Comparative gene expression by WC1 + γδ and CD4 + αβ T lymphocytes, which respond to Anaplasma marginale , demonstrates higher expression of chemokines and other myeloid cell‐associated genes by WC1 + γδ T cells

Advantages and Challenges of Differential Immune Cell Count Determination in Blood and Milk for Monitoring the Health and Well-Being of Dairy Cows

A key challenge of the 21st century will be to provide the growing world population with a sustainable and secure supply of food. Consequently, the dairy farming’s primary task is to lower milk losses and other inefficiencies associated with diseased cows. Moreover, a shift from curative to preventive health management would be desirable for mastitis and a wide variety of other infectious and non-infectious cattle diseases, some of which are known to have profound negative effects on the performance and well-being of cows. Differential cell counting (DCC), a procedure that aims to determine the proportions of different somatic cell types in raw milk samples, has not only the potential to optimize mastitis diagnostics, but it could furthermore serve as a diagnostic tool for monitoring the general and overall health status of dairy cows. Based on a broad search of the literature, the practical utility of various types of DCC is summarized and discussed in this review. Since it might be of advantage to interpret DCC with the aid of data from studies in humans, differences between the immune systems of humans and dairy cattle, with a special focus on surface marker expression profiles and γδ (gamma delta) T-cell characteristics, are also described.

Defining the caprine γδ T cell WC1 multigenic array and evaluation of its expressed sequences and gene structure conservation among goat breeds and relative to cattle

Workshop cluster 1 (WC1) molecules are part of the scavenger receptor cysteine-rich (SRCR) superfamily and act as hybrid co-receptors for the γδ T cell receptor and as pattern recognition receptors for binding pathogens. These members of the CD163 gene family are expressed on γδ T cells in the blood of ruminants. While the presence of WC1⁺ γδ T cells in the blood of goats has been demonstrated using monoclonal antibodies, there was no information available about the goat WC1 gene family. The caprine WC1 multigenic array was characterized here for number, structure and expression of genes, and similarity to WC1 genes of cattle and among goat breeds. We found sequence for 17 complete WC1 genes and evidence for up to 30 SRCR a1 or d1 domains which represent distinct signature domains for individual genes. This suggests substantially more WC1 genes than in cattle. Moreover, goats had seven different WC1 gene structures of which 4 are unique to goats. Caprine WC1 genes also had multiple transcript splice variants of their intracytoplasmic domains that eliminated tyrosines shown previously to be important for signal transduction. The most distal WC1 SRCR a1 domains were highly conserved among goat breeds, but fewer were conserved between goats and cattle. Since goats have a greater number of WC1 genes and unique WC1 gene structures relative to cattle, goat WC1 molecules may have expanded functions. This finding may impact research on next-generation vaccines designed to stimulate γδ T cells.

Transcriptional programming and gene regulation in WC1+ γδ T cell subpopulations

γδ T cells represent a high proportion of lymphocytes in the blood of ruminants with the majority expressing lineage-specific glycoproteins from the WC1 family. WC1 receptors are coded for by a multigenic array whose genes have variegated but stable expression among cells in the γδ T cell population. WC1 molecules function as hybrid pattern recognition receptors as well as co-receptors for the TCR and are required for responses by the cells. Because of the variegated gene expression, WC1⁺ γδ T cells can be divided into two main populations known as WC1.1⁺ and WC1.2⁺ based on monoclonal antibody reactivity with the expressed WC1 molecules. These subpopulations differ in their ability to respond to specific pathogens. Here, we showed these populations are established in the thymus and that WC1.1⁺ and WC1.2⁺ subpopulations have transcriptional programming that is consistent with stratification towards Tγδ1 or Tγδ17. WC1.1⁺ cells exhibited the Tγδ1 phenotype with greater transcription of Tbx21 and production of more IFNγ while the WC1.2⁺ subpopulation tended towards Tγδ17 programming producing higher levels of IL-17 and had greater transcription of Rorc. However, when activated both WC1⁺ subpopulations' cells transcribed Tbx21 and secreted IFNγ and IL-17 reflecting the complexity of these subpopulations defined by WC1 gene expression. The gene networks involved in development of these two subpopulations including expression of their archetypal genes wc1-3 (WC1.1⁺) and wc1-4 (WC1.2⁺) were unknown but we report that SOX-13, a γδ T cell fate-determining transcription factor, has differential occupancy on these WC1 gene loci and suggest a model for development of these subpopulations.

Subpopulations of swine γδ T cells defined by TCRγ and WC1 gene expression

γδ T cells constitute a major portion of lymphocytes in the blood of both ruminants and swine. Subpopulations of swine γδ T cells have been distinguished by CD2 and CD8α expression. However, it was not clear if they have distinct expression profiles of their T-cell receptor (TCR) or WC1 genes. Identifying receptor expression will contribute to understanding the functional differences between these subpopulations and their contributions to immune protection. Here, we annotated three genomic assemblies of the swine TCRγ gene locus finding four gene cassettes containing C, J and V genes, although some haplotypes carried a null TRGC gene (TRGC4). Genes in the TRGC1 cassette were homologs of bovine TRGC5 cassette while the others were not homologous to bovine genes. Here we evaluated three principal populations of γδ T cells (CD2⁺/SWC5^-, CD2^-/SWC5⁺, and CD2^-/SWC5^-). Both CD2^- subpopulations transcribed WC1 co-receptor genes, albeit with different patterns of gene expression but CD2⁺ cells did not. All subpopulations transcribed TCR genes from all four cassettes, although there were differences in expression levels. Finally, the CD2⁺ and CD2^- γδ T-cell populations differed in their representation in various organs and tissues, presumably at least partially reflective of different ligand specificities for their receptors.

Activated γδ T Cells With Higher CD107a Expression and Inflammatory Potential During Early Pregnancy in Patients With Recurrent Spontaneous Abortion

Previous studies have reported the involvement of γδ T cells in recurrent spontaneous abortion (RSA); however, both pathogenic and protective effects were suggested. To interrogate the role of γδ T cells in RSA, peripheral blood from RSA patients and healthy women with or without pregnancy were analyzed for γδ T cells by flow cytometry (n = 9–11 for each group). Moreover, the decidua from pregnant RSA patients and healthy controls (RSA-P and HC-P group, respectively) was simultaneously stained for γδ T cells by immunohistochemistry (IHC) and bulk sequenced for gene expression. Our results demonstrated that the frequencies of peripheral γδ T cells and their subpopulations in RSA patients were comparable to that in healthy subjects, but the PD1 expression on Vδ2⁺ cells was increased in pregnant patients. Furthermore, peripheral Vδ2⁺ cells in RSA-P patients demonstrated significantly increased expression of CD107a, as compared to that in pregnant healthy controls. In addition, RSA-P patients had higher proportion of IL-17A-secreting but not IL-4-secreting Vδ2⁺ cells compared to the control groups. In decidua, an inflammatory microenvironment was also evident in RSA-P patients, in which CCL8 expression and the infiltration of certain immune cells were higher than that in the HC-P group, as revealed by transcriptional analysis. Finally, although the presence of γδ T cells in decidua could be detected during pregnancy in both RSA patients and healthy subjects by multicolor IHC analysis, the expression of CD107a on γδ T cells was markedly higher in the RSA-P group. Collectively, our results indicated that the increased activation, cytotoxicity, and inflammatory potential of peripheral and/or local γδ T cells might be responsible for the pathogenesis of RSA. These findings could provide a better understanding of the role of γδ T cells in RSA and shed light on novel treatment strategies by targeting γδ T cells for RSA patients.

Gamma Delta TCR and the WC1 Co-Receptor Interactions in Response to Leptospira Using Imaging Flow Cytometry and STORM

The WC1 cell surface family of molecules function as hybrid gamma delta (γδ) TCR co-receptors, augmenting cellular responses when cross-linked with the TCR, and as pattern recognition receptors, binding pathogens. It is known that following activation, key tyrosines are phosphorylated in the intracytoplasmic domains of WC1 molecules and that the cells fail to respond when WC1 is knocked down or, as shown here, when physically separated from the TCR. Based on these results we hypothesized that the colocalization of WC1 and TCR will occur following cellular activation thereby allowing signaling to ensue. We evaluated the spatio-temporal dynamics of their interaction using imaging flow cytometry and stochastic optical reconstruction microscopy. We found that in quiescent γδ T cells both WC1 and TCR existed in separate and spatially stable protein domains (protein islands) but after activation using Leptospira, our model system, that they concatenated. The association between WC1 and TCR was close enough for fluorescence resonance energy transfer. Prior to concatenating with the WC1 co-receptor, γδ T cells had clustering of TCR-CD3 complexes and exclusion of CD45. γδ T cells may individually express more than one variant of the WC1 family of molecules and we found that individual WC1 variants are clustered in separate protein islands in quiescent cells. However, the islands containing different variants merged following cell activation and before merging with the TCR islands. While WC1 was previously shown to bind Leptospira in solution, here we showed that Leptospira bound WC1 proteins on the surface of γδ T cells and that this could be blocked by anti-WC1 antibodies. In conclusion, γδ TCR, WC1 and Leptospira interact directly on the γδ T cell surface, further supporting the role of WC1 in γδ T cell pathogen recognition and cellular activation.

Tick extracellular vesicles enable arthropod feeding and promote distinct outcomes of bacterial infection

Extracellular vesicles are thought to facilitate pathogen transmission from arthropods to humans and other animals. Here, we reveal that pathogen spreading from arthropods to the mammalian host is multifaceted. Extracellular vesicles from Ixodes scapularis enable tick feeding and promote infection of the mildly virulent rickettsial agent Anaplasma phagocytophilum through the SNARE proteins Vamp33 and Synaptobrevin 2 and dendritic epidermal T cells. However, extracellular vesicles from the tick Dermacentor andersoni mitigate microbial spreading caused by the lethal pathogen Francisella tularensis. Collectively, we establish that tick extracellular vesicles foster distinct outcomes of bacterial infection and assist in vector feeding by acting on skin immunity. Thus, the biology of arthropods should be taken into consideration when developing strategies to control vector-borne diseases.

Goat γδ T cell subpopulations defined by WC1 expression, responses to pathogens and cytokine production

The major functions of γδ T cells in mammals overlap with those of αβ T cells but differ in that γδ T cells are rapid responders and see different types of antigens. While γδ T cells have been shown to be a major population of circulating lymphocytes in artiodactyl species such as cattle, sheep, and pigs, less is known about these cells in goats, an important agricultural species. We have recently shown that WC1, a γδ T cell-specific family of hybrid pattern recognition receptors/co-receptors, is a multigenic family in goats expanded beyond what occurs in cattle. This study was conducted to address some of the limitations of previous studies in determining the proportions of γδ T cells, WC1⁺ γδ T cells as well as the WC1.1⁺ and WC1.2⁺ subpopulations in blood and to evaluate their responses to various pathogens. Previously, the proportion of caprine γδ T cells was determined using a monoclonal antibody (mAb) 86D that we show here does not react with all γδ T cells thereby underestimating their contribution to the lymphocyte population. Using a mAb reactive with the TCRδ constant region we found the proportion of γδ T cells in blood was not significantly less than that of either CD4 or CD8 T cells and did not decrease with age after 6 months. γδ T cells that expressed WC1 ranged from ~20 to 85% of the total γδ T cells. Less than half of those were classified as WC1.1⁺ or WC1.2⁺ by mAb staining thus indicating a third major WC1⁺ population. We found that naïve γδ T cells proliferated in cultures of PBMC stimulated with antigens of Leptospira or Mycobacterium avium paratuberculosis (MAP) more than they did in control medium cultures or in those stimulated with M. bovis BCG antigens and that the responding γδ T cells included both WC1⁺ and WC1^- cells. In ex vivo PMA/ionomycin-stimulated cultures of WC1^- γδ T cells but not WC1⁺ cells produced both IL-17 and IFNγ. In longterm cultures with Leptospira or MAP both WC1^- and WC1⁺ cells proliferated but only WC1^- γδ T cells produced IL-17. In conclusion, goats have a substantial number of WC1^- and WC1⁺ γδ T cells in PBMC that do not decrease with animal age after 6 months; both populations respond to bacterial antigens as naïve cells but in these cultures only the WC1^- γδ cells produc IL-17 and IFNγ .

Special features of γδ T cells in ruminants

Ruminant γδ T cells were discovered in the mid-1980's shortly after a novel T cell receptor (TCR) gene from murine cells was described in 1984 and the murine TCRγ gene locus in 1985. It was possible to identify γδ T cell populations early in ruminants because they represent a large proportion of the peripheral blood mononuclear cells (PBMC). This null cell population, γδ T cells, was designated as such by its non-reactivity with monoclonal antibodies (mAb) against ovine and bovine CD4, CD8 and surface immunoglobulin (Ig). γδ T cells are non-conventional T cells known as innate-like cells capable of using both TCR as well as other types of receptor systems including pattern recognition receptors (PRR) and natural killer receptors (NKR). Bovine γδ T cells have been shown to respond to stimulation through toll-like receptors, NOD, and NKG2D as well as to cytokines alone, protein and non-protein antigens through their TCR, and to pathogen-infected host cells. The two main populations of γδ T cells are distinguished by the presence or absence of the hybrid co-receptor/PRR known as WC1 or T19. These two populations not only differ by their proportional representation in various tissues and organs but also by their migration into inflamed tissues. The WC1⁺ cells are found in the blood, skin and spleen while the WC1^- γδ T cells predominate in the gut, mammary gland and uterus. In ruminants, γδ T cells may produce IFNγ, IL-17, IL-10 and TGFβ, have cytotoxic activity and memory responses. The expression of particular WC1 family members controls the response to particular pathogens and correlates with differences in cytokine responses. The comparison of the WC1 gene families in cattle, sheep and goats is discussed relative to other multigenic arrays that differentiate γδ T cells by function in humans and mice.

Fucoidan from seaweed Fucus vesiculosus inhibits 2,4-dinitrochlorobenzene-induced atopic dermatitis

Fucoidan, one activator of scavenger receptor class A (SR-A), plays important roles in a variety of biological activities, including anti-inflammatory, antioxidant, and antitumor actions. However, the effects of fucoidan on atopic dermatitis (AD) have not been elucidated. To assess this, 2,4-dinitrofluorobenzene (DNFB)-treated BALB/c mice were painted with fucoidan. Results showed that fucoidan significantly ameliorated ear swelling, improved abdomen skin lesions, and decreased inflammatory cell infiltration. In addition, fucoidan significantly suppressed the serum levels of IgE and IL-4 in DNFB-induced AD mice. The infiltration of CD4+ T cells in skin lesions and spleen was also reduced in fucoidan-treated AD mice. Furthermore, treatment with fucoidan promoted Treg cells but attenuated Th1/17 response in the spleens from DNFB-induced AD mice. Together, these results suggest that fucoidan, a natural seaweed-rich polysaccharide, has a potential therapeutic efficacy in the treatment of AD, correlates with the induction of higher anti-inflammatory response through inducing Treg cells.

Brucella canis induces canine CD4+ T cells multi-cytokine Th1/Th17 production via dendritic cell activation

Brucella canis is a small intracellular Gram-negative bacterium that frequently leads to chronic infections highly resistant to antibiotic therapy in dogs. Also, it causes mild human brucellosis compared to other zoonotic Brucella spp. Herein we characterize the cellular immune response elicited by B. canis by analysing human and canine CD4⁺ T cells after stimulation with autologous monocyte-derived dendritic cells (MoDCs). Human and canine B. canis-primed MoDCs stimulated autologous CD4⁺ T cells; however, a Th1 response was triggered by human MoDCs, whereas canine MoDCs induced Th1/Th17 responses, with increased CD4⁺ T cells producing IFN-γ and IL-17A simultaneously. Each pattern of cellular response may contribute to host susceptibility, helping to understand the differences in B. canis virulence between these two hosts. In addition, other aspects of canine immunology are unveiled by highlighting the participation of IL-17A-producing canine MoDCs and CD4⁺ T cells producing IFN-γ and IL-17A.

Local immune response to larvae of Rhipicephalus microplus in Santa Gertrudis cattle

This study investigated the local immune response at larval attachment sites in Santa Gertrudis cattle with low and high levels of tick resistance. Skin samples with tick larvae attached were collected from Santa Gertrudis cattle at the end of a period of 25 weekly infestations, when the animals manifested highly divergent tick-resistant phenotypes. There was a tendency for more CD3⁺ , CD4⁺ , CD8⁺ , CD25⁺ , γδ T cells and neutrophils to concentrate at larval tick attachment site in susceptible cattle than in resistant cattle but the differences were significant only for γδ T cells and CD4⁺ cells. Most of the cattle developed intra-epidermal vesicles at the larval attachment site but the predominant cell within or around the vesicles was the neutrophil in susceptible animals and eosinophil in the resistant animals. The monoclonal antibodies (mAbs) specific for CD45 and CD45 RO antigens reacted with skin leucocytes from a higher number of susceptible cattle than resistant cattle. Our data suggest that some of the cellular responses mounted at larval attachment site are not involved in tick protection. The mAbs specific for CD45 and CD45 RO directly, or a test for CD45 genotype might be developed as markers of tick susceptibility or resistance.

Measuring bovine γδ T cell function at the site of Mycobacterium bovis infection

Bovine γδ T cells are amongst the first cells to accumulate at the site of Mycobacterium bovis infection; however, their role in the developing lesion remains unclear. We utilized transcriptomics analysis, in situ hybridization, and a macrophage/γδ T cell co-culture system to elucidate the role of γδ T cells in local immunity to M. bovis infection. Transcriptomics analysis revealed that γδ T cells upregulated expression of several novel, immune-associated genes in response to stimulation with M. bovis antigen. BCG-infected macrophage/γδ T cell co-cultures confirmed the results of our RNAseq analysis, and revealed that γδ T cells from M. bovis-infected animals had a significant impact on bacterial viability. Analysis of γδ T cells within late-stage M. bovis granulomas revealed significant expression of IFN-γ and CCL2, but not IL-10, IL-22, or IL-17. Our results suggest γδ T cells influence local immunity to M. bovis through cytokine secretion and direct effects on bacterial burden.

Prophylactic orthosteric inhibition of leukocyte integrin CD11b/CD18 prevents long-term fibrotic kidney failure in cynomolgus monkeys

Ischaemic acute kidney injury (AKI), an inflammatory disease process, often progresses to chronic kidney disease (CKD), with no available effective prophylaxis. This is in part due to lack of clinically relevant CKD models in non-human primates. Here we demonstrate that inhibition of the archetypal innate immune receptor CD11b/CD18 prevents progression of AKI to CKD in cynomolgus monkeys. Severe ischaemia-reperfusion injury of the right kidney, with subsequent periods of the left ureter ligation, causes irreversible right kidney failure 3, 6 or 9 months after AKI. Moreover, prophylactic inactivation of CD11b/CD18, using the orthosteric CD11b/CD18 inhibitor mAb107, improves microvascular perfusion and histopathology, reduces intrarenal pro-inflammatory mediators and salvages kidney function long term. These studies reveal an important early role of CD11b⁺ leukocytes in post-ischaemic kidney fibrosis and failure, and suggest a potential early therapeutic intervention to mitigate progression of ischaemic AKI to CKD in humans.

Biology and structure of leukocyte β 2 integrins and their role in inflammation

Integrins comprise a large family of αβ heterodimeric cell adhesion receptors that are expressed on all cells except red blood cells and that play essential roles in the regulation of cell growth and function. The leukocyte integrins, which include members of the β ₁, β ₂, β ₃, and β ₇ integrin family, are critical for innate and adaptive immune responses but also can contribute to many inflammatory and autoimmune diseases when dysregulated. This review focuses on the β ₂ integrins, the principal integrins expressed on leukocytes. We review their discovery and role in host defense, the structural basis for their ligand recognition and activation, and their potential as therapeutic targets.

The bovine model for elucidating the role of γδ T cells in controlling infectious diseases of importance to cattle and humans

There are several instances of co-investigation and related discoveries and achievements in bovine and human immunology; perhaps most interesting is the development of the BCG vaccine, the tuberculin skin test and the more recent interferon-gamma test that were developed first in cattle to prevent and diagnosis bovine tuberculosis and then applied to humans. There are also a number of immune-physiological traits that ruminant share with humans including the development of their immune systems in utero which increases the utility of cattle as a model for human immunology. These are reviewed here with a particular focus on the use of cattle to unravel γδ T cell biology. Based on the sheer number of γδ T cells in this γδ T cell high species, it is reasonable to expect γδ T cells to play an important role in protective immune responses. For that reason alone cattle may provide good models for elucidating at least some of the roles γδ T cells play in protective immunity in all species. This includes fundamental research on γδ T cells as well as the responses of ruminant γδ T cells to a variety of infectious disease situations including to protozoan and bacterial pathogens. The role that pattern recognition receptors (PRR) play in the activation of γδ T cells may be unique relative to αβ T cells. Here we focus on that of the γδ T cell specific family of molecules known as WC1 or T19 in ruminants, which are part of the CD163 scavenger receptor cysteine rich (SRCR) family that includes SCART1 and SCART2 expressed on murine γδ T cells. We review the evidence for WC1 being a PRR as well as an activating co-receptor and the role that γδ T cells bearing these receptors play in immunity to leptospirosis and tuberculosis. This includes the generation of memory responses to vaccines, thereby continuing the tradition of co-discovery between cattle and humans.

Bovine γδ T cells are a major regulatory T cell subset

In humans and mice, γδ T cells represent <5% of the total circulating lymphocytes. In contrast, the γδ T cell compartment in ruminants accounts for 15–60% of the total circulating mononuclear lymphocytes. Despite the existence of CD4⁺CD25^high Foxp3⁺ T cells in the bovine system, these are neither anergic nor suppressive. We present evidence showing that bovine γδ T cells are the major regulatory T cell subset in peripheral blood. These γδ T cells spontaneously secrete IL-10 and proliferate in response to IL-10, TGF-β, and contact with APCs. IL-10–expressing γδ T cells inhibit Ag-specific and nonspecific proliferation of CD4⁺ and CD8⁺ T cells in vitro. APC subsets expressing IL-10 and TFG-β regulate proliferation of γδ T cells producing IL-10. We propose that γδ T cells are a major regulatory T cell population in the bovine system.

Differential chemokine and cytokine production by neonatal bovine γδ T-cell subsets in response to viral toll-like receptor agonists and in vivo respiratory syncytial virus infection

γδ T cells respond to stimulation via toll-like receptors (TLR). Bovine γδ T cells express TLR3 and TLR7, receptors that are key for the recognition of viruses such as bovine respiratory syncytial virus (BRSV); however, responses of γδ T cells to stimulation via these receptors, and their role during viral infections, remains unclear. Here, we demonstrate that neonatal bovine γδ T cells exhibit robust chemokine and cytokine production in response to the TLR3 agonist, Poly(I:C), and the TLR7 agonist, Imiquimod. Importantly, we observe a similar phenotype in γδ T-cell subsets purified from calves infected with BRSV. Bovine γδ T cells are divided into subsets based upon their expression of WC1, and the response to TLR stimulation and viral infection differs between these subsets, with WC1.1(+) and WC1(neg) γδ T cells producing macrophage inflammatory protein-1α and granulocyte-macrophage colony-stimulating factor, and WC1.2(+) γδ T cells preferentially producing the regulatory cytokines interleukin-10 and transforming growth factor-β. We further report that the active vitamin D metabolite 1,25-dihydroxyvitamin D3 does not alter γδ T-cell responses to TLR agonists or BRSV. To our knowledge, this is the first characterization of the γδ T-cell response during in vivo BRSV infection and the first suggestion that WC1.1(+) and WC1(neg) γδ T cells contribute to the recruitment of inflammatory populations during viral infection. Based on our results, we propose that circulating γδ T cells are poised to rapidly respond to viral infection and suggest an important role for γδ T cells in the innate immune response of the bovine neonate.

Comparative biology of γδ T cell function in humans, mice, and domestic animals

γδ T cells are a functionally heterogeneous population and contribute to many early immune responses. The majority of their activity is described in humans and mice, but the immune systems of all jawed vertebrates include the γδ T cell lineage. Although some aspects of γδ T cells vary between species, critical roles in early immune responses are often conserved. Common features of γδ T cells include innate receptor expression, antigen presentation, cytotoxicity, and cytokine production. Herein we compare studies describing these conserved γδ T cell functions and other, potentially unique, functions. γδ T cells are well documented for their potential immunotherapeutic properties; however, these proposed therapies are often focused on human diseases and the mouse models thereof. This review consolidates some of these studies with those in other animals to provide a consensus for the current understanding of γδ T cell function across species.

Gene number determination and genetic polymorphism of the gamma delta T cell co-receptor WC1 genes

Background

WC1 co-receptors belong to the scavenger receptor cysteine-rich (SRCR) superfamily and are encoded by a multi-gene family. Expression of particular WC1 genes defines functional subpopulations of WC1⁺ γδ T cells. We have previously identified partial or complete genomic sequences for thirteen different WC1 genes through annotation of the bovine genome Btau_3.1 build. We also identified two WC1 cDNA sequences from other cattle that did not correspond to sequences in the Btau_3.1 build. Their absence in the Btau_3.1 build may have reflected gaps in the genome assembly or polymorphisms among animals. Since the response of γδ T cells to bacterial challenge is determined by WC1 gene expression, it was critical to understand whether individual cattle or breeds differ in the number of WC1 genes or display polymorphisms.

Results

Real-time quantitative PCR using DNA from the animal whose genome was sequenced (“Dominette”) and sixteen other animals representing ten breeds of cattle, showed that the number of genes coding for WC1 co-receptors is thirteen. The complete coding sequences of those thirteen WC1 genes is presented, including the correction of an error in the WC1-2 gene due to mis-assembly in the Btau_3.1 build. All other cDNA sequences were found to agree with the previous annotation of complete or partial WC1 genes. PCR amplification and sequencing of the most variable N-terminal SRCR domain (domain 1 which has the SRCR “a” pattern) of each of the thirteen WC1 genes showed that the sequences are highly conserved among individuals and breeds. Of 160 sequences of domain 1 from three breeds of cattle, no additional sequences beyond the thirteen described WC1 genes were found. Analysis of the complete WC1 cDNA sequences indicated that the thirteen WC1 genes code for three distinct WC1 molecular forms.

Conclusion

The bovine WC1 multi-gene family is composed of thirteen genes coding for three structural forms whose sequences are highly conserved among individual cattle and breeds. The sequence diversity necessary for WC1 genes to function as a multi-genic pattern recognition receptor array is encoded in the genome, rather than generated by recombinatorial diversity or hypermutation.

Contribution of transcript stability to a conserved procyanidin-induced cytokine response in γδ T cells

γδ T cells function in innate and adaptive immunity and are primed for secondary responses by procyanidin components of unripe apple peel (APP). Here we investigate the effects of APP and purified procyanidins on γ δ T cell gene expression. A microarray analysis was performed on bovine γ δ T cells treated with APP; increases in transcripts encoding GM-CSF, IL-8, and IL-17, but not markers of TCR stimulation such as IFNγ , were observed. Key responses were confirmed in human, mouse, and bovine cells by RT-PCR and/or ELISA, indicating a conserved response to procyanidins. In vivo relevance of the cytokine response was shown in mice following intraperitoneal injection of APP, which induced production of CXCL1/KC and resulted in neutrophil influx to the blood and peritoneum. In the human γ δ T cell-line, MOLT-14, GM-CSF and IL-8 transcripts were increased and stabilized in cells treated with crude APP or purified procyanidins. The ERK1/2 MAPK pathway was activated in APP-treated cells, and necessary for transcript stabilization. Our data describe a unique γ δ T cell inflammatory response during procyanidin treatment and suggest that transcript stability mechanisms could account, at least in part, for the priming phenotype.

Scavenger receptor WC1 contributes to the γδ T cell response to Leptospira

WC1 molecules are exclusively expressed on the surface of γδ T cells. They belong to the scavenger receptor cysteine-rich (SRCR) superfamily and are encoded by a multi-gene family. WC1 molecules have been grouped on the basis of antibody reactivity. The expression of WC1 molecules from these serologically defined groups is correlated with differences in γδ T cell responses. The expression of receptors within the WC1.1 group correlates with the capacity of γδ T cells to respond to Leptospira antigen. In this study, we used RNA interference to directly investigate the role of WC1 expression in the response to Leptospira borgpetersenii. We found that when three out of thirteen WC1 gene products were downregulated by RNA interference, γδ T cell proliferation and IFN-γ production in response to Leptospira antigen was significantly reduced. Our data demonstrate that specific receptors in the WC1 family directly participate in Leptospira recognition and/or activation of γδ T cells.

Evolution of the CD163 family and its relationship to the bovine gamma delta T cell co-receptor WC1

Background

The scavenger receptor cysteine rich (SRCR) domain is an ancient and conserved protein domain. CD163 and WC1 molecules are classed together as group B SRCR superfamily members, along with Spα, CD5 and CD6, all of which are expressed by immune system cells. There are three known types of CD163 molecules in mammals, CD163A (M130, coded for by CD163), CD163b (M160, coded for by CD163L1) and CD163c-α (CD163L1 or SCART), while their nearest relative, WC1, is encoded by a multigene family so far identified in the artiodactyl species of cattle, sheep, and pigs.

Results

We annotated the bovine genome and identified genes coding for bovine CD163A and CD163c-α but found no evidence for CD163b. Bovine CD163A is widely expressed in immune cells, whereas CD163c-α transcripts are enriched in the WC1+ γδ T cell population. Phylogenetic analyses of the CD163 family genes and WC1 showed that CD163c-α is most closely related to WC1 and that chicken and platypus have WC1 orthologous genes, previously classified as among their CD163 genes.

Conclusion

Since it has been shown that WC1 plays an important role in the regulation of γδ T cell responses in cattle, which, like chickens, have a high percentage of γδ T cells in their peripheral blood, CD163c-α may play a similar role, especially in species lacking WC1 genes. Our results suggest that gene duplications resulted in the expansion of CD163c-α-like and WC1-like molecules. This expanded repertoire was retained by species known as "γδ T cell high", but homologous SRCR molecules were maintained by all mammals.

Local immune response against larvae of Rhipicephalus (Boophilus) microplus in Bos taurus indicus and Bos taurus taurus cattle

Bos taurus indicus cattle are less susceptible to infestation with Rhipicephalus (Boophilus) microplus than Bos taurus taurus cattle but the immunological basis of this difference is not understood. We compared the dynamics of leukocyte infiltrations (T cell subsets, B cells, major histocompatibility complex (MHC) class II-expressing cells, granulocytes) in the skin near the mouthparts of larvae of R. microplus in B. t. indicus and B. t. taurus cattle. Previously naïve cattle were infested with 50,000 larvae (B. t. indicus) or 10,000 larvae (B. t. taurus) weekly for 6 weeks. One week after the last infestation all of the animals were infested with 20,000 larvae of R. microplus. Skin punch biopsies were taken from all animals on the day before the primary infestation and from sites of larval attachment on the day after the first, second, fourth and final infestations. Infiltrations with CD3(+), CD4(+), CD8(+) and gammadelta T cells followed the same pattern in both breeds, showing relatively little change during the first four weekly infestations, followed by substantial increases at 7 weeks post-primary infestation. There was a tendency for more of all cell types except granulocytes to be observed in the skin of B. t. indicus cattle but the differences between the two breeds were consistently significant only for gammadelta T cells. Granulocyte infiltrations increased more rapidly from the day after infestation and were higher in B. t. taurus cattle than in B. t. indicus. Granulocytes and MHC class II-expressing cells infiltrated the areas closest to the mouthparts of larvae. A large volume of granulocyte antigens was seen in the gut of attached, feeding larvae.

Murine J774 macrophages recognize LPS/IFN-g, non-CpG DNA or two-CpG DNA-containing sequences as immunologically distinct

Specific bacterial lipopolysaccharides (LPS), IFN-gamma, and unmethylated cytosine or guanosine-phosphorothioate containing DNAs (CpG) activate host immunity, influencing infectious responses. Macrophages detect, inactivate and destroy infectious particles, and synthetic CpG sequences invoke similar responses of the innate immune system. Previously, murine macrophage J774 cells treated with CpG induced the expression of nitric oxide synthase 2 (NOS2) and cyclo-oxygenase 2 (COX2) mRNA and protein. In this study murine J774 macrophages were exposed to vehicle, interferon gamma+lipopolysaccharide (IFN-g/LPS), non-CpG (SAK1), or two-CpG sequence-containing DNA (SAK2) for 0-18h and gene expression changes measured. A large number of immunostimulatory and inflammatory changes were observed. SAK2 was a stronger activator of TNFalpha- and chemokine expression-related changes than LPS/IFN-g. Up regulation included tumor necrosis factor receptor superfamily genes (TNFRSF's), IL-1 receptor signaling via stress-activated protein kinase (SAPK), NF-kappaB activation, hemopoietic maturation factors and sonic hedgehog/wingless integration site (SHH/Wnt) pathway genes. Genes of the TGF-beta pathway were down regulated. In contrast, LPS/IFN-g-treated cells showed increased levels for TGF-beta signaling genes, which may be linked to the observed up regulation of numerous collagens and down regulation of Wnt pathway genes. SAK1 produced distinct changes from LPS/IFN-g or SAK2. Therefore, J774 macrophages recognize LPS/IFN-g, non-CpG DNA or two-CpG DNA-containing sequences as immunologically distinct.

Polysaccharides derived from Yamoa (Funtumia elastica) prime gammadelta T cells in vitro and enhance innate immune responses in vivo

Yamoa (ground bark of Funtumia elastica tree) is marketed and sold as a dietary supplement with anecdotal therapeutic effects in the treatment of asthma and hay fever. We determined that Yamoa and Yamoa-derived polysaccharides affected innate immunity, in part, by priming gammadelta T cells. Gene expression patterns in purified bovine gammadelta T cells and monocytes induced by Yamoa were similar to those induced by ultrapure lipopolysaccharide (uLPS). In the presence of accessory cells, Yamoa had priming effects that were similar to those of LPS on bovine and murine gammadelta T cells, but much more potent than LPS on human gammadelta T cells. The bioactive component of Yamoa was delineated to a complex polysaccharide fraction (Yam-I). Intraperitoneal injection of Yamoa and Yam-I in mice induced rapid increases in peritoneal neutrophils directed by changes in chemokine expression. In support of a unique agonist found in Yam-I, similar peritonitis responses were also observed in TLR4- and MyD88-deficient mice. Therapeutic treatment with Yam-I resulted in decreased bacterial counts in feces from mice with Salmonella enterica serotype typhimurium (ST)-induced enterocolitis. This characterization of the immune stimulatory properties of polysaccharides derived from Yamoa suggests mechanisms for the anecdotal positive effects of its ingestion and that these polysaccharides show potential for application in innate protection from disease.

Profiling of the early transcriptional response of murine gammadelta T cells following TCR stimulation

Gammadelta T cells represent one of the three lineages of lymphocytes, along with alphabeta T cells and B cells, which express antigen receptors. Since their discovery over two decades ago, considerable effort has been made to understand their antigen specificity and their contribution to the immune response. From these studies, we have learned that gammadelta T cells recognize a different set of antigens than alphabeta T cells, acquire effector functions faster than alphabeta T cells, regulate the response of other immune cells during infection, and play distinct roles in immunity. The molecular basis for how gammadelta T cells manifest their unique functions, however, remains unknown. To address this, we profiled the genes upregulated soon after TCR stimulation in order to identify which gene networks associated with T cell effector function are induced in gammadelta T cells. Interestingly, most of the genes in this transcriptional profile were not unique to activated gammadelta T cells, as they were also expressed in activated alphabeta T cells. However, many of the genes within this profile were upregulated with faster kinetics and/or greater magnitude in activated gammadelta T cells than in activated alphabeta T cells. In addition, we found that the genes in the transcriptional profile of activated wild-type gammadelta T cells can be used as a standard to screen activated gammadelta T cells from mice with potential signaling defects for alterations in gammadelta TCR signal transduction. Thus, by defining the early transcriptional response of activated wild-type gammadelta T cells and by comparing their transcriptional profile to that of activated wild-type alphabeta T cells as well as to that of activated gammadelta T cells from signaling defective mice, we are able to gain important insights into the molecular basis for gammadelta T cell function.

Galectin-8 induces apoptosis in Jurkat T cells by phosphatidic acid-mediated ERK1/2 activation supported by protein kinase A down-regulation

Galectins have been implicated in T cell homeostasis playing complementary pro-apoptotic roles. Here we show that galectin-8 (Gal-8) is a potent pro-apoptotic agent in Jurkat T cells inducing a complex phospholipase D/phosphatidic acid signaling pathway that has not been reported for any galectin before. Gal-8 increases phosphatidic signaling, which enhances the activity of both ERK1/2 and type 4 phosphodiesterases (PDE4), with a subsequent decrease in basal protein kinase A activity. Strikingly, rolipram inhibition of PDE4 decreases ERK1/2 activity. Thus Gal-8-induced PDE4 activation releases a negative influence of cAMP/protein kinase A on ERK1/2. The resulting strong ERK1/2 activation leads to expression of the death factor Fas ligand and caspase-mediated apoptosis. Several conditions that decrease ERK1/2 activity also decrease apoptosis, such as anti-Fas ligand blocking antibodies. In addition, experiments with freshly isolated human peripheral blood mononuclear cells, previously stimulated with anti-CD3 and anti-CD28, show that Gal-8 is pro-apoptotic on activated T cells, most likely on a subpopulation of them. Anti-Gal-8 autoantibodies from patients with systemic lupus erythematosus block the apoptotic effect of Gal-8. These results implicate Gal-8 as a novel T cell suppressive factor, which can be counterbalanced by function-blocking autoantibodies in autoimmunity.

Expanded nonhuman primate tregs exhibit a unique gene expression signature and potently downregulate alloimmune responses

We have established two complementary strategies for purifying naturally occurring regulatory T cells (Tregs) from rhesus macaques in quantities that would be sufficient for use as an in vivo cellular therapeutic. The first strategy identified Tregs based on their being CD4+/CD25(bright). The second incorporated CD127, and purified Tregs based on their expression of CD4 and CD25 and their low expression of CD127. Using these purification strategies, we were able to purify as many as 1x10(6) Tregs from 120 cc of peripheral blood. Cultures of these cells with anti-CD3, anti-CD28 and IL-2 over 21 days yielded as much as a 450-fold expansion, ultimately producing as many as 4.7x10(8) Tregs. Expanded Treg cultures potently inhibited alloimmune proliferation as measured by a carboxyfluorescein succinimidyl ester- mixed lymphocyte reaction (CFSE-MLR) assay even at a 1:100 ratio with responder T cells. Furthermore, both responder-specific and third-party Tregs downregulated alloproliferation similarly. Both freshly isolated and cultured Tregs had gene expression signatures distinguishable from concurrently isolated bulk CD4+ T-cell populations, as measured by singleplex reverse transcriptase-polymerase chain reaction (RT-PCR) and gene array. Moreover, an overlapping yet distinct gene expression signature seen in freshly isolated compared to expanded Tregs identifies a subset of Treg genes likely to be functionally significant.

Antigen-independent priming: a transitional response of bovine γδ T-cells to infection

Analysis of global gene expression in immune cells has provided unique insights into immune system function and response to infection. Recently, we applied microarray and serial analysis of gene expression (SAGE) techniques to the study of γδ T-cell function in humans and cattle. The intent of this review is to summarize the knowledge gained since our original comprehensive studies of bovine γδ T-cell subsets. More recently, we have characterized the effects of mucosal infection or treatment with microbial products or mitogens on gene expression patterns in sorted γδ and αβ T-cells. These studies provided new insights into the function of bovine γδ T-cells and led to a model in which response to pathogen-associated molecular patterns (PAMPs) induces ‘priming’ of γδ T-cells, resulting in more robust responses to downstream cytokine and/or antigen signals. PAMP primed γδ T-cells are defined by up-regulation of a select number of cytokines, including MIP1α and MIP1β, and by antigens such as surface IL2 receptor α (IL-2Rα) and CD69, in the absence of a prototypic marker for an activated γδ T-cell, IFN-γ. Furthermore, PAMP primed γδ T-cells are more capable of proliferation in response to IL-2 or IL-15 in the absence of antigen. PAMPs such as endotoxin, peptidoglycan and β-glucan are effective γδ T-cell priming agents, but the most potent antigen-independent priming agonists defined to date are condensed oligomeric tannins produced by some plants.

Differential regulation of CD11b on gammadelta T cells and monocytes in response to unripe apple polyphenols

Leukocyte adhesion and migration are mediated partially by CD11b/CD18 (membrane-activated complex-1, CR3). Earlier studies have demonstrated a role for green tea polyphenols in down-regulating CD11b on CD8(+) T cells and monocytes. We have shown recently a stimulatory effect of unripe apple polyphenols (APP) on gammadelta T cells. Thus, we compared the effect of APP on bovine gammadelta T cell and monocyte CD11b expression. Purified bovine monocytes and monocyte-depleted PBLs were cultured with APP. CD11b levels decreased on monocytes in response to APP. In contrast, a gammadelta T cell subset responded to APP by up-regulating CD11b. The CD11b regulation was not seen on gammadelta T cells or monocytes treated with APP fractions depleted of tannins. The APP-induced down-regulation of CD11b on monocytes was inhibited by an anti-CD11b mAb, consistent with previous studies showing that polyphenols bind CD11b. As expected, the anti-CD11b mAb had no effect on the APP response in resting gammadelta T cells, as these cells lacked CD11b. Consistent with the changes in surface CD11b expression, APP-treated gammadelta T cells showed increased adherence to plastic, whereas monocyte adhesion was reduced. APP also induced cytokine gene expression in gammadelta T cells. Some polyphenols are thought of as anti-inflammatory agents; however, these data, as well as other ongoing studies, indicate they have a proinflammatory effect on gammadelta T cells. In vivo, plant polyphenols may enhance gammadelta T cell migration and function at sites of inflammation, where they could induce rapid, immune-regulatory and innate-like immune responses.