we isolated blood neutrophils from 12 healthy 2- to 3-d-old Holstein calves, and neutrophils from 6 mid-lactation Holstein cows were used as a reference of robust neutrophil function. Subsequently, neutrophils from both calves and cattle were incubated for 9 h with 4 concentrations (0, 0.005, 0.05, or 0.5 µg/mL) of GM-CSF, and microbicidal function of neutrophils was assessed in terms of phagocytosis, respiratory burst, myeloperoxidase (MPO) activity, and extracellular trap formation. Mixed models with Tukey pairwise comparisons were used to identify differences among treatment and age groups. Supplementation of GM-CSF in vitro increased phagocytosis and MPO activity of calf and cow neutrophils, although not in a concentration-dependent manner. Respiratory burst and extracellular trap formation were not affected by GM-CSF supplementation. All the microbicidal capacity functions assessed were lower in neutrophils from calves, but supplementation with GM-CSF increased phagocytosis and MPO activity of calf neutrophils to levels comparable with unsupplemented cow neutrophils. Collectively, our results demonstrated that in vitro supplementation of calf neutrophils with GM-CSF enhanced some functional microbicidal capabilities to levels comparable with immunocompetent cattle. Hence, it may be possible to augment the functional capacity of calf neutrophils in vivo through the therapeutic application of GM-CSF and consequently enhance calves' resistance to infections. This should be tested in future in vivo studies.

Effect of age on the pharmacokinetics and distribution of tulathromycin in interstitial and pulmonary epithelial lining fluid in healthy calves

OBJECTIVE To compare the plasma pharmacokinetics of tulathromycin between 3-week-old (preweaned) and 6-month-old (weaned) calves and to characterize the distribution of tulathromcyin into pulmonary epithelial lining fluid (PELF) and interstitial fluid (ISF) of preweaned and weaned calves following SC administration of a single dose (2.5 mg/kg). ANIMALS 8 healthy 3-week-old and 8 healthy 6-month-old Holstein steers. PROCEDURES A jugular catheter and SC ultrafiltration probe were aseptically placed in the neck of each calf before tulathromycin administration. Blood, ISF, and bronchoalveolar lavage fluid samples were collected at predetermined times before and after tulathromycin administration for quantification of drug concentration. A urea dilution method was used to estimate tulathromycin concentration in PELF from that in bronchoalveolar lavage fluid. Tulathromycin-plasma protein binding was determined by in vitro methods. Plasma pharmacokinetics were determined by a 2-compartment model. Pharmacokinetic parameters and drug concentrations were compared between preweaned and weaned calves. RESULTS Clearance and volume of distribution per fraction of tulathromycin absorbed were significantly greater for weaned calves than preweaned calves. Tulathromycin-plasma protein binding was significantly greater for weaned calves than preweaned calves. Maximum PELF tulathromycin concentration was significantly greater than the maximum plasma and maximum ISF tulathromycin concentrations in both groups. CONCLUSIONS AND CLINICAL RELEVANCE Results suggested that age affected multiple pharmacokinetic parameters of tulathromycin, likely owing to physiologic changes as calves mature from preruminants to ruminants. Knowledge of those changes may be useful in the development of studies to evaluate potential dose adjustments during treatment of calves with respiratory tract disease.

The Vitamin D Binding Protein and Inflammatory Injury: A Mediator or Sentinel of Tissue Damage?

Neutrophils are the most abundant type of white blood cell in most mammals including humans. The primary role of these cells is host defense against microbes and clearance of tissue debris in order to facilitate wound healing and tissue regeneration. The recruitment of neutrophils from blood into tissues is a key step in this process and is mediated by numerous different chemoattractants. The neutrophil migratory response is essential for host defense and survival, but excessive tissue accumulation of neutrophils is observed in many inflammatory disorders and strongly correlates with disease pathology. The vitamin D binding protein (DBP) is a circulating multifunctional plasma protein that can significantly enhance the chemotactic activity of neutrophil chemoattractants both in vitro and in vivo. Recent in vivo studies using DBP deficient mice showed that DBP plays a larger and more central role during inflammation since it induces selective recruitment of neutrophils, and this cofactor function is not restricted to C5a, as prior in vitro studies indicated, but can enhance chemotaxis to many chemoattractants. DBP also is an extracellular scavenger for actin released from damaged/dead cells and formation of DBP-actin complexes is an immediate host response to tissue injury. Recent in vitro evidence indicates that DBP bound to G-actin, and not free DBP, functions as an indirect but essential cofactor for neutrophil migration. DBP-actin complexes always will be formed regardless of what initiated an inflammation, since release of actin from damaged cells is a common feature in all types of injury and DBP is abundant and ubiquitous in all extracellular fluids. Indeed, these complexes have been detected in blood and tissue fluids from both humans and experimental animals following various forms of injury. The published data strongly supports the premise that DBP-actin complexes are the functional neutrophil chemotactic cofactor that enhances neutrophil chemotaxis in vitro and augments neutrophilic inflammation in vivo. This review will assess the fundamental role of DBP in neutrophilic inflammation and injury.

Innate immune response in neonate Holstein heifer calves fed fresh or frozen colostrum

The aim of this research was to evaluate the influence of maternal cells from colostrum on the development and function of the innate immune response in Holstein calves. Calves were divided into 2 groups: COL + (n = 10) received fresh colostrum; and COL − (n = 10) which received frozen colostrum containing no viable cells. The calves were assessed before colostrum intake (D0), 48 h of age (D2), and weekly from D7 up to D28. Blood samples were collected for analysis of the distribution of leukocytes, cellular phenotype and in vitro granulocyte function. COL + calves tended to have a high number of neutrophils on D7 (p = 0.073). COL − calves took up significantly more Escherichia coli (measured as MFI) on D7 (p = 0.034). Endogenous production of radicals (as percentage of cells) tended to be higher in COL − calves on D14 (p = 0.061). The intensity of endogenous reactive oxygen species (ROS) produced by granulocytes tended to be higher in COL + calves on D21 (p = 0.094). Overall, ROS production (percent of cells, and MFI) induced by Staphylococcus aureus and Escherichia coli were higher in COL + calves than COL − calves. It was our observation that COL + calves developed an innate immune response more quickly and efficiently after natural exposure to pathogens after birth. In contrast, COL − calves mounted an innate response more slowly that yielded a persistent inflammatory response after natural exposure to these bacteria agents. This research provides evidence of an advantage to the calf of receiving fresh colostrum on the development and function of the innate immune system.

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Calves fed whole fresh colostrum (COL +) developed a fast and efficient innate immune response.

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Calves fed frozen colostrum (COL −) colostrum had a slow and persistent inflammatory response after natural challenge.

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COL + calves demonstrates advantages in relation to innate immune response against pathogens causing diarrhea.

Neutrophil recruitment to the lung in both C5a- and CXCL1-induced alveolitis is impaired in vitamin D-binding protein-deficient mice

Knowledge of how neutrophils respond to chemotactic signals in a complex inflammatory environment is not completely understood. Moreover, even less is known about factors in physiological fluids that regulate the activity of chemoattractants. The vitamin D-binding protein (DBP) has been shown to significantly enhance chemotaxis to complement activation peptide C5a using purified proteins in vitro, and by ex vivo depletion of DBP in physiological fluids, but this function has not been determined in vivo. DBP null ((-/-)) mice were used to investigate how a systemic absence of this plasma protein affects leukocyte recruitment in alveolitis models of lung inflammation. DBP(-/-) mice had significantly reduced (~50%) neutrophil recruitment to the lungs compared with their wild-type DBP(+/+) counterparts in three different alveolitis models, two acute and one chronic. The histology of DBP(-/-) mouse lungs also showed significantly less injury than wild-type animals. The chemotactic cofactor function of DBP appears to be selective for neutrophil recruitment, but, in contrast to previous in vitro results, in vivo DBP can enhance the activity of other chemoattractants, including CXCL1. The reduced neutrophil response in DBP(-/-) mice could be rescued to wild-type levels by administering exogenous DBP. Finally, in inflammatory fluids, DBP binds to G-actin released from damaged cells, and this complex may be the active chemotactic cofactor. To our knowledge, results show for the first time that DBP is a significant chemotactic cofactor in vivo and not specific for C5a, suggesting that this ubiquitous plasma protein may have a more significant role in neutrophil recruitment than previously recognized.

Cofactor regulation of C5a chemotactic activity in physiological fluids. Requirement for the vitamin D binding protein, thrombospondin-1 and its receptors

Factors in physiological fluids that regulate the chemotactic activity of complement activation peptides C5a and C5a des Arg are not well understood. The vitamin D binding protein (DBP) has been shown to significantly enhance chemotaxis to C5a/C5a des Arg. More recently, platelet-derived thrombospondin-1 (TSP-1) has been shown to facilitate the augmentation of C5a-induced chemotaxis by DBP. The objective of this study was to better characterize these chemotactic cofactors and investigate the role that cell surface TSP-1 receptors CD36 and CD47 may play in this process. The chemotactic activity in C-activated normal serum, citrated plasma, DBP-depleted serum or C5 depleted serum was determined for both normal human neutrophils and U937 cell line transfected with the C5a receptor (U937-C5aR). In addition, levels of C5a des Arg, DBP and TSP-1 in these fluids were measured by RIA or ELISA. Results show that there is a clear hierarchy with C5a being the essential primary signal (DBP or TSP-1 will not function in the absence of C5a), DBP the necessary cofactor and TSP-1 a dependent tertiary factor, since it cannot function to enhance chemotaxis to C5a without DBP. Measurement of the C5a-induced intracellular calcium flux confirmed the same hierarchy observed with chemotaxis. Moreover, analysis of bronchoalveolar lavage fluid (BALF) from patients with the adult respiratory distress syndrome (ARDS) demonstrated that C5a-dependent chemotactic activity is significantly decreased after anti-DBP treatment. Finally, results show that TSP-1 utilizes cell surface receptors CD36 and CD47 to augment chemotaxis, but DBP does not bind to TSP-1, CD36 or CD47. The results clearly demonstrate that C5a/C5a des Arg needs both DBP and TSP-1 for maximal chemotactic activity and suggest that the regulation of C5a chemotactic activity in physiological fluids is more complex than previously thought.

Upregulation of vitamin D binding protein (Gc-globulin) binding sites during neutrophil activation from a latent reservoir in azurophil granules

Vitamin D binding protein (DBP) is a multifunctional plasma transport protein that is also found on the surface of many cell types. Cell surface DBP significantly enhances chemotactic activity of complement (C) peptides C5a and C5a des Arg. However, both DBP binding and C5a chemotaxis enhancement can vary among neutrophil donors. To test if activation during cell purification is responsible for this variability, neutrophils were isolated using both standard and lipopolysaccharide (LPS)-free protocols. Cells isolated by the LPS-free method had no DBP-enhanced chemotaxis to C5a or DBP binding to plasma membranes. Moreover, neutrophils treated with LPS bound more avidity to immobilized DBP than sham-treated cells. Subcellular fractionation of neutrophils (standard protocol) revealed a heavy plasma membrane (HM) band that contained components of light plasma membranes and all three granules. The HM band possessed most of the DBP binding activity (58%), and activation of cells with ionomycin greatly increased DBP binding to HM. Azurophil granules contained 33% of the total DBP binding sites and there was a highly significant positive correlation (r=0.988) between release of the granule marker myeloperoxidase and DBP binding. These results indicate that fusion of granules with the plasma membrane forms HM that contains DBP binding sites.

CD44 and Annexin A2 Mediate the C5a Chemotactic Cofactor Function of the Vitamin D Binding Protein

The vitamin D binding protein (DBP) is a plasma protein that significantly enhances the chemotactic activity of C5a and C5a(desArg) (cochemotactic activity). The objective of this study was to investigate how DBP mediates this process using neutrophils and U937 cells transfected with the C5a receptor (U937-C5aR cells) and comparing chemotaxis to C-activated serum (DBP dependent) vs purified C5a (DBP independent). Binding to the cell surface is essential for this protein to function as a chemotactic cofactor, and DBP binds to a chondroitin sulfate proteoglycan (CSPG) on neutrophil plasma membrane preparations. To determine whether a CSPG also functions to mediate cochemotactic activity, U937-C5aR cells were grown in chlorate to inhibit CSPG sulfation or treated with chondroitinase AC. Either treatment significantly inhibited chemotaxis only to C-activated serum. CD44 is a major cell surface CSPG on leukocytes, and functions to facilitate chemotaxis. Treatment of cells with anti-CD44 blocks chemotaxis of neutrophils and U937-C5aR cells to C-activated serum but not purified C5a. DBP binds to CD44 on the cell surface as evidenced by coimmunoprecipitation, confocal microscopy, and cell binding studies. Annexin A2 associates with CD44 in lipid rafts; therefore, its potential role in mediating cochemotactic activity was investigated. Results demonstrate that anti-A2 inhibits neutrophil and U937-C5aR chemotaxis specifically to C-activated serum, blocks DBP binding to cells, and colocalizes with anti-DBP on the cell surface. These results provide clear evidence that CD44 and annexin A2 mediate the C5a chemotactic cofactor function of DBP.

Selective inhibition of the C5a chemotactic cofactor function of the vitamin D binding protein by 1,25(OH)2 vitamin D3

The Vitamin D binding protein (DBP) is a multifunctional plasma protein that can significantly enhance the chemotactic response to complement fragment C5a. The chemotactic cofactor function of DBP requires cell surface binding in order to mediate this process. The goal of this study was to investigate the effect of ligating DBP with its two primary physiological ligands, Vitamin D and G-actin, on both binding to neutrophils and the ability to enhance chemotaxis to C5a. There was no difference in neutrophil binding between of the holo (bound) forms versus the apo (unbound) form of radioiodinated DBP, indicating that the cell binding region of DBP is likely distinct from the Vitamin D sterol and G-actin binding sites. Likewise, G-actin, 25(OH)D3, and G-actin plus 25(OH)D3 bound to DBP did not alter its capacity to enhance chemotaxis toward C5a. However, the active form of Vitamin D (1,25(OH)2D3) completely eliminated the chemotactic cofactor function of DBP. Dose-response curves demonstrated that as little as 1pM 1,25(OH)2D3 significantly inhibited chemotaxis enhancement. Moreover, at physiological concentrations 1,25(OH)2D3 needs to be bound to DBP to mediate the inhibitory effect. Neutrophil chemotaxis to optimal concentrations of C5a, formyl peptide, CXCL8 or leukotriene B4 was not altered by 1,25(OH)2D3, indicating that the active vitamin does not have a global inhibitory effect on neutrophil chemotaxis. Finally, inhibition of cell surface alkaline phosphatase (AP) with sodium orthovanadate completely reversed the inhibitory effect of 1,25(OH)2D3. These results indicate that the cell binding and co-chemotactic functions of DBP are not altered when the protein binds G-actin and/or Vitamin D. Furthermore, the co-chemotactic signal from DBP can be eliminated or counteracted by 1,25(OH)2D3.

Identification of a Region in the Vitamin D-binding Protein that Mediates Its C5a Chemotactic Cofactor Function

The vitamin D-binding protein (DBP), also known as group-specific component or Gc-globulin, is a multifunctional plasma protein that can significantly enhance the leukocyte chemotactic activity to C5a and C5a des-Arg. DBP is a member of the albumin gene family and has a triple domain modular structure with extensive disulfide bonding that is characteristic of this protein family. The goal of this study was to identify a region in DBP that mediates the chemotactic cofactor function for C5a. Full-length and truncated versions of DBP (Gc-2 allele) were expressed in Escherichia coli using a glutathione S-transferase fusion protein expression system. The structure of the expressed proteins was confirmed by SDS-PAGE and immunoblotting, whereas protein function was verified by quantitating the binding of [(3)H]vitamin D. Dibutyryl cAMP-differentiated HL-60 cells were utilized to test purified natural DBP and recombinant expressed DBP (reDBP) for their ability to enhance chemotaxis and intracellular Ca(2+) flux to C5a. Natural and full-length reDBP (458 amino acid residues) as well as truncated reDBPs that contained the N-terminal domain I (domains I and II, residues 1-378; domain I, residues 1-191) significantly enhanced both cell movement and intracellular Ca(2+) concentrations in response to C5a. Progressive truncation of DBP domain I localized the chemotactic enhancing region between residues 126-175. Overlapping peptides corresponding to this region were synthesized, and results indicate that a 20-amino-acid sequence (residues 130-149, 5'-EAFRKDPKEYANQFMWEYST-3') in domain I of DBP is essential for its C5a chemotactic cofactor function.

Platelet-derived thrombospondin-1 is necessary for the vitamin D-binding protein (Gc-globulin) to function as a chemotactic cofactor for C5a

The chemotactic activity of C5a and C5a des Arg can be enhanced significantly by the vitamin D-binding protein (DBP), also known as Gc-globulin. DBP is a multifunctional 56-kDa plasma protein that binds and transports several diverse ligands. The objective of this study was to investigate the mechanisms by which DBP functions as a chemotactic cofactor for C5a using neutrophils and U937 cells transfected with the C5aR (U937-C5aR cells). The results demonstrate that U937-C5aR cells show C5a chemotactic enhancement only to DBP in serum, but, unlike mature neutrophils, this cell line cannot respond to DBP in plasma or to purified DBP. Analysis by SDS-PAGE and isoelectric focusing revealed no structural difference between DBP in serum compared with DBP in plasma. However, plasma supplemented with either serum, DBP-depleted serum, or activated platelet releasate provides a required factor and permits DBP to function as a chemotactic cofactor for C5a. Fractionation of activated platelet releasate revealed that the additional factor possessed the properties of thrombospondin-1 (TSP-1). Finally, purified TSP-1 alone could reproduce the effect of serum or platelet releasate, whereas Abs to TSP-1 could block these effects. These results provide clear evidence that TSP-1 is needed for DBP to function as a chemotactic cofactor for C5a.

Immune surveillance of mammary tissue by phagocytic cells

The leukocytes in milk consist of lymphocytes, neutrophil polymorphonuclear leukocytes (PMN) and macrophages. Lymphocytes together with antigen-presenting cells function in the generation of an effective immune response. Lymphocytes can be divided into two distinct subsets, T- and B-lymphocytes, that differ in function and protein products. The professional phagocytic cells of the bovine mammary gland are PMN and macrophages. In the normal mammary gland macrophages are the predominate cells which act as sentinels to invading mastitis causing pathogens. Once the invaders are detected, macrophages release chemical messengers called chemoattractants that cause the directed migration of PMN into the infection. Migration of neutrophils into mammary tissue provides the first immunological line of defense against bacteria that penetrate the physical barrier of the teat canal. However, their presence is like a double-edged sword. While the PMN are phagocytosing and destroying the invading pathogens, they inadvertently release chemicals which induces swelling of secretory epithelium cytoplasm, sloughing of secretory cells, and decreased secretory activity. Permanent scarring will result in a loss of milk production. Resident and newly migrated macrophages help reduce the damage to the epithelium by phagocytosing PMN that undergo programmed cell death through a process called apoptosis. Specific ligands on the neutrophil surface are required for directed migration and phagocytosis. In response to infection, freshly migrated leukocytes express greater numbers of cell surface receptors for immunoglobulins and complement and are more phagocytic than their counterparts in blood. However, phagocytic activity rapidly decreases with continued exposure to inhibitory factors such as milk fat globules and casein in mammary secretions. Compensatory hypertrophy in non-mastitic quarters partially compensates for lost milk production in diseased quarters. Advances in molecular biology are making available the tools, techniques, and products to study and modulate host-parasite interactions. For example the cloning and expression of proteins that bind endotoxin may provide ways of reducing damaging effects of endotoxin during acute coliform mastitis. The successful formation of bifunctional monoclonal antibodies for the targeted lysis of mastitis causing bacteria represents a new line of therapeutics for the control of mastitis in dairy cows.

Elastase controls the binding of the vitamin D-binding protein (Gc-globulin) to neutrophils: a potential role in the regulation of C5a co-chemotactic activity

The vitamin D-binding protein (DBP) binds to the plasma membranes of numerous cell types and mediates a diverse array of cellular functions. DBP bound to the surface of leukocytes serves as a co-chemotactic factor for C5a, significantly enhancing the chemotactic activity of pM concentrations of C5a. This study investigated the regulation of DBP binding to neutrophils as a possible key step in the process of chemotaxis enhancement to C5a. Using radioiodinated DBP as a probe, neutrophils released 70% of previously bound DBP into the extracellular media during a 60-min incubation at 37 degrees C. This was suppressed by serine protease inhibitors (PMSF, Pefabloc SC), but not by metallo- or thiol-protease inhibitors. DBP shed from neutrophils had no detectable alteration in its m.w., suggesting that a serine protease probably cleaves the DBP binding site, releasing DBP in an unaltered form. Cells treated with PMSF accumulate DBP vs time with over 90% of the protein localized to the plasma membrane. Purified neutrophil plasma membranes were used to screen a panel of protease inhibitors for their ability to suppress shedding of the DBP binding site. Only inhibitors to neutrophil elastase prevented the loss of membrane DBP-binding capacity. Moreover, treatment of intact neutrophils with elastase inhibitors prevented the generation of C5a co-chemotactic activity from DBP. These results indicate that steady state binding of DBP is essential for co-chemotactic activity, and further suggest that neutrophil elastase may play a critical role in the C5a co-chemotactic mechanism.

Effects of subclinical bovine paratuberculosis on in-vitro polymorphonuclear neutrophil migration

Migration of polymorphonuclear neutrophils (PMNs) [unstimulated or stimulated with zymosan-activated serum (ZAS)] from 18 cows was measured in a microwell filter assay. Of these animals, 10 were subclinically infected with Mycobacterium paratuberculosis and shown by culture to be excreting the organism in the faeces; the remaining eight were clinically normal and negative for M. paratuberculosis on faecal culture. PMN "net migration" (stimulated minus unstimulated cells) of the infected cows was significantly lower than that of the uninfected cows. Migration of unstimulated cells in the infected cows did not differ from that in the uninfected cows. It would therefore appear that the infection influenced only the migratory response of the ZAS-stimulated cells. 1999 Harcourt Publishers Ltd.

The effect of dexamethasone on some immunological parameters in cattle

Immunosuppression as a consequence of acute and chronic stress can increase the susceptibility of cattle to a range of infectious diseases. In order to develop a panel of immune function assays for investigating the effects of potential stressors on immune competence in cattle, the effect of treatment with short- and long-acting preparations of the synthetic glucocorticoid dexamethasone was examined. Short-acting dexamethasone (dexamethasone sodium phosphate 0.08 mg/kg) followed 37 h later by long-acting dexamethasone (dexamethasone-21 isonicotinate 0.25 mg/kg) was injected intramuscularly and blood was collected to assess immune functions at intervals over the subsequent 11 days from 6 treated and 6 control Hereford steers. Dexamethasone induced leukocytosis (neutrophilia, eosinopenia, lymphopenia, monocytosis), an increased neutrophil:lymphocyte ratio, an elevated percentage of CD4+ lymphocytes, a decreased total CD8+ lymphocyte count, decreased total and percentage WC1+ lymphocytes, an elevated percentage of IL-2 receptor alpha (IL-2Ralpha)+ lymphocytes, and an elevated percentage of B lymphocytes. In vitro chemotaxis of peripheral blood neutrophils to human C5a and ovine IL-8 was increased by dexamethasone treatment. Lymphocyte proliferation in the presence of phytohaemagglutinin, and serum concentrations of IgM, but not IgA or IgG1, were suppressed by dexamethasone treatment, whereas mitogen-induced production of interferon-gamma (IFN-gamma), neutrophil expression of CD18, neutrophil myeloperoxidase activity and natural killer (NK) cell activity were not influenced by dexamethasone treatment. The results indicate the potential for haematology and immune function assays to reflect elevated activity of the hypothalamic-pituitary-adrenocortical axis in cattle. Immunological parameters may thus provide a useful adjunct to cortisol and behavioural observations for assessing the impact of stress on the welfare of cattle.

Initial Characterization of the Vitamin D Binding Protein (Gc-Globulin) Binding Site on the Neutrophil Plasma Membrane: Evidence for a Chondroitin Sulfate Proteoglycan

The vitamin D binding protein (DBP) is a multifunctional plasma protein that can modulate certain immune and inflammatory responses. The diverse cellular functions of DBP appear to require cell surface binding to mediate these processes. Numerous reports have detected DBP bound to the surface of several cell types and would support the concept of a cell surface binding site for DBP. However, direct evidence for such a molecule has been lacking and essentially nothing is known about its basic biochemical properties. In the present study, radioiodinated DBP was used as a probe to characterize biochemically the neutrophil DBP binding site. Radiolabeled DBP binds to and remains associated with the plasma membrane and is not degraded. Quantitation of DBP binding to either intact cells or purified plasma membranes showed nonsaturable (linear) binding with positive cooperativity, possibly suggesting DBP oligomer formation. Solubilization of cell bound 125I-DBP with various nonionic and zwitterionic detergents demonstrated that DBP binds to a membrane macromolecule that partitions to the detergent insoluble fraction. Moreover, this molecule does not associate with the cytoskeleton. Cross-linking of radiolabeled DBP bound to plasma membranes increased the amount of protein that partitioned to the insoluble fraction, and analysis of these complexes by SDS-PAGE revealed that they may be very large since they did not enter the gel. Finally, treatment of plasma membranes with either proteases or chondroitinase ABC completely abrogated membrane binding of DBP, suggesting that the protein binds to a chondroitin sulfate proteoglycan.

Interaction of dexamethasone and Salmonella enteritidis immune lymphokines on Salmonella enteritidis organ invasion and in vitro polymorphonuclear leukocyte function

We used an anti-inflammatory dose of dexamethasone (DEX) and Salmonella enteritidis (SE)-immune lymphokines (ILK) followed by oral SE challenge to chicks to determine the effects of these treatments on SE organ invasion and in vitro function of PMNs derived from peripheral blood. Endpoints included percent protection against SE organ invasion, numbers of peripheral blood PMNs, and in vitro PMN adherence, chemotaxis, and SE killing. SE organ invasion was significantly reduced in chicks treated with either ILK alone or DEX + ILK compared to controls. Chicks treated with either DEX alone or DEX + ILK responded with a significant increase in numbers of peripheral blood PMNs as compared to controls, while numbers of PMNs in the peripheral blood from chicks treated with ILK alone were not significantly increased. PMN adherence and percent SE killing by PMNs derived from chicks treated with either ILK alone or DEX + ILK were significantly increased compared to controls. Chemotaxis of PMNs derived from chicks treated with either ILK alone or DEX alone significantly increased 2-fold over control levels. Interestingly, chemotaxis of PMNs derived from chicks that received DEX + ILK was similar to controls. Generally, ILK abated the anti-inflammatory effects of DEX on PMNs in these assays, except for chemotaxis. We interpret these data to suggest that ILK may confer protection to chicks against the early phase of SE organ invasion by inducing an inflammatory response predominated by activated PMNs.

Influence of anti-inflammatory drugs on adhesion of neutrophils to endothelial cells cultured on microcarriers: a novel in vitro system as an alternative to animal experimentation

Pharmacological control of inflammation by steroidal (SAIDs) and nonsteroidal (NSAIDs) antiinflammatory drugs is of substantial clinical importance. To reduce the number of animals used in pharmacological and toxicological evaluation of these drugs we developed a novel assay to determine adhesion of bovine neutrophils (PMN) to bovine aortic endothelial cells (BAEC) cultured on microcarriers in a flow-through system. Pretreatment of BAEC with thrombin (10(-7)-10(-4) M) led to a dose-dependent increase of PMN-adhesion (10(-6)-10(-4) M:P < 0.05); platelet-activating factor (10(-9) M) and 1:200 diluted zymosan-activated serum (ZAS) had similar effects (P < 0.001). Pretreatment of PMN with SAIDs (50.9 and 509 microM dexamethasone, 12.2 and 24.4 microM flumethasone) did inhibit adhesion to ZAS-treated BAEC dose-dependently. Pretreatment of PMN with NSAIDs had a less consistent influence on adhesion to ZAS-stimulated BAEC. While phenylbutazone (0.33 and 3.3 mM), diclofenac (0.392 and 0.574 mM), indomethacine (0.436 and 0.872 mM), and acetylsalicylic acid (3.47 and 16.94 mM) induced dose-dependent inhibition of PMN-adhesion to ZAS-treated BAEC, piroxicam (0.377 and 0.754 mM) inhibited PMN-adhesion strongly (P < 0.001) but not dose-dependently, and ketoprofene (0.614 and 1.228 mM) had no effect on PMN-adhesion. The method presented here is efficient for evaluating the pharmacological modulation of PMN interaction with endothelial cells, and useful for studying further aspects of endothelial cell biology.

Leukocyte functions of young dairy calves fed milk replacers supplemented with vitamins A and E

Holstein calves (n = 44) were fed milk replacers from d 3 to 45 with low or high concentrations of vitamin A (7000 or 87,000 IU/kg) and vitamin E (11.2 or 57 IU/kg) to examine the influence of vitamin concentrations on vitamin bioavailability and leukocyte functions. Concentrations of alpha-tocopherol in plasma reflected increased vitamin E but were unaffected by increased vitamin A. Plasma retinol concentrations were greatest with high supplementation of vitamins A and E at wk 3; however, at wk 6, plasma of calves fed high vitamin A and low vitamin E contained the most retinol. Increased supplementation of vitamin A improved fecal consistency compared with that for calves fed the low vitamin A diet at wk 3 and 4. At wk 3, calves that received increased supplementation of vitamins E and A had enhanced neutrophil bactericidal activity compared with that of calves with increased individual vitamins. Lymphocyte DNA synthesis and chemotactic index were unaffected by dietary treatments. Results indicate that increased vitamin A in milk replacer did not affect plasma vitamin E concentrations, benefited fecal scores regardless of vitamin E concentrations, but was only beneficial to bactericidal activity of neutrophils in conjunction with increased vitamin E.

Comparative in vitro phagocytosis and F-actin polymerization of bovine neonatal neutrophils

Analysis of neonatal neutrophil (PMN) functions should help to reveal factors which could contribute to the impaired host defense system of neonates. We analysed functional parameters of PMN from newborn calves (N-PMN) and adult bovines (A-PMN): cellular volume and F-actin content upon stimulation with complement factors, by cytofluorometry and phagocytosis of E. coli 78:80B with a colorimetric assay. Polymerization of F-actin was rapid in both N- and A-PMN, but reached higher levels in N-PMN. N-PMN are significantly smaller than A-PMN throughout the whole activation time. Percentage of phagocytosing PMN, the rate of phagocytosis, and the rate of killing are similar between A- and N-PMN after opsonization of bacteria with adult serum (AS). Opsonization with newborn serum (NS) reduced all three examined parameters: in A-PMN more (P < 0.001) than in N-PMN (P < 0.05). However, when phagocytosis was compared following age-matched opsonization (N-PMN and NS; A-PMN and AS), N-PMN phagocytosed less (P < 0.001) bacteria per PMN than A-PMN. Additionally, steroidal (dexamethasone) and non-steroidal (phenylbutazone) anti-inflammatory drugs inhibited phagocytosis by N-PMN less than by A-PMN. Higher relative F-actin content of N-PMN can be correlated with the documented functional hyperactivity of bovine N-PMN. However, the exaggerated impairment of phagocytosis in calves observed after age-matched opsonization of bacteria could potentially indicate a specific host defence defect.

Role of the neutrophil leucocyte in the local and systemic reactions during experimentally induced E. coli mastitis in cows immediately after calving

Mammary leucocytes are the major contributors to natural defence against mastitis after a microorganism has entered the gland. This paper reviews the role of the neutrophil granulocyte during acute coliform mastitis in cows in the periparturient period. Qualitative and quantitative aspects of several neutrophil cell functions before and during experimentally induced infections are briefly discussed.

Vitamin concentration and function of leukocytes from dairy calves supplemented with vitamin A, vitamin E, and beta-carotene in vitro

Blood neutrophils and pulmonary alveolar macrophages, isolated from calves at 3 and 6 wk of age, were cultured in medium without added vitamins or supplemented with 100 micrograms/dl of vitamin A, 1000 micrograms/dl of vitamin E, 100 micrograms/dl of vitamin A plus 1000 micrograms/dl of vitamin E, or .25 micrograms/dl of beta-carotene plus 1000 micrograms/dl of vitamin E. Macrophage bactericidal activity improved with supplementation of vitamins A plus E compared with supplementation of beta-carotene plus E or vitamin E at wk 3. Neutrophil bactericidal activity decreased with all vitamin E treatments at wk 3 and with vitamins E or A plus E at wk 6. Neutrophil phagocytosis improved at wk 3 with supplementations of vitamins A, E, and A plus E. The chemotactic index improved with beta-carotene and vitamin E compared with vitamin E alone at wk 3 and at wk 6 with vitamin E compared with vitamin A and control treatments. Retinol content of neutrophils varied at wk 3, but, by wk 6, cells supplemented with vitamins A, E, or A plus E had greater retinol concentrations than control cells. Neutrophil alpha-tocopherol concentrations at wk 3 increased from those of controls with supplementation of vitamin E or beta-carotene and vitamin E, but, at wk 6, vitamin E-supplemented cells were different only from vitamin A-supplemented cells. These data suggest that optimal plasma concentrations of vitamins A and E exist for leukocyte function.

In vitro and in vivo activity of human interleukin-8 in dogs

Interleukin-8 (IL-8), a proinflammatory cytokine produced by human monocytes, fibroblasts, and endothelial and epithelial cells, is effective not only on cells and tissues of human beings but also on those of several animal species. We investigated the importance of recombinant human IL-8 for the activation of canine neutrophils in vitro and its potential for inducing inflammation in vivo. Shape change (10(-9)-10(-7) M IL-8) and chemotaxis (10(-10)-10(-6) M IL-8) assays were used to determine the activation of canine neutrophils in vitro. Chemotaxis was induced by IL-8 at doses > 10(-8) M with a maximum response at 10(-6) M. A rapid shape change of comparable intensity was elicited by 10(-9)-10(-7) M IL-8. Thirty minutes after intradermal injection of 10(-9) moles of IL-8, emigration of neutrophils could be observed and became more intense at 60 minutes and 240 minutes, respectively. Zymosan-activated canine plasma, which served as a positive control, induced a rapid, massive, and more diffuse neutrophil accumulation, whereas the reaction after IL-8 was weaker but still significant. The neutrophil accumulation after IL-8 was preferentially located in perivenular areas of the deep dermis. Recombinant human IL-8 is capable of activating canine neutrophils in vitro and is able to generate significant neutrophil accumulation in dog skin. Its activity is lower than that in human, rabbit, and rat systems.

Effects of certain inflammatory mediators on bovine neutrophil migration in vivo and in vitro

Migration of bovine neutrophils towards endotoxin, recombinant bovine interleukin-1 beta (rBoIL-1 beta), recombinant human tumor necrosis factor-alpha (rhTNF-alpha), platelet-activating factor (PAF), complement factor C5a, leukotriene B4 (LTB4), and recombinant human interleukin-8 (rhIL-8) was studied in vivo, using the teat cistern model, and in vitro using the modified Boyden chamber method. Infusion of endotoxin, rBoIL-1 beta, rhTNF-alpha, PAF, or C5a into the teat cistern induced significant accumulation of leukocytes, mainly neutrophils, during the sampling period. Endotoxin was, on a molar basis, the most potent inducer of cell accumulation in vivo, followed by rBoIL-1 beta, while C5a, PAF and rhTNF-alpha were less potent. No significant cell accumulation was observed after infusion of LTB4 or rhIL-8. A significant migration of cells into the teat cistern was first observed 2 h after the infusion of endotoxin or rBoIL-1 beta, the rBoIL-1 beta-induced response started somewhat earlier. The first significant cell accumulation after infusion of PAF or C5a was observed already 1.5 h post infusion. The largest numbers of cells were reached 2.5-4.5 h after the infusion of endotoxin, rBoIL-1 beta, rhTNF-alpha, PAF or C5a. In vitro, significant migration of bovine blood neutrophils was observed towards C5a or rhIL-8, and to a lower extent towards LTB4, while no chemotactic response to endotoxin, rBoIL-1 beta, rhTNF-alpha, and PAF was observed. Possible roles of the different substances as inducers of neutrophil migration into the bovine teat are discussed.

A study of the development of endotoxin-induced inflammation in the bovine teat

Endotoxin-induced local inflammation was studied by frequent samplings in a bovine teat cistern model, which provides a unique possibility for in vivo studies of reactions in the teat without interference from the mammary gland. A rapid inflammatory response of rather short duration was elicited after endotoxin administration. An initial increase in the concentrations of bovine serum albumin and N-acetyl-beta-D-glucosaminidase, indicating a disturbance in the epithelial integrity, was observed between 1 and 1.5 h post infusion (p.i.). Approximately 0.5 h later, the first influx of leukocytes, mainly neutrophils, appeared. The neutrophils tended to enter the teat cistern in several peaks occurring between 2.5 and 5 h p.i. The sampling procedure decreased the accumulation of cells by approximately 40%, which was probably due to the removal of inflammatory mediators at an early stage. The parallel use of 2 teats instead of 1 had no major influence on the inflammatory process. This teat cistern model and the experimental procedure used should be suitable for further studies of the development of local inflammation.

Bovine herpesvirus-1-induced pharyngeal tonsil lesions in neonatal and weanling calves

The potential involvement of the pharyngeal tonsil in the pathogenesis of bovine herpesvirus-1 (BHV-1) infection was examined in neonatal and weanling calves infected by intranasal aerosol. Calves were monitored from days 1 to 5, and on day 6 (neonates) or 8 (weanlings) and, in a second trial at day 4.5, by histology, electron microscopy, immunocytochemistry and virus isolation. Mucosal lesions of neonates were similar to, but less extensive than, those of weanling calves. Loss of microvilli and goblet cells, with minimal epithelial erosions as early as day 1, progressed to necrosis of epithelium and adjacent lymphoid tissue, and leucocyte exudation. Lesions and clinical disease were progressive up to and including day 6 in neonates, but resolving in weanlings on days 5 and 8. By transmission electron microscopy, the physical characteristics of the phagocytic cells appeared similar in both age groups, and viral replication was not identified in leucocytes. Virus was isolated from, or found by immunocytochemistry in, the pharyngeal tonsil of all calves examined, except for two weanlings on days 1 and 8. Virus as detected by immunocytochemistry was restricted to epithelium and superficial lymphoid tissue in neonates, but was found in deep lymphoid tissue around germinal centres in weanlings. The study showed that the pharyngeal tonsil is readily infected with BHV-1 and may be an important lymphoid tissue for early anti-viral responses. The delayed inflammatory response and reduced viral clearance may contribute to the increased susceptibility of neonatal calves to fatal BHV-1 infections.

In vitro aggregation of bovine neonatal neutrophils. A comparative study with adult cattle

Deficient in vitro functions of neonatal neutrophils have been reported in various species. They may be functionally related to the well-known susceptibility of newborn individuals to microbial infections. To evaluate an early step in the sequence of neutrophil activation, neutrophils from adult cows (A-PMN) and newborn calves (N-PMN) were stimulated with zymosan-activated plasma (ZAP) or with the lipid mediator platelet-activating factor (PAF): Aggregation was recorded kinetically in a standard aggregometer and measured quantitatively as the area under the aggregation curve (AUAC). The mean +/- SEM of the AUAC of the first 2.5 min of the reaction induced with ZAP was similar in N-PMN and A-PMN. However, N-PMN deaggregated only partially, whereas A-PMN deaggregated almost completely (P less than 0.05). This may indicate a mechanism of microvascular sequestration in vivo with the potential to inhibit chemotaxis. PAF (10(-5)-10(-10) M) aggregated N- and A-PMNs similarly and dose-dependently with a maximal reaction at 10(-6) M. Inhibition of aggregation induced by 10(-6) M PAF was evaluated by preincubation with four antiinflammatory drugs: dexamethasone (Dex: 5.1, 51.0, 510.0 microM), flumethasone (Flu: 12.2 and 122.0 microM), phenylbutazone (PB: 0.33 and 3.3 mM), and flunixin meglumine (Flxin: 51 and 510 microM). Dex and Flu each inhibited (P less than 0.05) PAF-induced N-PMN aggregation at the highest dose, and A-PMN aggregation at the two higher doses. PB and Flxin each inhibited aggregation of N- and A-PMNs at all doses used. We compared the inhibition rate in both age groups and could demonstrate that Dex, Flu, and Flxin each at the highest dose, and PB at all doses used, inhibited PAF-induced aggregation less (P less than 0.05) in N-PMNs than in A-PMNs. These functional differences indicate hyperirritability of N-PMNs, and they need further elucidation to help understand mechanisms of increased neonatal susceptibility.