Review of neutrophil adherence, chemotaxis, phagocytosis and killing

Immunotoxicity of microplastics in fish

Plastic waste degrades slowly in aquatic environments, transforming into microplastics (MPs) and nanoplastics (NPs), which are subsequently ingested by fish and other aquatic organisms, causing both physical blockages and chemical toxicity. The fish immune system serves as a crucial defense against viruses and pollutants present in water. It is imperative to comprehend the detrimental effects of MPs on the fish immune system and conduct further research on immunological assessments. In this paper, the immune response and immunotoxicity of MPs and its combination with environmental pollutants on fish were reviewed. MPs not only inflict physical harm on the natural defense barriers like fish gills and vital immune organs such as the liver and intestinal tract but also penetrate cells, disrupting intracellular signaling pathways, altering the levels of immune cytokines and gene expression, perturbing immune homeostasis, and ultimately compromising specific immunity. Initially, fish exposed to MPs recruit a significant number of macrophages and T cells while activating lysosomes. Over time, this exposure leads to apoptosis of immune cells, a decline in lysosomal degradation capacity, lysosomal activity, and complement levels. MPs possess a small specific surface area and can efficiently bind with heavy metals, organic pollutants, and viruses, enhancing immune responses. Hence, there is a need for comprehensive studies on the shape, size, additives released from MPs, along with their immunotoxic effects and mechanisms in conjunction with other pollutants and viruses. These studies aim to solidify existing knowledge and delineate future research directions concerning the immunotoxicity of MPs on fish, which has implications for human health.

LDLa containing C-type lectin mediates phagocytosis of V.anguillarum and regulates immune effector genes in shrimp

C-type lectins (CTLs) function as pattern recognition receptors (PRRs) by recognizing invading microorganisms, thereby triggering downstream immune events against infected pathogens. In this study, a novel CTL containing a low-density lipoprotein receptor class A (LDLa) domain was obtained from Litopenaeus vannamei, designed as LvLDLalec. Stimulation by the bacterial pathogen Vibrio anguillarum (V. anguillarum) resulted in remarkable up-regulation of LvLDLalec, as well as release of LvLDLalec into hemolymph. The rLvLDLalec protein possessed broad-spectrum bacterial binding and agglutinating activities, as well as hemocyte attachment ability. Importantly, LvLDLalec facilitated the bacterial clearance in shrimp hemolymph and protected shrimp from bacterial infection. Further studies revealed that LvLDLalec promoted hemocytes phagocytosis against V. anguillarum and lysosomes were involved in the process. Meanwhile, LvLDLalec participated in humoral immunity through activating and inducing nuclear translocation of Dorsal to regulate phagocytosis-related genes and antimicrobial peptides (AMPs) genes, thereby accelerated the removal of invading pathogens in vivo and improved the survival rate of L. vannamei. These results unveil that LvLDLalec serves as a PRR participate in cellular and humoral immunity exerting opsonin activity to play vital roles in the immune regulatory system of L. vannamei.

A single-CRD C-type lectin from Haliotis discus hannai acts as pattern recognition receptor enhancing hemocytes opsonization

C-type lectins (CTLs), as a member of the Ca²⁺-dependent carbohydrate recognition protein superfamily, play multiple roles in non-self recognition and the elimination of invading pathogens. In this study, a C-type lectin was identified and characterized from the Pacific abalone Haliotis discus hannai (designed as HdClec), and its open reading frame (ORF) encoded a polypeptide of 163 amino acids containing a typical signal peptide and only one carbohydrate-recognition domain (CRD). The deduced amino acid sequence of CRD in HdClec shared identities ranging from 22.4% to 39.8% with that of other identified CRDs of CTLs. A novel NPN motif was found in Ca²⁺-binding site 2 of HdClec. The mRNA transcripts of HdClec were detectable in all the examined tissues of non-stimulated abalones, with the highest expression in hepatopancreas (224.13-fold of that in gills). The expression of HdClec mRNA in hemocytes was significantly up-regulated after Vibrio harveyi challenge. Recombinant HdClec protein (rHdClec) could bind lipopolysaccharide (LPS) and peptidoglycan (PGN) in vitro in the presence of Ca²⁺. Coinciding with the PAMPs binding assay, rHdClec displayed broad agglutination activities towards Gram-negative bacteria V. splendidus, V. anguillarum, V. parahaemolyticus, V. harveyi, Escherichia coli, and Gram-positive bacteria Micrococcus luteus. Moreover, rHdClec could significantly elicit the chemotactic response of hemocytes in vitro. And the phagocytosis and encapsulation ability of hemocytes could be significantly enhanced by rHdClec. All these results showed that HdClec could function as pattern recognition receptors (PRRs) and further enhance the opsonization of hemocytes, which might play a crucial role in the innate immune responses of Pacific abalone.

Ecotoxicological and physiological risks of microplastics on fish and their possible mitigation measures

Microplastics (MPs) are widely distributed and extensively found within marine ecosystems, and approximately 8 million tons of plastics are being dumped into the sea annually. Once reached the marine environment, plastics tend to get fragmented into smaller particles through photo-degradation, mechanical and biological processes. These MPs have raised concerns globally due to their potential toxic impacts on a wide variety of aquatic fauna and humans. Ingested microplastics can cause severe health implications in fishes, including reduced feeding intensity, improper gill functioning, immuno-suppression, and compromised reproducibility. Several studies were also conducted to scrutinize MPs trophic transfer through the food chain from primary producers to top predators and their bioaccumulation. This paper briefly summarizes all the possible sources, routes, bioavailability, trophic transfer, and consequences of microplastics in fishes. The review article also intended to highlight various mitigation strategies like implementing Four R's concept (refuse, reduce, reuse, and recycle), integrated strategies, ban on single-use plastics, use bioplastics, and create behavioural changes with public awareness.

Microplastic pollution as a grand challenge in marine research: A closer look at their adverse impacts on the immune and reproductive systems

Microplastic (MP) pollution of the marine environment is now a growing global concern posing a threat to a variety of species through the ingestion and transfer within food webs. This is considered a potential toxicological threat to marine species due to the chemical additives used to make many plastic products, or the persistent organic pollutants that may accumulate on them while residing in the environment. While the presence of MPs in the marine environment is widely documented, there are no other review articles providing a summary of published effect studies of MPs on the immune and reproductive systems of marine species. This manuscript reviews reproductive and immune-system changes in response to MPs in 7 and 9 species, respectively. Some species such as Mytilus galloprovincialis and oyster Crassostrea gigas were investigated in multiple papers. Most studies have been conducted on invertebrates, and only 3 studies have been performed on vertebrates, with exposure times ranging between 30 min and 60 days. A review of the literature revealed that the most common MPs types studied in relation to adverse impacts on immune system and reproductive success in marine species were polystyrene (PS) and polyethylene (PE). The immune system's responses to MPs exposure varied depending on the species, with altered organismal defense mechanisms and neutrophil function observed in fish and changes in lysosomal membrane stability and apoptotic-like nuclear alterations in phagocytes reported in invertebrate species. Reproductive responses to MPs exposure, varied depending on species, but included significant reduction in gamete and oocyte quality, fecundity, sperm swimming speed, and quality of offspring. The lack of published data means that developing a clear understanding of the impact across taxonomic groups with different feeding and behavioral traits is often difficult. Further work is required to better understand the risk MPs pose to the immune and reproductive systems of marine species in order to fully evaluate the impact these ubiquitous pollutants are having on marine ecosystems and the associated goods and services they provide.

Microfluidic Devices Developed for and Inspired by Thermotaxis and Chemotaxis

Taxis has been reported in many cells and microorganisms, due to their tendency to migrate toward favorable physical situations and avoid damage and death. Thermotaxis and chemotaxis are two of the major types of taxis that naturally occur on a daily basis. Understanding the details of the thermo- and chemotactic behavioral response of cells and microorganisms is necessary to reveal the body function, diagnosing diseases and developing therapeutic treatments. Considering the length-scale and range of effectiveness of these phenomena, advances in microfluidics have facilitated taxis experiments and enhanced the precision of controlling and capturing microscale samples. Microfabrication of fluidic chips could bridge the gap between in vitro and in situ biological assays, specifically in taxis experiments. Numerous efforts have been made to develop, fabricate and implement novel microchips to conduct taxis experiments and increase the accuracy of the results. The concepts originated from thermo- and chemotaxis, inspired novel ideas applicable to microfluidics as well, more specifically, thermocapillarity and chemocapillarity (or solutocapillarity) for the manipulation of single- and multi-phase fluid flows in microscale and fluidic control elements such as valves, pumps, mixers, traps, etc. This paper starts with a brief biological overview of the concept of thermo- and chemotaxis followed by the most recent developments in microchips used for thermo- and chemotaxis experiments. The last section of this review focuses on the microfluidic devices inspired by the concept of thermo- and chemotaxis. Various microfluidic devices that have either been used for, or inspired by thermo- and chemotaxis are reviewed categorically.

Polycarbonate and polystyrene nanoplastic particles act as stressors to the innate immune system of fathead minnow (Pimephales promelas)

Water pollution with large-scale and small-scale plastic litter is an area of growing concern. Macro-plastic litter is a well-known threat to aquatic wildlife; however, the effects of micro-sized and nano-sized plastic particles on the health of organisms are not well understood. Small-scale plastic particles can easily be ingested by various aquatic organisms and potentially interfere with their immune system; therefore, the authors used a freshwater fish species as a model organism for nanoplastic exposure. Characterization of polystyrene (41.0 nm) and polycarbonate (158.7 nm) nanoplastic particles (PSNPs and PCNPs, respectively) in plasma was performed, and the effects of PSNPs and PCNPs on the innate immune system of fathead minnow were investigated. In vitro effects of PSNPs and PCNPs on neutrophil function were determined using a battery of neutrophil function assays. Exposure of neutrophils to PSNPs or PCNPs caused significant increases in degranulation of primary granules and neutrophil extracellular trap release compared to a nontreated control, whereas oxidative burst was less affected. The present study outlines the stress response of the cellular component of fish innate immune system to polystyrene and polycarbonate nanoparticles/aggregates and indicates their potential to interfere with disease resistance in fish populations. Environ Toxicol Chem 2016;35:3093-3100. © 2016 SETAC.

Prognostic value of neutrophil-to-lymphocyte ratio in pulmonary arterial hypertension

OBJECTIVE

To evaluate the prognostic value of baseline neutrophil-to-lymphocyte ratio (NLR) in the prediction of long-term mortality in patients with pulmonary arterial hypertension (PAH).

METHODS

This prospective study recorded NLR during initial diagnostic right-sided cardiac catheterization in adult patients with PAH. Demographic, clinical, laboratory and haemodynamic variables were compared by NLR tertile. Univariate and multivariate Cox regression analyses were used to determine whether NLR was independently associated with mortality.

RESULTS

Adults with PAH (n = 101) were followed-up for mean ± SD 36.8 ± 23.6 months. The number of deaths, New York Heart Association functional capacity (NYHA FC), levels of brain natriuretic peptide (BNP) or C-reactive protein (CRP) and presence of pericardial effusion increased as the NLR tertile increased, but haemoglobin and tricuspid plane annular systolic excursion (TAPSE) decreased. On univariate analysis, high NLR values were associated with mortality, but on multivariate analysis, NLR did not remain an independent predictor of mortality. Baseline NYHA FC, TAPSE, BNP level and pericardial effusion were independent predictors of mortality.

CONCLUSIONS

NLR was correlated with important prognostic markers in PAH such as NYHA FC, BNP and TAPSE. This simple marker may be useful in the assessment of disease severity in patients with PAH.

The prognostic utility of degenerative left shifts in dogs

BACKGROUND

A degenerative left shift (DLS) in dogs is reported to be a poor prognostic indicator, but no studies have been reported to verify this claim.

HYPOTHESIS/OBJECTIVES

To characterize the canine population affected by DLS and to determine if the presence and severity of the DLS are associated with increased risk of euthanasia or death.

ANIMALS

Three-hundred and nineteen dogs with DLS (cases) and 918 dogs without DLS (controls) presented to the University of California, Davis Veterinary Medical Teaching Hospital between April 1, 1995 and April 1, 2010.

METHODS

Retrospective case-control study. All cases had a CBC performed within 24 hours of presentation that showed an immature neutrophil count higher than the mature neutrophil count. Controls were matched by year of presentation and primary diagnosis. Survival analysis was used to determine the risk of death or euthanasia associated with DLS and other potential predictors.

RESULTS

Half of cases versus 76% of controls were alive at discharge. Median in-hospital survival time was 7 days for cases and 13 days for controls. DLS was a significant predictor of death or euthanasia in both univariate and multivariate analysis (hazard ratio, HR, 1.9; 95% CI 1.54-2.34).

CONCLUSIONS AND CLINICAL IMPORTANCE

DLS in dogs is associated with an increased risk of death or euthanasia. This finding, however, varies with disease diagnosis and should be interpreted in light of the individual patient.

Disease resistance and health parameters of growth-hormone transgenic and wild-type coho salmon, Oncorhynchus kisutch

To extend previous findings regarding fish health and disease susceptibility of growth-enhanced fish, hematological and immunological parameters have been compared between growth hormone (GH) transgenic and wild-type non-transgenic coho salmon (Oncorhynchus kisutch). Compared to non-transgenic coho salmon, transgenic fish had significantly higher hematocrit (Hct), hemoglobin (Hb), mean cellular hemoglobin (MCH), mean cellular volume (MCV), and erythrocyte numbers, and lower white cell numbers. In addition, resistance to the bacterial pathogen Aeromonas salmonicida (causal agent of furunculosis) has been assessed between the strains. Higher susceptibility of transgenic fish to this disease challenge was observed in two separate year classes of fish. The present findings provide fundamental knowledge of the disease resistance on GH enhanced transgenic coho salmon, which is of importance for assessing the fitness of transgenic strains for environmental risk assessments, and for improving our understanding effects of growth modification on basic immune functions.

Effect of tricainemethanesulfonate (MS222), clove oil and electro-anaesthesia on respiratory burst activity in whole blood and serum alternative complement response in rainbow trout (Oncorhynchus mykiss), during the narcosis stage

There is a little available information on the suppressive effect of anaesthesia on immune response in fish, especially electro-anaesthesia. In the present study, two anaesthetics, MS222 (50 ppm), clove oil (25 ppm), and electro-anaesthesia were tested in rainbow trout (Oncorhynchus mykiss) during the narcosis stage in order to observe their effects on the innate immune system. The results showed that electro-anaesthesia reduces light emission in chemiluminescence assay both 1 and 24 h post anaesthesia. Clove oil and MS222 decreased light emission 24 h post anaesthesia. In addition, clove oil, MS222 and electro-anaesthesia had no effect on alternative complement (ACH50) response. From the perspective of aquaculture practice, these data show that the type of anaesthesia should be taken into account to avoid possible immunosuppression in rainbow trout.

Effects of nanosized titanium dioxide on innate immune system of fathead minnow (Pimephales promelas Rafinesque, 1820)

Effects of nanosized (<100 nm) titanium dioxide (TiO(2)) particles on fish neutrophils and immune gene expression was investigated using the fathead minnow (Pimpehales promelas). Expanded use of TiO(2) in the cosmetic industry has increased the potential exposure risk to aquatic ecosystems and human health. Effects of nano-TiO(2) on neutrophil function of the fathead minnow was investigated using oxidative burst, neutrophil extracellular traps (NETs) release and degranulation of primary granules. The innate immune gene expression was determined with quantitative PCR (qPCR). Application of 0.1 μg mL(-1) of nano-TiO(2) in vitro stimulated oxidative burst and NET release. Intraperitoneal injection of 10 μg g(-1) of nano-TiO(2) caused a significant decrease in oxidative burst, NETs release and degranulation (21%; 11%; and 30%, decrease, respectively). Fish exposed to nano-TiO(2) for 48 h in vivo had significantly increased expression of interleukin 11, macrophage stimulating factor 1, and neutrophil cytosolic factor 2 (4; 2.5; and 2 fold increase, respectively). Nano-TiO(2) has potential to interfere with the evolutionary conserved innate immune system responses, as evidenced with observed changes in gene expression and neutrophil function. This finding encourages the use of fish models in the studies of nanoparticle immunotoxicity. The lowest significant response concentration studied in vitro is four times greater than the estimated environmental concentration for TiO(2) (0.025 μg mL(-1)) causing concern about potential impact of nano-TiO(2) on aquatic animals and ecosystems.

Hydroxylated fullerenes inhibit neutrophil function in fathead minnow (Pimephales promelas Rafinesque, 1820)

Hydroxylated fullerenes act as potent inhibitors of cytochrome P450-dependent monooxygenases, and are reported to be very strong antioxidants quenching reactive oxygen species (ROS) production. Effects of nanosized hydroxylated fullerenes on fish neutrophil function and immune gene transcription was investigated using fathead minnow (Pimephales promelas). Neutrophil function assays were used to determine the effects of fullerene exposure in vitro and in vivo on oxidative burst, degranulation and extracellular trap (NETs) release, and the innate immune gene transcription was determined with quantitative PCR (qPCR). Application of fullerenes (0.2-200 microgmL(-1)in vitro) caused concentration dependent inhibition of oxidative burst and suppressed the release of NETs and degranulation of primary granules (up to 70, 40, and 50% reduction in activity compared to non-treated control, respectively). Transcription of interleukin 11 and myeloperoxidase genes was significantly increased and transcription of elastase 2 gene was significantly decreased in fish exposed to hydroxylated fullerenes for 48h in vivo (12 and 3 fold increase, and 5 fold decrease, respectively). Observed changes in gene transcription and neutrophil function indicate potential for hydroxylated fullerenes to interfere with the evolutionary conserved innate immune system responses and encourages the use of fish models in studies of nanoparticle immunotoxicity.

Dietary administration of Zooshikella sp. enhance the innate immune response and disease resistance of Paralichthys olivaceus against Sreptococcus iniae

We report the growth, innate immune response, and disease resistance in olive flounder (Paralichthys olivaceus) challenged with Streptococcus iniae after feeding with diet enriched with Zooshikella sp. strain JE-34 three different concentration i.e. Low (3.4 x 10(4), n = 50), medium (3.5 x 10(6), n = 50), and high (3.4 x 10(8), n = 50) cfu ml(-1) supplemented diets, the changes were monitored on weeks 1, 2, 4, 8, 12, and 16. With all diets the innate immune parameters, such as superoxide anion production, phagocytic and lysozyme activity were not enhanced on week 1 and 4. On the other hand, all tested immune parameters in the treated groups significantly enhanced after 8th week; the weight gain significantly increased after 4th week in fish fed with enriched diets. The mortality in olive flounder after administration with high concentration diet showed 25%. With low and medium enriched diets the mortality was 40% and 35%, respectively. In the infected untreated group mortality was 85% while there was no mortality in the control group. The results suggested that Zooshikella sp. strain JE-34 enriched diets could be used to enhance the innate immune response and disease resistance of P. olivaceus against S. iniae.

Zebrafish (Danio rerio) whole kidney assays to measure neutrophil extracellular trap release and degranulation of primary granules

The zebrafish (Danio rerio) is an excellent model system for studies in developmental biology, genetics, and toxicology, and is increasingly gaining importance in the field of immunology. The use of whole zebrafish kidneys as source of neutrophils for degranulation assays and detection of neutrophil extracellular traps is described for the first time. Neutrophils from zebrafish kidneys released neutrophil extracellular traps (NETs) and myeloperoxidase (MPO) upon stimulation with calcium ionophore, phorbol myristate acetate, and beta-glucan. Immunocytochemical study of zebrafish kidney cells revealed that NETs are made of DNA fibers associated with neutrophil granular proteins, but not with cytoskeleton. Rapid, direct MPO and extracellular DNA detection assays were developed to quantify NET release and degranulation of neutrophil primary granules from whole zebrafish kidneys. The assays were used to measure the effects of acute crowding and handling stress on neutrophils, and to examine the potential for use of zebrafish whole kidney assays in evaluation of neutrophil function under different conditions in vivo. The whole kidney NET release and degranulation assays are quantitative, can rapidly measure a large number of samples, and are capable of detecting inhibition of neutrophil activity in stressed fish, overcoming the limitations that prevented use of zebrafish in the investigations of cellular innate immune function. The assays can be used as a new research model to study effects of stress, immunomodulators, toxicants, and diseases on fish neutrophil biology.

A rapid, direct assay to measure degranulation of primary granules in neutrophils from kidney of fathead minnow (Pimephales promelas Rafinesque, 1820)

A direct, rapid, quantitative colorimetric assay to determine neutrophil primary granule degranulation was adapted for use with fathead minnow kidney neutrophils. The assay measures the exocytosis of myeloperoxidase (MPO) using 3,3',5,5'-tetramethylbenzidine as a substrate. The assay was validated by comparing the total myeloperoxidase content of neutrophil populations obtained from adult cattle, as a known positive, and fish; evaluating the effects of calcium ionophore (CaI), phorbol myristate acetate (PMA), aqueous solution of beta-glucan (MGAQ) and zymosan (Z) with and without cytochalasin B (cyto B) as stimulants of degranulation; determining the kinetics of primary granule exocytosis and detecting changes in degranulation when fish were exposed to stress and anaesthesia with MS-222. The MPO assay detected MPO activity in fathead minnow neutrophils that correlated to neutrophil numbers, confirmed that degranulation was increased when CaI was used compared to other stimulants, determined degranulation peak at 60 min and confirmed decreased degranulation after exposure to handling and crowding stress, with and without MS-222. Therefore, the MPO assay is capable of detecting important differences that may occur in degranulation of fathead minnow kidney neutrophil primary granules and in total neutrophil myeloperoxidase content.

Rhinitis/Bronchopneumonia Syndrome in Irish Wolfhounds

This study describes the clinical, immunologic, genetic, and pathologic features of Irish Wolfhounds with rhinitis/bronchopneumonia syndrome. The dogs examined were from Belgium, The Netherlands, UK, Canada, Germany, and Switzerland. Signs included transient to persistent mucoid or mucopurulent rhinorrhea, cough, and respiratory dyspnea. Radiographic, rhinoscopic, and bronchoscopic findings were variable. Analysis of ciliary ultrastructure was performed in 5 affected dogs, but no characteristic primary ciliary defects (primary ciliary dyskinesia) were detected. Serum and bronchoalveolar lavage fluid (BALF) concentrations of IgA, IgG, and IgM were determined in some affected dogs and clinically normal Irish Wolfhounds. Serum IgA concentration was below the reference range in 5 of 8 affected dogs tested, whereas BALF IgA concentration was above the normal range in 2 affected adult dogs. The CD4 to CD8 lymphocyte subset ratio (CD4:CD8) in peripheral blood was tested in 3 affected dogs and was within the normal range. BALF CD4:CD8 was tested in 1 affected dog and was higher than the normal range. Decreased neutrophil phagocytosis was observed in 1 of the 4 dogs tested. Analysis of pedigrees of the Belgian, Canadian, German, and Swiss dogs revealed common ancestry, suggesting a heritable syndrome.

Evaluation of neutrophilic function (chemotaxis, phagocytosis and microbicidal activity) in healthy dogs and in dogs suffering from recurrent deep pyoderma

The modified Boyden's technique of chemotaxis ('leading front' method) and the bacterial killing test with Staphylococcus sp. stained with acridine orange were performed with suspensions of granulocytes from 50 healthy dogs. Lipopolisacharide of Escherichia coli, in normal dog serum was used as the chemotactic factor. The mean value for the chemotactic differential found was 30.41 +/- 12.14 mu. The optimal concentration of bacteria and opsonins (normal dog serum) was 4 and 15%, respectively, and the ideal incubation period was 30 min. The mean values obtained for phagocytosis percentage, number of bacteria per PMN, phagocytosis index and percentage of dead bacteria, were 97.01 +/- 3.22%, 22.20 +/- 4.6, 21.53 +/- 4.50 and 45.30 +/- 9.18%, respectively. Granulocyte functions in 18 dogs with recurrent, chronic, deep pyoderma were assessed by the same methods. No significant difference between the two groups, for any of the evaluated parameters, was found. For elucidation of the pathogenesis of recurrent pyoderma, further studies involving humoral and cellular immunity and the complement system are required.

Neutrophil phagocyte dysfunction in a weimaraner with recurrent infections

A five-and-a-half-month-old male weimaraner with severe recurrent bacterial infections was assessed for immunocompetence. Results revealed a low serum immunoglobulin G concentration and defective neutrophil phagocytosis.

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.

Immune functions of veal calves fed low amounts of iron

Immune functions were studied in male calves fed milk replacer (MR) containing 10 or 50 mg iron (Fe)/kg. Calves fed 10 mg Fe/kg MR developed marked hypoferremia and anemia, whereas serum-Fe and haemoglobin concentration of calves fed 50 mg Fe/kg MR were normal. Growth performance was reduced, while feed/gain ratio, incidence of infections (especially pneumonias), febrile body temperatures and antibiotic treatments were higher in calves fed 10 than 50 mg Fe/kg MR (p < 0.05). Whereas antibody production (to horse erythrocytes) and lymphocyte stimulation (by mitogens) were not significantly altered, cell-mediated immunity (measured as cutaneous delayed-type hypersensitivity reaction to dinitrofluoro-benzene), number of neutrophils with phagocytic capacity, activity of the Fe-containing enzyme myeloperoxidase, blood serum IgG concentration and the number and diameter of germinal centres as a measure of the number and production of B-cells in cervical superficial lymph nodes in calves fed 10 mg Fe/kg MR were reduced when compared with calves fed 50 mg Fe/kg MR (p < 0.05). In conclusion, severe Fe deficiency caused reduced growth performance, associated with and partly due to higher incidence of infections because of defective immune reactions.

Defective in vitro motility of polymorphonuclear leukocytes of homozygote and heterozygote Chediak-Higashi cats

The in vitro migratory responses of neutrophils of homozygote and heterozygote Chediak-Higashi cats were defective in an under-agarose assay when compared to the behavior of phagocytes of control cats. The linear distances traversed by the leading front of migrating Chediak-Higashi neutrophils toward streptococcal culture supernatant, zymosan-activated serum or buffer were reduced and smaller numbers of Chediak-Higashi phagocytes populated the resulting migration areas than did cells of control animals. The relative migration parameters of the Chediak-Higashi phagocytes, however, did not differ from the corresponding parameters of control neutrophils in the presence of streptococcal culture supernatant. Therefore, phagocytes of homozygote and heterozygote Chediak-Higashi cats recognized and responded equally well to the bacterial stimuli as did cells of control animals but traveled shorter distances primarily because of a reduced inherent motility. Similar results were also obtained when the feline phagocytes were attracted by zymosan-activated serum. In addition the relative migration parameters of the neutrophils of homozygote Chediak-Higashi cats were reduced and the normalized spatial distributions of their migrating cells were significantly different in the presence of 100% and 20% zymosan-activated serum when compared to the corresponding migration parameters of carrier and control animals. Defective recognition or responses to the higher concentrations of these host-derived attractants complicated, therefore, the already reduced inherent motility of the phagocytes of homozygote Chediak-Higashi cats.

Heterophil function in healthy chickens and in chickens with experimentally induced staphylococcal tenosynovitis

Heterophil function was evaluated in 16 healthy chickens and in 46 chickens with experimentally induced staphylococcal tenosynovitis. In paired blood samples, heterophils from chickens with tenosynovitis had a significant increase in adherence, chemotaxis, phagocytosis, and bacterial killing of Staphylococcus aureus compared to heterophils from healthy chickens. The percent adherence of heterophils to nylon fiber columns increased significantly from a 78.4% mean +/- 6.6% standard deviation to 87.6% +/- 3.2% after induction of staphylococcal tenosynovitis. Heterophil movement following in vitro exposure to saline or endotoxin was increased in chickens with tenosynovitis; 3 +/- 1 heterophils/0.25 mm2 to 10 +/- 6 heterophils/0.25 mm2 and 136 +/- 29 heterophils/0.25 mm2 to 340 +/- 74 heterophils/0.25 mm2, respectively. Endotoxin-activated serum was chemoattractive for heterophils from all chickens. Flow cytometry was used to define the heterophil population on light scatter histograms, evaluate individual cell phagocytosis of latex beads, and quantitate the number of beads phagocytosed per heterophil. When incubated with increased numbers of beads, only heterophils from chickens with tenosynovitis phagocytosed higher numbers of beads. At heterophil to bead ratios of 1:10, the percentage of heterophils that phagocytosed beads increased from baseline values of 37.8% +/- 9.0% to post-infection values of 67.3% +/- 7.5%. Using 1:20 heterophil to bead ratios, heterophil phagocytosis increased from 38.7% +/- 9.9% to post-infection values of 79.8% +/- 7.3%. Heterophils from all chickens were able to phagocytose and kill log phase staphylococcal bacteria. After phagocytosis, the heterophils from chickens with staphylococcal tenosynovitis rapidly decreased the number of viable bacterial colony forming-units per milliliter by approximately one log.(ABSTRACT TRUNCATED AT 250 WORDS)

Porcine granulocyte functions: evaluation and modulation

Functions of porcine polymorphonuclear neutrophils are evaluated with in vitro test systems. Results are compared with those from human PMN and the relevance for in vivo conditions is discussed. Ethanol was inhibitory to all porcine PMN functions investigated here. Influex, a combination product, containing extracts of Echinacea, Aconitum, Apis and Lachesis stimulated adherence, chemotaxis, and phagocytosis, but inhibited chemiluminescence. These results suggest an effect of the product in the generation of reactive oxygen species.

Chemiluminescence and chemotaxis assay of porcine polymorphonuclear cells. A methodological study

A Boyden-Chamber technique for leukocyte migration was adapted to a polymorphonuclear (PMN) cell concentration of 5 x 10(6) cells/ml an optimal amount of cells for the leading front technique. Casein (0.1%) is so far the most effective chemotactic substance for porcine granulocytes. A formylpeptide++, FMLP (in concentrations of 10(-2) to 10(-10) mmol/l), does not stimulate migration in porcine granulocytes when compared to random migration. For the chemiluminescence assay a concentration of 5 x 10(6) PMN cells/ml buffer is needed to obtain optimal conditions in pig granulocytes. Moreover the chemiluminescence should be performed within a standardized interval after the isolation of leukocytes since the cell activity declines rapidly after the isolation. The chemiluminescence and migration assays were standardized at 37 degrees C; the activity of the granulocytes did not show any significant variation within a temperature interval of 37-39 degrees C, whereas temperatures below 37 degrees C significantly reduce the granulocytic activity.

Clinical interpretation of leukocyte responses

Basic information has been presented concerning leukocyte (neutrophil, monocyte, lymphocyte, eosinophil, and basophil) function, production, kinetics, and response to various physiological and disease states. Using this information, veterinary practitioners should be able to interpret leukogram data from sick and healthy dogs and cats. Specifically, characteristic leukogram patterns such as physiological leukocytosis, corticosteroid-associated changes, and the presence of infection or severe inflammation should be recognized. In addition, interpretation of individual leukocyte responses should be possible. Several tables have been provided to assist in constructing a differential diagnosis to explain increases or decreases in absolute leukocyte numbers that lie outside of expected reference intervals.

Granulocyte isolation from whole blood of goat, sheep, cattle, horse, dog, pig, and man

A simple two step procedure for the isolation of caprine, ovine, bovine, equine, canine, porcine and human peripheral blood granulocytes is described. After enrichment of granulocytes by centrifugation, contaminating erythrocytes are lysed hypotonically. Recovery, purity, and viability of the granulocyte suspensions are determined. FACScan analysis of the cell suspensions measuring cellular size by forward and sideward light scatter is compared with the corresponding analysis of whole blood leukocytes. Constituencies of the isolated cell suspensions and loss of granulocyte subpopulations through isolation procedure is discussed with regard to granulocyte function assays.

Comparative studies on the adhesiveness of granulocytes of guinea pig and man

The high affinity of granulocytes of guinea pig and man to glass surfaces is modified by serum. Native serum contains both an adherence-promoting activity, which is related to complement, and components which reduce the adhesiveness of granulocytes. These components are stable at 56 degrees C for 30 min and are tightly bound to the glass surface. beta-Lipoproteins are candidates for this adherence reducing ability of serum. Adherence promotion by native serum is mediated by coating the glass surface with C3b/C3bi. Human granulocytes from the peripheral blood adhered pig serum with C3b/C3bi to almost the same extent as in the presence of native serum, but on guinea pig granulocytes elicited in the peritoneal cavity, a cell surface metalloproteinase degraded the C3b/C3bi, thus reducing the adhesiveness of these cells. This proteinase was inhibited by MgEDTA, DTT, and 1,10-phenanthroline, whereby the high adhesiveness of granulocytes was restored to C3b/C3bi-coated glass.

Effect of ovarian steroids on migration of uterine lumenal neutrophils and on chemokinetic factors in uterine secretions from mares

Incubation of blood neutrophils with uterine flushings collected from ovariectomised mares treated with oestradiol, stimulated migration under agarose, whereas flushings from mares treated with progesterone or oily vehicle, inhibited migration. After intra-uterine infusion of bacteria, however, flushings from oestradiol-treated and vehicle-treated mares inhibited migration, whereas progesterone treatment stimulated migration. Migration of uterine-derived neutrophils under agarose was less than that of blood neutrophils and was not influenced by treatment with ovarian steroids. Uterine susceptibility to infection in progesterone-treated mares was not, therefore, correlated with the migratory activities of uterine neutrophils or the chemokinetic properties of uterine secretions in vitro.

Bovine leukocyte phagocytosis and bacteria killing monitored by intracellular acridine orange fluorescence and extracellular fluorescence quenching

The time course of phagocytosis and intracellular killing of serum-opsonized Escherichia coli K12 and Staphylococcus aureus SG511 by glass-adherent bovine peripheral blood polymorphonuclear leukocytes (PMNLs) and cultured monocytes (macrophages) was monitored by fluorescence microscopy of single cells using the acridine orange (AO)/crystal violet (CV) technique. After interaction of glass-adherent leukocytes (20, 40, 60 min, 37 degrees C) with opsonized bacteria, cells were stained with the fluorescent dye AO. Living bacteria stained green, dead bacteria stained orange. The addition of CV to AO-stained bacteria quenched the fluorescence of extracellular bacteria only. CV does not penetrate living bovine PMNLs which allows the discrimination of ingested (fluorescent) and extracellular (nonfluorescent) bacteria during attachment and phagocytosis of bacteria by adherent PMNLs. We investigated quantitatively phagocytosis and intracellular killing of serum-opsonized bacteria by bovine PMNLs from 22 bulls of 4 different Swiss dairy breeds. Within 60 min maximum uptake (approximately 12 bacteria/PMNL) and killing (approximately 80%) of serum-opsonized Escherichia coli K12 and Staphylococcus aureus SG511 were achieved. The AO/CV technique was also used to quantify the uptake and intracellular killing of serum-opsonized Escherichia coli K12 by cultured monocytes (macrophages). Within 60 min maximum uptake of bacteria (approximately 16/MO) was achieved; approximately 83% of bacteria were killed.

Amoeboid movement: a review and proposal of a 'membrane ratchet' model

Diverse cell types, including Amoebae, leukocytes, embryonic cells and tumour cells move about on solid surfaces to accomplish such activities as feeding, bacterial destruction, embryological development and metastasis. Theories of the mechanism of this movement are reviewed and a model is proposed which invokes the existence of specific, laterally mobile, transmembranous structures in the cell membrane, which are reversibly adhesive for both the contractile apparatus of the cell internally, and the substratum externally. By this model, the movement of all these cell types can be explained.

Entamoeba histolytica: chemoattractant activity for gerbil neutrophils in vivo and in vitro

The kinetics of the host's cellular response in the peritoneal cavity of gerbils toward axenic pathogenic and nonpathogenic Entamoeba histolytica strains were examined. Amebae contained in diffusion chambers or free in the peritoneum elicited a neutrophilic response accompanied by decreased levels of macrophages and lymphocytes. Pathogenic amebae (IP:0682:1 strain) elicited a neutrophilic response greater than the nonpathogenic DKB and "entamoeba-like" Laredo amebae. The neutrophil eliciting factor was found in high levels in disrupted freeze-thawed amebae (53% elicited neutrophils vs 8% for control), glutaraldehyde fixed amebae (45%) and amebic membranes (65%), and low levels in conditioned amebic medium (15%) and the supernatant fraction of amebae (16%). The factor was heat stable to high temperature (100 C for 30 min) and at various pH (6 to 9). The neutrophil eliciting factor in amebic membranes was lowered following pretreatment for 30 min with 1% immune and nonimmune gerbil or human sera (34-48% lowered neutrophil response vs control), acidic pH (less than 3, 69%), proteolytic digestion [trypsin (68%) and alpha-chymotrypsin (72%), 100 micrograms/ml], and 2% Triton X-100 (75%). Peritoneal neutrophils isolated following stimulation with amebic membranes or thioglycollate medium demonstrated higher chemotaxis in vitro toward live pathogenic amebae and amebic membranes (IP:0682:1 strain) compared to either the supernatant fraction or the nonpathogenic DKB or Laredo amebae. The results of this study indicate that membrane bound proteins of pathogenic amebae are chemotactic for gerbil neutrophils which may be important in the pathogenesis and pathology of amebiasis.

Effects of stallion seminal plasma on hydrogen peroxide release by leukocytes exposed to spermatozoa and bacteria

The ability of stallion seminal plasma to modify phagocytosis of spermatozoa and Streptococcus zooepidemicus was examined. Phagocytosis was monitored indirectly as the H2O2 produced by peripheral blood leukocytes after addition of spermatozoa or bacteria. Hydrogen peroxide production after addition of ejaculated spermatozoa was greater (P less than 0.01) than after addition of epididymal sperm. Furthermore, pre-incubation of epididymal sperm with 6.25-50% seminal plasma caused a dose-dependent increase in subsequent H2O2 production by leukocytes (P less than 0.05). In addition, equine serum was capable of opsonizing epididymal and ejaculated sperm. Seminal plasma also directly stimulated phagocyte function because leukocytes preincubated with 12.5% or 25% seminal plasma released more H2O2 after addition of S. zooepidemicus than control leukocytes (P less than 0.05). It is suggested that the opsonization of spermatozoa and the direct stimulation of phagocytes by seminal plasma may represent mechanisms for clearing spermatozoa and bacteria from the reproduction tract.

Phagocytic function of polymorphonuclear leukocytes and the RES in endotoxemia

The reticuloendothelial system (RES) and the polymorphonuclear leukocytes (PMNs) are thought to play a major role in defense against sepsis. Disturbances in the function of these two phagocytic systems during a septic event is associated with the development of lung capillary injury. Endotoxemia is said to lead to similar changes. Our study examined the function of the RES and PMNs after bolus injection of endotoxin (2 micrograms/kg BW) in a standardized sheep model. For up to 24 hr after endotoxin, blood samples were drawn and PMN function was followed by chemiluminescence, chemotaxis, and adherence as well as the phagocytosis and killing of bacteria. RES function was determined by the blood clearance of a labeled Tc99 colloid. We found an increase of RES clearance directly after endotoxin. Chemotaxis, phagocytosis, and killing were reduced. Adherence was increased. Chemiluminescence peak maximum (CLPM), representing the metabolic activity of the PMNs, was initially increased but shortly thereafter showed a significant decline (at 1 hr: 0.52 +/- 0.13 X 10(6) cpm with P less than 0.05 compared to baseline). The chemiluminescence peak time (CLPT), a measure of membrane receptor function, was significantly reduced (10.0 +/- 2.2 min with P less than 0.001 compared to baseline). Endotoxin led to a reduction of intracellular PMN functions (phagocytosis, killing, CLPM) within 1 hr. Membrane localized functions (adherence, CLPT) were increased. The changes in PMN function might be the reason for the development of lung capillary injury, in spite of undisturbed RES clearance.

Opsonization of bacteria by uterine secretions of cyclic mares

Uterine flushings collected from mares before and after bacterial-induced inflammation were assayed for ability to opsonize Streptococcus zooepidemicus for phagocytosis by polymorphonuclear leukocytes. Opsonization was measured as the peak phagocytic rate of bacteria preincubated with uterine flushings relative to the peak phagocytic rate of unopsonized bacteria. Flushings from four mares with noninfected uteri were unable to opsonize bacteria regardless of whether uteri were flushed at estrus or on day 10 postovulation. In a second experiment, 7 X 10(9) live S. zooepidemicus were inoculated into the uterus of five mares during estrus. Uterine flushings collected at the estrus before inoculation or at the estrus after inoculation did not opsonize bacteria. Four of five flushings collected 6 hr post inoculation, however, were capable of opsonization. Based on heat inactivation at 56 degrees C, the opsonizing activity of one of four flushes was due to a complement protein. It was concluded that one aspect of the acute inflammatory response of the mare's uterus is accumulation of opsonins in the uterine lumen.