Monoclonal antibodies raised to human cells--specificity for pig leukocytes

Splenic Nerve Neuromodulation Reduces Inflammation and Promotes Resolution in Chronically Implanted Pigs

Neuromodulation of the immune system has been proposed as a novel therapeutic strategy for the treatment of inflammatory conditions. We recently demonstrated that stimulation of near-organ autonomic nerves to the spleen can be harnessed to modulate the inflammatory response in an anesthetized pig model. The development of neuromodulation therapy for the clinic requires chronic efficacy and safety testing in a large animal model. This manuscript describes the effects of longitudinal conscious splenic nerve neuromodulation in chronically-implanted pigs. Firstly, clinically-relevant stimulation parameters were refined to efficiently activate the splenic nerve while reducing changes in cardiovascular parameters. Subsequently, pigs were implanted with a circumferential cuff electrode around the splenic neurovascular bundle connected to an implantable pulse generator, using a minimally-invasive laparoscopic procedure. Tolerability of stimulation was demonstrated in freely-behaving pigs using the refined stimulation parameters. Longitudinal stimulation significantly reduced circulating tumor necrosis factor alpha levels induced by systemic endotoxemia. This effect was accompanied by reduced peripheral monocytopenia as well as a lower systemic accumulation of CD16+CD14high pro-inflammatory monocytes. Further, lipid mediator profiling analysis demonstrated an increased concentration of specialized pro-resolving mediators in peripheral plasma of stimulated animals, with a concomitant reduction of pro-inflammatory eicosanoids including prostaglandins. Terminal electrophysiological and physiological measurements and histopathological assessment demonstrated integrity of the splenic nerves up to 70 days post implantation. These chronic translational experiments demonstrate that daily splenic nerve neuromodulation, via implanted electronics and clinically-relevant stimulation parameters, is well tolerated and is able to prime the immune system toward a less inflammatory, pro-resolving phenotype.

The UK Veterinary Immunological Toolbox Website: promoting vaccine research by facilitating communication and removing reagent barriers

Using the best animal models to study immune responses against specific pathogens or vaccines can dramatically accelerate our understanding. Veterinary species are well studied, particularly livestock, to reduce their disease burden. They have also proven to be powerful models, especially for zoonotic pathogens and novel vaccination strategies. A prerequisite for any model selection is having the right quality and range of species‐specific immunological reagents. To help promote the widest possible use of veterinary species, an open access website (https://www.immunologicaltoolbox.co.uk) has been created as a central community annotated hub for veterinary immunological reagents. The website is also the portal into services offered by the UK Immunological Toolbox project that includes antibody generation, sequencing and recombinant expression. The funding for this effort is linked into sustainable sources, but ultimate success relies on community engagement to continually increase the quality and quantity of information. It is hoped that as more users and reagent owners engage, it will become an essential resource for researchers, veterinarians and clinicians alike by removing barriers that prevent the use of the most informative animal models.

Immunophenotyping: Application to Safety Assessment

A continuing education course entitled “What You Always Wanted to Know About Immunotoxicology in Pharmaceutical Development…But Were Afraid to Ask” was offered at the Society of Toxicologic Pathology (STP) 36th annual symposium in Montreal. This article summarizes some key points made during the presentation dedicated to immunophenotyping. It describes how clusters of differentiation (CDs) are well-defined antigens used to characterize cell subsets, and how lymphocyte subsets in humans and different rodent and nonrodent species can be defined by detection of various combinations of CDs. It provides an overview of immunophenotyping study design considerations and applications to safety assessment.

Expanding the tools for identifying mononuclear phagocyte subsets in swine: Reagents to porcine CD11c and XCR1

Pig is a domestic species of major importance in the agro-economy and in biomedical research. Mononuclear phagocytes (MNP) are organized in subsets with specialized roles in the orchestration of the immune response and new tools are awaited to improve MNP subset identification in the pig. We cloned pig CD11c cDNA and generated a monoclonal antibody to pig CD11c which showed a pattern of expression by blood and skin MNP subsets similar to humans. We also developed a porcine XCL1-mCherry dimer which specifically reacted with the XCR1-expressing dendritic cell subset of the type 1 lineage in blood and skin. These original reagents will allow the efficient identification of pig MNP subsets to study their role in physiological and pathological processes and also to target these cells in novel intervention and vaccine strategies for veterinary applications and preclinical evaluations.

Characterization of the atypical lymphocytes in African swine fever

Aim:

Atypical lymphocytes usually described as lymphocytes with altered shape, increased DNA amount, and larger size. For analysis of cause of genesis and source of atypical lymphocytes during African swine fever virus (ASFV) infection, bone marrow, peripheral blood, and in vitro model were investigated.

Materials and Methods:

Atypical lymphocytes under the influence of ASFV were studied for morphologic, cytophotometric, and membrane surface marker characteristics and were used in vivo and in vitro models.

Results:

This study indicated the increased size, high metabolic activity, and the presence of additional DNA amount in atypical lymphocytes caused by ASFV infection. Furthermore, in atypical lymphocytes, nuclear-cytoplasmic ratio usually decreased, compared to normal lymphocytes. In morphology, they looking like lymphocytes transformed into blasts by exposure to mitogens or antigens in vitro. They vary in morphologic detail, but most of them are CD2 positive.

Conclusions:

Our data suggest that atypical lymphocytes may represent an unusual and specific cellular response to ASFV infection.

The development and validation of methods for evaluating the immune system in preweaning piglets

The preweaning piglet has been found to be a valuable research model for testing ingredients used in infant formula. As part of the safety assessment, the neonates' immune system is an important component that has to be evaluated. In this study three concurrent strategies were developed to assess immune system status. The methods included (1) immunophenotying to assess circulating innate immune cell populations, (2) monitoring of circulating cytokines, particularly in response to a positive control agent, and (3) monitoring of localized gastrointestinal tissue cytokines using immunohistochemistry (IHC), particularly in response to a positive control agent. All assays were validated using white papers and regulatory guidance within a GLP environment. To validate the assays precision, accuracy and sample stability were evaluated as needed using a fit for purpose approach. In addition animals were treated with proinflammtory substances to detect a positive versus negative signal. In conclusion, these three methods were confirmed to be robust assays to evaluate the immune system and GIT-specific immune responses of preweaning piglets.

Pig peripheral blood mononuclear leucocyte subsets are heritable and genetically correlated with performance

Indicator traits used to select pigs for increased resistance to infection or improved health must be heritable and, preferably, be associated with improved performance. We estimated the heritability of a range of immune traits and their genetic and phenotypic correlations with growth performance. We measured immune traits on 589 pigs and performance on 1941 pigs from six farms, three of which were classified as 'high health status' (i.e. specific pathogen-free) and three were of lower health status. All pigs were apparently healthy. Immune traits were total white blood cells (WBC), and peripheral blood mononuclear leucocyte (PBML) subsets positive for CD4, CD8α, gamma delta (γδ) T cell receptor, CD11R1 (natural killer cell marker), B cell and monocyte markers at the start and the end of standard growth performance tests. At both time points, all immune traits were moderately to highly heritable except for CD8α+ cells. At end of test, heritability estimates (h2) (±s.e.) were 0.18 (±0.11) for total WBC count. For PBML subset proportions, the heritabilities were 0.52 (±0.14) for γδ TCR+ cells, 0.62 (±0.14) for CD4+ cells, 0.44 (±0.14) for CD11R1+ cells, 0.58 (±0.14) for B cells and 0.59 (±0.14) for monocytes. Farm health status affected the heritabilities for WBC, being substantially higher on lower health status farms, but did not have consistent effects on heritabilities for the PBML subsets. There were significant negative genetic correlations between numbers and proportions of various PBML subsets and performance, at both start and end of test. In particular, the proportion of PBML cells that were CD11R1+ cells, at end of test, was strongly correlated with daily gain (rg = -0.72; P < 0.01). There were also weaker but significant negative phenotypic correlations between PBML subsets measured at end of test and performance, for γδ+ T cells, CD8α+, CD11R1+ cells, B cells or monocytes. Phenotypic correlations with daily gain were generally lower at the start of test than at the end of test. These results show that most of the major pig PBML subsets are heritable, and that systemic levels of several of these PBML subsets are genetically negatively correlated with performance. This approach provides a basis for using immune trait markers when selecting boars that can produce higher-performing progeny.

Neonatal colonisation expands a specific intestinal antigen-presenting cell subset prior to CD4 T-cell expansion, without altering T-cell repertoire

Interactions between the early-life colonising intestinal microbiota and the developing immune system are critical in determining the nature of immune responses in later life. Studies in neonatal animals in which this interaction can be examined are central to understanding the mechanisms by which the microbiota impacts on immune development and to developing therapies based on manipulation of the microbiome. The inbred piglet model represents a system that is comparable to human neonates and allows for control of the impact of maternal factors. Here we show that colonisation with a defined microbiota produces expansion of mucosal plasma cells and of T-lymphocytes without altering the repertoire of alpha beta T-cells in the intestine. Importantly, this is preceded by microbially-induced expansion of a signal regulatory protein α-positive (SIRPα⁺) antigen-presenting cell subset, whilst SIRPα⁻CD11R1⁺ antigen-presenting cells (APCs) are unaffected by colonisation. The central role of intestinal APCs in the induction and maintenance of mucosal immunity implicates SIRPα⁺ antigen-presenting cells as orchestrators of early-life mucosal immune development.

Dendritic cells interact with CD4 T cells in intestinal mucosa

Absence of lymph nodes in nonmammalian species, expression of MHCII by APCs in the periphery, and the recent findings that T cells can change their polarization status after presentation in the lymph nodes imply a role for MHCII-mediated presentation outside the organized lymphoid tissue. This study shows that MHCII(+) ECs and DCs from the intestinal mucosa of the pig can present antigen to T cells in vitro. In vivo, APCs colocalize with T cells in pig and mouse intestinal mucosa. In the pig, endothelium is involved in these interactions in neonates but not in adults, indicating different roles for stromal and professional APCs in the neonate compared with the adult. The ratio of expression of DQ and DR MHCII locus products was lower on ECs than on other mucosal APCs, indicating that the two types of cells present different peptide sets. Adult nonendothelial APCs expressed a higher ratio of DQ/DR than in neonates. These results suggest that mucosal DCs can present antigen locally to primed T cells and that stromal APCs are recruited to these interactions in some cases. This raises the possibility that local presentation may influence T cell responses at the effector stage after initial presentation in the lymph node.

Traits associated with innate and adaptive immunity in pigs: heritability and associations with performance under different health status conditions

There is a need for genetic markers or biomarkers that can predict resistance towards a wide range of infectious diseases, especially within a health environment typical of commercial farms. Such markers also need to be heritable under these conditions and ideally correlate with commercial performance traits. In this study, we estimated the heritabilities of a wide range of immune traits, as potential biomarkers, and measured their relationship with performance within both specific pathogen-free (SPF) and non-SPF environments. Immune traits were measured in 674 SPF pigs and 606 non-SPF pigs, which were subsets of the populations for which we had performance measurements (average daily gain), viz. 1549 SPF pigs and 1093 non-SPF pigs. Immune traits measured included total and differential white blood cell counts, peripheral blood mononuclear leucocyte (PBML) subsets (CD4⁺ cells, total CD8α⁺ cells, classical CD8αβ⁺ cells, CD11R1⁺ cells (CD8α⁺ and CD8α^-), B cells, monocytes and CD16⁺ cells) and acute phase proteins (alpha-₁ acid glycoprotein (AGP), haptoglobin, C-reactive protein (CRP) and transthyretin). Nearly all traits tested were heritable regardless of health status, although the heritability estimate for average daily gain was lower under non-SPF conditions. There were also negative genetic correlations between performance and the following immune traits: CD11R1⁺ cells, monocytes and the acute phase protein AGP. The strength of the association between performance and AGP was not affected by health status. However, negative genetic correlations were only apparent between performance and monocytes under SPF conditions and between performance and CD11R1⁺ cells under non-SPF conditions. Although we cannot infer causality in these relationships, these results suggest a role for using some immune traits, particularly CD11R1⁺ cells or AGP concentrations, as predictors of pig performance under the lower health status conditions associated with commercial farms.

Development of perioperative care for pigs undergoing laryngeal transplantation: a case series

Pigs are ideal animal models for airway surgical research, facilitating the successful translation of science into clinical practice. Despite their ubiquitous use, there is a paucity of information on the perioperative care of pigs, especially for major procedures. In a series of experiments to investigate laryngeal transplantation, we combined veterinary and medical experience to develop protocols for perioperative management of pigs, including high dependency care. Novel airway management methods were developed. A pain scoring system was used to direct analgesia use. Fluid balance and electrolytes were monitored closely. Recent animals received a central venous line via the femoral vein two days prior to transplantation to facilitate blood sampling and drug delivery. Intensive monitoring and airway management were required to ensure a successful outcome. Methods for optimal perioperative care are proposed. These results will help future groups wishing to use pigs in airway research, will reduce numbers of animals used and improve animal welfare.

Porcine myelomonocytic markers and cell populations

This review focuses in what is currently known about swine myeloid markers, the expression and function of these receptors in the biology of porcine myelomonocytic cells, the regulation of their expression along the different developmental stages of these cells and their utility to investigate the heterogeneity of monocyte and macrophage populations. Although the number of monoclonal antibodies recognizing surface antigens expressed on either swine granulocytes or monocytes is low compared with those available for human or mouse, they have contributed significantly to study the members of myeloid lineages in this species, allowing to discriminate different maturation stages of these cells in bone marrow and to reveal the heterogeneity of blood monocytes and tissue macrophages. Porcine myeloid cells share many similarities with humans, highlighting the relevance of the pig as a biomedical model.

The mucosal immune system: recent developments and future directions in the pig

In most animals, the mucosal immune system effectively controls expression of active immune responses to pathogen and tolerance to harmless antigens. Our understanding of the function and control of the mucosal immune system has advanced as a result of studies in rodents and humans. The discoveries of regulatory T-cells and T-helper-17 cells, and studies on the interactions between epithelial and dendritic cells, demonstrate its complexity. In pigs, some of the systems and reagents for determining the relevance of these mechanisms are present, and indicate lines for future work. However, many empirical studies of the effect of manipulation of the mucosal immune system in the pig by prebiotics, probiotics and feed additives have been carried out. Interpretation of these results needs to be made with care, since manipulation of the mucosal immune system may improve its efficiency under a specific set of environmental and husbandry conditions, but impair it under others.

Membrane markers of the immune cells in swine: an update

Besides their breeding value, swine are increasingly used as biomedical models. As reported in three international swine clusters of differentiation (CD) workshops and in the animal homologue section of the last workshop for the determination of human leukocyte differentiation antigens (HLDA 8), characterisation of leukocyte surface antigens by monoclonal antibodies and other molecular studies have determined the cell lineages and blood leukocyte subsets implicated in the immune response, including cell adhesion molecules involved in cell trafficking. This review focusses on the current state of knowledge of porcine leukocyte differentiation and major histocompatibility complex (SLA) molecules. Examples of porcine particularities such as the double-positive T lymphocytes with the phenotype CD(4+)CD8(low) and CD(4-)CD8(low) alphabeta T cell subsets and the persistence of SLA class II after T-lymphocyte activation are illustrated, as well as the shared characteristics of the Artiodactyla group, such as the high proportion of gammadelta TcR (T cell receptor) T cells in blood and other lymphoid tissues. Furthermore, discrepancies between swine and humans, such as CD16 expression on dendritic cells and CD11b (wCD11R1) tissue distribution are outlined. The rapidly growing information should facilitate manipulation of the swine immune system towards improving disease control, and open new avenues for biomedical research using the pig as a model.

Primitive hematopoietic cell populations reside in the spleen: Studies in the pig, baboon, and human

OBJECTIVE

We previously observed high levels (>40%) of multilineage hematopoietic cell chimerism following spleen transplantation across full MHC barriers in immunosuppressed miniature swine. We therefore investigated the spleen as a source of hematopoietic progenitor cells (HPCs).

MATERIALS AND METHODS

Specific cell-surface markers were used to identify HPCs in the spleen and bone marrow (BM) of young adult (n = 15) and fetal (n = 9) miniature swine by flow cytometry. Hoechst dye-effluxing side population (SP) cells were analyzed in adult spleen, BM, and blood for their expression of c-kit. Functional HPC activity of varying repopulation potential in vitro was investigated by the ability of spleens and BM to give rise to colony-forming units (CFUs) and cobblestone area-forming cells (CAFCs) in long-term stromal cultures. Studies were also carried out on baboon and human spleens and BM.

RESULTS

Spleen c-kit+ cells co-expressed more lymphoid markers, but equal myeloid markers, when compared with BM c-kit+ cells. BM and spleen both contained significant percentages of c-kit+ SP cells. Although the frequency of early-forming CFUs in the spleen was only 0.1 to 1.3% of that in the BM, the frequency of CAFCs developing after 8 weeks in culture was comparable to that of BM. Secondary CFUs in long-term culture-initiating cell assays confirmed the presence of long-term repopulating cells at comparable frequencies in spleen and BM. Similar findings were found with regard to baboon and human spleen cells.

CONCLUSION

The adult spleen is a relatively rich source of very primitive HPCs, possibly hematopoietic stem cells (HSCs), and may be of therapeutic value.

Classical swine fever virus induces activation of plasmacytoid and conventional dendritic cells in tonsil, blood, and spleen of infected pigs

Classical swine fever virus (CSFV) compromises the host immune system, causing indirect leucopoenia and disruption of in vitro T cell stimulation capacity. In order to explore the potential role of dendritic cells (DC) in such phenomena, the activation of conventional DC (cDC) and plasmacytoid DC (pDC) in blood and secondary lymphoid organs of infected pigs was investigated in the early time course post-inoculation (pi), together with viral components dissemination and cytokine production in serum. Whereas CD11R1+CD172a+ cDC frequencies were markedly reduced in blood and spleen, analysis of CD4+CD172a+ pDC numbers revealed a rapid turn-over of this DC subset in tissues pi. Both subsets matured and were activated after infection, as demonstrated by down-regulation of CD1a, up-regulation of the co-stimulation molecule CD80/86 and expression of cytokines. cDC essentially expressed tumor necrosis factor alpha (TNF-alpha) and interleukin (IL)-10, whereas pDC produced alpha interferon (IFN-alpha) and IL-12. IFN-alpha and TNF-alpha productions revealed an enhancement of innate anti-viral immune responses. Detection of antigen activated B lymphocytes in tonsil T-cell areas at 72 h pi, subsequently to the transient translocation of the viral E2 protein within germinal centres at 48 h pi, indicates the initiation of humoral response. This response was also evidenced by an important IL-10 production in serum one week pi. IL-12 expression in organs, as well as transient detection of IL-18 and IFN-gamma in serum, reflected the initiation of cellular immune responses. However, the uncommonly high levels of TNF-alpha and IFN-alpha produced by DC and measured in serum early post-infection, together with IL-10 expression in spleen, could play a role in the disruption of immune system cells, either inducing apoptosis or impairing DC functionalities themselves.

The association between plasma levels of acute phase proteins, haptoglobin, alpha-1 acid glycoprotein (AGP), Pig-MAP, transthyretin and serum amyloid A (SAA) in Large White and Meishan pigs

During infection, the acute phase response triggers the release of acute phase proteins (APP), alpha-(1) acid glycoprotein (AGP), serum amyloid A (SAA) and Pig-MAP into the circulation, accompanied by a decrease in plasma levels of transthyretin. We quantified the association between these APP in 26 apparently healthy pigs from two breeds, 13 Large White and 13 Meishan (16 male; 10 female). There was a significant correlation between plasma levels of haptoglobin and Pig-MAP (r=0.57; p<0.05), but no significant associations between any of the other APP tested. We also measured the relationship between PigMAP, transthyretin and SAA, and the proportions of peripheral blood mononuclear sub-sets, CD8(+) cells, CD4(+) cells, CD11R1(+) cells, MHC DQ(+) cells, and monocytes. There were correlations between both plasma levels of Pig-MAP and the proportion of monocytes (r=0.55; p<0.05) and plasma levels of transthyretin and the proportion of MHC DQ(+) cells (r=0.40; p<0.01). Breed and sex influenced plasma levels of Pig-MAP but not plasma levels of transthyretin. Overall, these results suggest closer links between the mechanisms that regulate the release haptoglobin, Pig-MAP and monocytes compared to those that regulate the release of AGP, SAA and transthyretin.

Summary of the animal homologue section of HLDA8

The development of reagents against leukocyte differentiation antigens in veterinary species is delayed compared to mouse and men and therefore also the number of existing reagents for the characterisation of leukocytes derived from species with importance in veterinary medicine is restricted. Cross-reactive studies with existing well defined monoclonal antibodies directed against leukocyte differentiation antigens derived from other species are an alternative approach to enhance the panel of reagents in veterinary immunology. This study describes the activities of the animal homologue section in frame of human leukocyte differentiation antigen 8-workshop (HLDA8) were 376 monoclonal antibodies, mainly directed against human leukocytes had been tested for their reactivity with 17 different animal species including non-human primates, ruminants, swine, horse, carnivores, rabbit, guinea pig, chicken and fish. In a first round 182 mAb were selected based on there reactivity in FCM analyses with at least one species for further studies, including multi-colour FCM, and molecular analyses of the antigens. Interesting was the species-overlapping reactivity of mAb directed against distinct clusters: 11 out of 17 species reacted with CD9, 11 of 17 with CD11a, CD14 (11/17), CD18 (13/17), CD21 (7/17), CD29 (10/17), CD44 (13/17), CD45 (9/17), CD47 (10/17), CD49d (13/17), CD61 (6/17), CD86 (7/17), CD91 (5/17), and CD172a (10/17), indicating evolutionary highly conserved epitopes on these surface molecules. Our results suggest the suitability of cross-reactive mAb for the animal model studies. Moreover, these findings contribute to our understanding of the evolution of the immune system.

Innate immune responses to replication of porcine reproductive and respiratory syndrome virus in isolated Swine alveolar macrophages

Porcine reproductive and respiratory syndrome (PRRS) is an infectious disease caused by a positive RNA strand arterivirus. PRRS virus (PRRSV) interacts primarily with lung macrophages. Identifying the genetic components involved in host resistance/susceptibility would represent an important step forward in the design of disease control programs. In this study, alveolar macrophages derived from five commercial pig lines were used to study the innate immune response to PRRSV infection in vitro. Analysis by flow cytometry has demonstrated that bronchial alveolar lavage fluid (BALF) preparations were almost exclusively composed of alveolar macrophages and that the pigs tested were free from infection. Macrophages from the Landrace line showed significantly reduced virus replication and poor growth of PRRSV during 30 h of infection. By 72 h, PRRSV viral load was down to 2.5 log(10) TCID(50) compared with an average of 5 log(10) TCID(50) for the other breeds tested. These observations suggest that factors intrinsic to the Landrace breed may be responsible for this reduced or delayed response to PRRSV. Preliminary investigation suggests that the PRRSV coreceptor, sialoadhesin, may not be responsible for the Landrace macrophage phenotype as its abundance and localisation were comparable in all the breeds. Strikingly, we found that the reduced or delayed growth of PRRSV was temporally associated with high levels of tumor necrosis factor-alpha (TNF-alpha) and interleukin (IL)-8 mRNA accumulation and substantial reduction of secretion of IL-8, suggesting a key contributory role for cytokine synthesis and secretion during the innate immune response to PRRSV infection.

Selection for lean growth and food intake leads to correlated changes in innate immune traits in Large White pigs

Genetic selection is well established as a means of improving productivity in pigs, but the effects of continued selection for increased performance on immunity are not well understood, nor are genetic relationships between performance and immunity. This study compared differences in the levels of a range of immune traits between lines of Large White pigs divergently selected for a number of productivity traits. Selection lines compared were highv. low lean growth under restricted feeding (31 high linev. 10 controlv. 38 low line pigs), high v. low lean growth underad libitumfeeding (18 high line v. 10 controlv. 19 low line pigs), and highv. low food intake (24 high linev. 26 low line pigs). Immune traits measured were total white blood cell numbers (WBC), and the numbers of leukocyte subsets: neutrophils, monocytes, eosinophils, lymphocytes, CD4+cells, CD8α+cells, B cells, γδ T cells and CD11R1+Natural killer (NK) cells. CD4+, γδ T cells and CD11R1+cells were subdivided into subpopulations that were positive or negative for the CD8α marker, and conventional CD8αhigh+cytotoxic T cells were also determined. Pigs were tested underad libitumfeeding conditions from 14 to 24 weeks, and immune traits were assessed at ages 18 and 24 weeks. Line differences were estimated using residual maximum likelihood techniques. Consistent differences in immune trait levels were evident between pigs previously selected for high and low lean growth under restricted feeding: at age 24 weeks, high line pigs had higher basal levels of WBC (39·6v. 27·8×106cells per ml, s.e.d. 2·09, for highv. low line pigs) mainly explained by higher levels of lymphocytes (25·5v. 17·3×106cells per ml, s.e.d. 1·54, for highv. low line pigs) with increased numbers of CD8α+cells (8·19v. 5·15×106cells per ml, s.e.d. 0·14) and CD11R1+cells (5·23v. 2·46×106cells per ml, s.e.d. 0·43), predominantly the CD11R1+CD8α?subpopulation ((3·20v. 1·64×106cells per ml, s.e.d. 0·11). High line pigs also had increased numbers of monocytes (2·64v. 1·83×106cells per ml, s.e.d. 0·35). Similar results were obtained at age 18 weeks. There were no consistent differences between divergent lines in pigs selected for lean growth underad libitumfeeding or food intake. This is the first report to demonstrate that selection for some aspects of performance can influence WBC and leukocyte subset numbers in pigs.

Associations of acute phase protein levels with growth performance and with selection for growth performance in Large White pigs

Abstract Acute phase proteins (APP) are released into the circulation in mammals upon infection and may be used to diagnose the health status of managed populations of animals such as pigs. The current study determines APP levels in a population of apparently healthy Large White pigs from a single farm, to address two questions: (1) whether phenotypic associations can be observed between productivity and APP, indicating the effects of possible subclinical infections and (2) whether previous selection for either food intake or ‘lean growth under restricted feeding’ influences APP levels. The APP investigated were alpha1- acid glycoprotein (AGP) and haptoglobin. The APP were measured at 18 and 24 weeks of age in pigs previously selected for high lean growth (no. = 31), low lean growth (no. = 38), high daily food intake (no. = 24) and low daily food intake (no. = 26), but performing under ad libitum feeding conditions. Performance traits and APP levels were constant over the experimental period, indicating that the farm health status did not vary over time. Performance traits and APP were recorded on 119 pigs, of which 80 had both APP and performance measurements. Multiple regression analyses were used to investigate phenotypic relationships between performance traits and APP levels. Plasma concentrations of AGP were higher in 18-week-old pigs compared with 24-week-old pigs (P< 0·01) whereas haptoglobin levels did not vary according to age. Significant sex differences in APP levels were observed. Females had higher circulating levels of AGP than males at both 18 weeks and 24 weeks. Females also had higher levels of haptoglobin at 18 weeks. Levels of AGP had significant negative correlations with daily weight gain (−0·59,P< 0·01 and −0·48,P< 0·05 at 18 and 24 weeks respectively) and with daily food intake (−0·53,P< 0·01 and −0·38,P< 0·05 at 18 and 24 weeks respectively). At age 24 weeks, haptoglobin was negatively correlated with both daily weight gain (−0·35,P< 0·05) and food efficiency (−0·34,P< 0·05). Pigs selected for high lean growth under restricted feeding had higher AGP levels than pigs selected for low lean growth under restricted feeding at 18 (593v. 332 μg/ml,P< 0·01) and 24 weeks of age (313 v. 219 μg/ml,P< 0·05). Selection for daily food intake did not consistently affect AGP levels, and neither selection criteria influenced plasma haptoglobin concentrations. To conclude, we have demonstrated that amongst contemporaneous pigs of the same genotype, higher systemic AGP levels and, to a lesser extent, higher haptoglobin levels are associated with decreased performance, and that genetic selection for ‘efficient lean growth under restricted feeding’ can increase serum AGP levels.

Development of an anti-porcine CD34 monoclonal antibody that identifies hematopoietic stem cells

OBJECTIVES

The isolation of porcine hematopoietic stem cells (HSC) would be an important step toward development of porcine-to-human chimerism for induction of tolerance in clinical xenotransplantation. CD34 is a common marker of HSC and has not been developed as a marker in pigs. In this study we have generated and characterized a monoclonal antibody (mAb) that identifies porcine CD34 on a subset of porcine bone marrow (BM) stem/progenitor cells.

METHODS

The porcine CD34 gene was cloned and a recombinant protein produced. An anti-porcine CD34 mAb was produced that could detect both the recombinant protein and a subset of porcine BM cells. The CD34(+) cells were phenotyped by lineage and HSC associated markers. Furthermore, the CD34(+) cells were analyzed by colony-forming unit (CFU) assay.

RESULTS

Two splice variants of the porcine CD34 gene were cloned and a recombinant protein produced for mAb production. The mAb developed can detect both the recombinant protein and the native CD34 protein on a range of pig tissues, including BM. This subset of BM cells was negative for hematopoietic lineage makers, including CD3, CD14, and CD21 and positive for other known porcine HSC markers, including CD90, CD172a, histocompatibility complex (MHC) class I, and MHC class II. Moreover, the CD34(+) BM cells were enriched for multilineage progenitor cells as determined by CFU assay.

CONCLUSIONS

Similar to human and mouse CD34, pig CD34 detects a subset of BM progenitor cells. This mAb will now provide a means for isolating porcine CD34(+) cells to be further analyzed for HSC activity and to assess their potential to develop pig-to-human chimeras to induce xenograft tolerance.

Perforin expression can define CD8 positive lymphocyte subsets in pigs allowing phenotypic and functional analysis of natural killer, cytotoxic T, natural killer T and MHC un-restricted cytotoxic T-cells

In this study we have used the expression of perforin to characterize subsets of porcine cytotoxic lymphocytes. Perforin positive lymphocytes expressed both CD2 and CD8alpha, most were small dense lymphocytes (SDL) and up to 90% were CD3 negative. However, the numbers of perforin positive T-cells increased with the age of the animal and their populations increased after specific antigen stimulation in vitro. The remaining perforin positive lymphocytes were large and granular and contained more CD3+CD5+CD6+ T-cells (-40%) of which a substantial proportion also co-expressed CD4. Perforin was expressed in subpopulations of both CD8alphaalpha and CD8alphabeta lymphocytes, but was not expressed in gammadelta T-cells or monocyte/macrophages. The perforin positive CD3- subset was phenotypically homogeneous and defined as CD5-CD6-CD8beta-CD16+CD11b+. This population had NK activity and expressed mRNA for the NK receptor NKG2D, and adaptors DAP10 and DAP12. Perforin positive T-cells (CD3+) could be divided into at least three subsets. The first subset was CD4-CD5+CD6+CD11b-CD16- most were small dense lymphocytes with cytotoxic T-cell activity but not all expressed CD8beta. The second subset was mainly observed in the large granular lymphocytes. Their phenotype was CD4+CD5+CD6+CD8beta+CD16-CD11b- and also showed functional CTL activity. Thus not all of double positive T-cells are memory helper T-cells. The third subset did not express the T-cell co-receptor CD6, but up to half of them expressed another T-cell co-receptor CD5. The majority of this subset expressed CD11b and CD16, thus the third perforin positive T-cell subset was CD3+CD4-CD5+CD6-CD8beta+/-CD11b+CD16+, and possessed MHC-unrestricted cytotoxicity and LAK activity.

Summary of the animal homologue section of HLDA8

Development of reagents against leukocyte differentiation antigens in veterinary immunology is slower compared to humans and mice. Cross-reactivity studies with monoclonal antibodies (mAb) generated against human molecules represent an excellent approach for the detection of new reagents for the minor characterised species. Three hundred seventy-seven commercially available mAb from different companies were tested for their reactivity with cells from 17 species--including non-human primates, ruminants, swine, horse, carnivores, rabbit, guinea pig, chicken and fish. In a first round of testing by flow cytometry (FCM) 182 mAb showed reactivity with atleast one of the species described above. Most of the cross-reactivity was found against non-human primate leukocytes, but also species in evolutionarily more distant from humans showed in some cases a clear staining pattern in flow cytometry (FCM). In a second round these FCM-results were confirmed by molecular analyses, by immunoprecipitation studies and analyses on transfectants. Interesting was the broad species-overlapping reactivity of mAb directed against CD9 (11 out of 17 species), CD11a (11/17), CD14 (11/17), CD18 (13/17), CD21 (7/17), CD29 (10/17), CD44 (13/17), CD45 (9/17), CD47 (10/17), and CD49d (13/17), CD61 (6/17), CD86 (7/17), CD91 (5/17), and CD172a (10/17), indicating evolutionary highly conserved epitopes on these surface molecules. Our results suggest the suitability of crossreactive mAb for the animal model studies. Moreover, these findings contribute to our understanding of the evolution of the immune system.

Innate immune traits differ between Meishan and Large White pigs

A panel of innate immune traits were compared between Meishan and Large White pigs. These pigs were of similar age and kept under the same environmental conditions to reduce non-genetically derived variation in immune traits. The animals were all apparently healthy and were not experimentally challenged with any pathogen during the study. The measures only required a small blood sample. Total white cell counts were similar between the pig breeds. However, the numbers of lymphocytes, neutrophils and monocytes differed significantly, with Meishans having higher neutrophil and monocyte counts and lower lymphocyte counts. Flow cytometric methods were used to determine quantitatively the characteristics and function of neutrophils and monocytes. Meishan neutrophils were smaller and less complex than Large White neutrophils, and phagocytosis of Escherichia coli and the ensuing oxidative burst was lower in Meishan neutrophils compared to Large White neutrophils. Monocyte phagocytosis of E. coli was significantly less than that of neutrophils in both breeds but the function of Meishan monocytes as measured by phagocytosis and tumour necrosis factor alpha (TNFalpha) release did not differ from that of Large White monocytes. Levels of acute phase proteins also differed between the breeds with a significantly higher proportion of Meishans having elevated serum amyloid A levels. However, Meishans had lower alpha(1)-acid glycoprotein levels than Large Whites and haptoglobin levels were similar. Such differences in innate immune traits may have implications in the resistance to infection by a broad range of pathogens and subsequent disease effects in these breeds. Further studies are warranted to investigate the genes underlying these traits.

Use of CD9 expression to enrich for porcine hematopoietic progenitors

OBJECTIVE

The aim of this study was to develop novel markers for enrichment of hematopoietic progenitors from bone marrow of swine.

MATERIALS AND METHODS

We previously showed that pig bone marrow contains a "side population" (SP) of Hoechst dye-effluxing cells that resembles the hematopoietic stem cell (HSC)-containing murine SP and therefore represents a putative pig stem cell population. We screened a panel of monoclonal antibodies for those that allowed positive or negative enrichment of porcine SP cells and tested one of these for enrichment of hematopoietic progenitors in short-term and long-term in vitro assays. We then screened an expression library to clone the gene whose product is recognized by this antibody.

RESULTS

Among a panel of 35 monoclonal lines screened, we found three that were useful for positive enrichment of SP cells and seven for negative enrichment. The 4-6 monoclonal line, allowing around 10-fold negative enrichment of SP cells, recognized the product of the porcine CD9 gene. Hematopoietic progenitors measured by short-term colony-forming unit and long-term cobblestone area-forming cell assays were around 10-fold enriched in the CD9(negative/low) fraction and were significantly depleted in the CD9(high) fraction.

CONCLUSIONS

The antibody against the porcine CD9 gene product may be of use for enrichment of porcine hematopoietic stem cells. This approach to identify novel markers for enrichment of hematopoietic progenitors may be applicable to other mammalian species.

Evaluation of natural killer cell recruitment to embryonic attachment sites during early porcine pregnancy

Specialized natural killer (NK) lymphocytes are a feature of the pregnant uterus in humans and rodents. Conceptus-mediated recruitment of uterine (u)NK cells in the pig was proposed based on evidence that elevated uNK activity was temporally associated with increased leukocyte density in endometrium underlying conceptuses. The objective of this study was to determine whether uNK cells were more abundant at embryonic attachment sites during the early postattachment period. Mononuclear leukocytes were isolated from endometrium at attachment sites versus between attachment sites, and expression of CD16, a marker for NK cells, was assessed by flow cytometry. CD16 binding was normalized to leukocyte numbers in each sample. CD16+ small lymphocytes were more frequent in uterus than in blood (41% +/- 2% versus 26% +/- 4%). Differences between pregnant and luteal phase uterus (43% +/- 2% versus 31% +/- 7%, respectively) were not statistically significant. In pregnant animals, CD16+ lymphocytes were slightly but significantly more abundant in uterus at attachment sites versus between attachment sites at Days 15-17, 21-22, and 25-28. Before normalization, CD16+ large, granular cells were more abundant at attachment sites versus between attachment sites; however, these differences were removed when data were normalized according to leukocyte numbers. Further characterization showed that the proportion of large granular leukocytes expressing CD8, reactive with NK cells and T cell subsets, was 2-fold higher in pregnant uterus than in maternal blood. These results raise the possibility that uNK cells resembling those in blood may be transformed into larger, more granulated forms in the uterine microenvironment.