Molecular cloning, expression and characterization of ovine TNF alpha

Comparison of the human and canine cytokines IL-1(alpha/beta) and TNF-alpha to orthologous other mammalians

The cytokines interleukin-1 (IL-1alpha and IL-1beta) and the tumor necrosis factor-alpha (TNF-alpha) both play a major role in the initiation and regulation of inflammation and immunity responses. Polymorphisms within the gene sequences of these cytokines IL-1 and TNF-alpha have been proposed to play an important role in the pathogenesis of certain diseases. Affecting nearly every organ, various diseases, including some cancers, are described to be associated with an increased level of IL-1 and TNF-alpha proteins, for example, solid tumors, hematologic malignancies, malignant histiocytosis, autoimmune disorders, Alzheimer's disease, Parkinson's disease, sepsis, and rheumatoid arthritis. Regarding genetic backgrounds and pathways, numerous canine diseases show close similarities to their human counterparts. As a genetic model, the dog could be used to unravel the genetic mechanisms, for example, in particular the predispositions, the development, and progression of cancer and metabolic diseases. The identity comparison of gene and protein sequences of different species could be used to elucidate the structure and function of the genes and proteins by identifying the evolutionary conserved regions and domains. Herein we analyzed in detail the mRNA and protein structures and identities of the present known mammalian (human, canine, murine, rat, ovine, equine, feline, porcine, and bovine) TNF-alpha, IL-1alpha, and IL-1beta mRNAs and proteins. Additionally, based on the canine genome sequence, we derived in silico the complete mRNA structures of the IL-1alpha and IL-1beta mRNAs.

Alpaca (Lama pacos) as a convenient source of recombinant camelid heavy chain antibodies (VHHs)

Recombinant single domain antibody fragments (VHHs) that derive from the unusual camelid heavy chain only IgG class (HCAbs) have many favourable properties compared with single-chain antibodies prepared from conventional IgG. As a result, VHHs have become widely used as binding reagents and are beginning to show potential as therapeutic agents. To date, the source of VHH genetic material has been camels and llamas despite their large size and limited availability. Here we demonstrate that the smaller, more tractable and widely available alpaca is an excellent source of VHH coding DNA. Alpaca sera IgG consists of about 50% HCAbs, mostly of the short-hinge variety. Sequencing of DNA encoding more than 50 random VHH and hinge domains permitted the design of PCR primers that will amplify virtually all alpaca VHH coding DNAs for phage display library construction. Alpacas were immunized with ovine tumour necrosis factor alpha (TNFalpha) and a VHH phage display library was prepared from a lymph node that drains the sites of immunizations and successfully employed in the isolation of VHHs that bind and neutralize ovine TNFalpha.

Characterization of 37 Breed-Specific Single-Nucleotide Polymorphisms in Sheep

We identified 37 single-nucleotide polymorphisms (SNPs) in sheep and screened 16 individuals from 8 different sheep breeds selected throughout Europe. Population genetic measures based on the genotyping of about 30 sheep from the same 8 breeds are reported. To date, there are no sheep SNPs documented in the National Center for Biotechnology Information dbSNP database. Therefore, the markers presented here contribute significantly to those currently available.

Effects of implantation and early pregnancy on the expression of cytokines and vascular surface molecules in the sheep endometrium

Successful implantation is a highly coordinated process involving changes in cytokines, adhesion molecules, hormones, enzymes and growth factors. This study examines the expression of key cytokines and vascular surface molecules in the pregnant uterus of sheep around the time of implantation. Uterine tissues and uterine washings were collected from non-pregnant and pregnant sheep at 17-19 days post-coitus (dpc), 26-27 and 34-36 dpc. Reverse transcriptase-polymerase chain reaction (RT-PCR) analysis of caruncular/placentomal tissues revealed that cytokines IL-2, IL-4 and IL-8, which were not detected in non-pregnant uterus, were induced more strongly at 26-27 dpc than at other stages of pregnancy tested. Cytokines LIF, IL-6, IL-10, TNF-alpha were also most highly expressed at 26-27 dpc, expression of them being lower at other time-points during early pregnancy and non-pregnancy. The cytokines IL-1beta, IFN-gamma and TGF-beta were expressed in all non-pregnant and pregnant tissues examined. Enzyme-linked immunosorbent assay (ELISA) performed on uterine washings clearly detected the presence of IL-1alpha protein at 26-27 and 34-36 dpc. Immunohistochemistry revealed that expression of vascular adhesion molecule VCAM-1 in endometrial endothelium was strongly induced at 26-27 dpc in the pregnant endometrium. Expression of CD5 on vascular endothelium was not induced in placentomal tissues until 26-27 dpc and was further increased by 34-36 dpc. These results demonstrate a dynamic change in a wide range of cytokines during early stages of pregnancy, with a critical period around 26-27 dpc. In addition, at 26-27 dpc, expression of the surface/adhesion molecules, CD5 and VCAM-1, is induced on vascular endothelium of the sheep endometrium, possibly as a direct consequence of the changed cytokine environment, and may be involved in directing the changes in leucocyte migration observed during pregnancy.

Detection of polymorphisms in the tumour necrosis factor alpha candidate gene in sheep

Primers based on GenBank sequences of the ovine tumour necrosis factor (TNF)-alpha gene were designed to amplify a 273-bp fragment comprising part of the fourth exon and the 3' untranslated region (UTR) of the ovine TNF-alpha gene. Five different single-strand conformational polymorphism (SSCP) patterns were detected in a number of unrelated animals and three different alleles were identified and sequenced. These alleles differed in one deletion and one single nucleotide polymorphism (SNP) and were named TNF*01, TNF*02 and TNF*03. These alleles corresponded to three sequences previously characterized by other groups. In the population analysis, no significant differences were found in the frequencies of the Latxa and Rasa breeds. This is the first description of allelic variation in the ovine TNF-alpha gene.

Quantification of ovine cytokine gene expression by a competitive RT-PCR method

A quantitative competitive RT-PCR method was developed in order to measure IL-1beta, IL-4, IL-12, IFNgamma, TNFalpha and G(3)PDH mRNA from samples of ovine tissue such as lymph node or spleen. The main advantage of the method relies on the use, for each target sequence, of an internal competitor construct similar to the relevant target, but 4-bp different in size. This competitive strategy is validated by the equivalence of the amplification process, observed separately between competitor DNA and target DNA species. Furthermore, the copy number of each cytokine cDNA is normalized to a fixed copy number of G(3)PDH cDNA. The cDNA level of this constitutive gene was effectively shown to remain constant whatever the tissue studied and independently of the experimental conditions used. The accurate and reproducible data obtained permit the application of this quantitative RT-PCR method to measure the sheep cytokine response to Salmonella infection. Early induction of IFNgamma mRNA was observed in the draining lymph node 1 day after infection. At the same time, a strong increase of IL-1beta mRNA was observed in local and systemic lymphoid organs, suggesting the initiation of the inflammatory response. Finally, the overall results demonstrate the efficiency of the method and its suitability for further studies of the immune response in the ovine species.

Molecular cloning, characterization, and expression of TNF cDNA and gene from Japanese flounder Paralychthys olivaceus

We cloned a cDNA and the gene for Japanese flounder TNF. The TNF cDNA consisted of 1217 bp, which encoded 225 amino acid residues. The identities between Japanese flounder TNF and members of the mammalian TNF family were approximately 20-30%. The positions of cysteine residues that are important for disulfide bonds were conserved with respect to those in mammalian TNF-alpha. The Japanese flounder TNF gene has a length of approximately 2 kbp and consists of four exons and three introns. The positions of the exon-intron junction positions of Japanese flounder TNF gene are similar to those of human TNF-alpha. However, the length of the first intron of Japanese flounder is much shorter than that of the human TNF-alpha gene. There are simple CA or AT dinucleotide repeats in the 5'-upstream and 3'-downstream regions of the Japanese flounder TNF gene. Southern blot hybridization indicted that Japanese flounder TNF exists as a single copy. Expression of Japanese flounder TNF mRNA is greatly induced after stimulation of PBLs with LPS, Con A, or PMA. These results indicated that Japanese flounder TNF is more like mammalian TNF-alpha than mammalian lymphotoxin-alpha, with respect to its gene structure, length of amino acid sequence, number and position of cysteine residues, and regulation of gene expression.

Early immunopathological events in experimental ovine paratuberculosis

An experimental oral infection of neonatal (< 2 weeks old) lambs with a cervine isolate of Mycobacterium avium subspecies paratuberculosis (M.a. paratuberculosis), the causal agent of ruminant paratuberculosis (Johne's disease) was used to investigate bacteriological, histopathological and immunological changes during the early (up to 8 weeks) post-infection phase. In vitro culture for mycobacteria was positive in one faecal and three mesenteric lymph node (MLN) samples from the eight infected lambs. All mycobacterial isolates from MLN were identified as M.a. paratuberculosis by polymerase chain reaction (PCR). Small-to-medium sized focal granulomata were observed in jejunal (JPP) and ileal Peyer's patches (IPP) from four of the eight infected lambs. Compared with controls, JPP from all infected lambs had significantly (p < 0.05) higher proportions of CD8+ and CD2+ lymphocytes, and there were significantly (p < 0.05) fewer cells expressing B lymphocyte-associated markers in IPP and MLN. The T/B cell ratio was significantly (p < 0.05) increased in both JPP and MLN from infected lambs. The expression of a range of genes for cytokines was examined using specific reverse transcriptase PCR (RT-PCR) amplification of messenger RNA (mRNA) template isolated from MLN, JPP and IPP from both groups of animals. Densitometric analyses indicated that, in infected animals, MLN expressed significantly (p < 0.05) more mRNA for TNF-alpha: JPP had significantly increased (p < 0.05) mRNA for GM-CSF and significantly decreased (p < 0.05) mRNA for IL-4 and IFN-gamma. Infected lambs had significantly (p < 0.05) decreased titres of both circulating IgG and gut mycobacteria-associated IgG antibody. Infection was not associated with any consistent changes in lymphocyte reactivity to specific mycobacterial antigens, IFN-gamma release into supernatants from in vitro intestinal lymphocyte cultures or gut IgA antibody levels.

Differential synthesis, cellular localisation and secretion of interleukin-1 alpha interleukin-1 beta from ovine macrophages

In order to characterise the regulatory processes involved in expression of ruminant interleukin 1 (IL-1) biological activity, we have used specific monoclonal antibodies to assess synthesis, cellular localisation and secretion of ovine IL-1 alpha and IL-1 beta from alveolar macrophages. Immunoprecipitation of IL-1 alpha and IL-1 beta from lysates of macrophages cultured in media alone or media supplemented with lipopolysaccharide (LPS) revealed that both forms of IL-1 were synthesised as precursor proteins of 31-33 kDa. In contrast, both IL-1 species were immunoprecipitated from culture supernatants as 17 kDa molecules. Comparison of the precipitated bands from culture supernatants suggested that significantly more IL-1 beta than IL-1 alpha was secreted by the macrophages. Flow cytometric analysis of IL-1 alpha and IL-1 beta expression by fresh unstimulated macrophages and macrophages cultured for 5 h with LPS demonstrated that a proportion of the cell associated IL-1 alpha, but not IL-1 beta, in stimulated macrophages was expressed at the cell surface. Analysis of IL-1 secretion by cultured alveolar macrophages, using IL-1 alpha and IL-1 beta specific immunoassays, confirmed that IL-1 beta was the predominant secreted species of IL-1. While cell associated IL-1 alpha and IL-1 beta were detected by immunoprecipitation and flow cytometric analysis of macrophages cultured in media alone or media supplemented with LPS, secreted IL-1 beta was detected only after stimulation of macrophages with LPS. This indicates a dissociation of IL-1 beta synthesis and secretion and is indicative of an IL-1 beta converting enzyme similar to that which has been described in the human and mouse models.

Inflammatory cytokines in animal health and disease

Inflammatory cytokines, including tumor necrosis factor (TNF), interleukin-1 (IL-1), IL-6 and IL-8, are rapidly induced early in a disease or injury process. They mediate and modulate myriad healing processes but, if overexpressed, may exacerbate the severity of a disease condition. In order to test this concept and to establish a foundation for the role of inflammatory cytokines in the pathogenesis of gram-negative bacterial infections in the respiratory tract of animals, the patterns of inflammatory cytokine expression were determined in experimental porcine pleuropneumonia. We observed that IL-1 and IL-6, but not TNF, were rapidly and dramatically elevated in the lavage fluid of the lung within 24 h of infection. The increased levels of IL-1 might contribute to increased severity of disease, but elevated IL-6 levels were consistent with a protective acute phase response. Additional studies were performed to examine the hypothesis that IL-4 expression later in infection might be involved in turning off the inflammatory response and promoting an antigen-specific humoral immune response. Interleukin-4 efficiently suppressed inflammatory cytokine production in alveolar macrophages. Its expression was induced in peripheral blood mononuclear cells by TNF, IL-4, and by reexposure to a specific antigen. To obtain the maximum amount of information on the role of inflammatory cytokines in animals of veterinary significance it will be useful to perform studies in species such that evolutionary relatedness will allow widespread application of the findings. Furthermore, the variety of molecules involved in inflammatory cytokine regulation will require much more extensive investigations of the relevant enzymes, inhibitors and receptors in veterinary species. Finally, the complexity and redundancy of immune defenses in animals mean that attempts to modulate health status through manipulation of inflammatory cytokines must be performed with caution and that a multiplicity of processes will be affected.

IgE, TNF alpha, IL1 beta, IL4 and IFN gamma gene polymorphisms in sheep selected for resistance to fleece rot and flystrike

Investigation of restriction fragment length polymorphisms (RFLPs) associated with immunoglobulin E (IgE) and cytokine genes in the sheep genome revealed polymorphisms in the IgE constant heavy chain, interferon gamma and interleukin 4 genes. No polymorphisms were found in interleukin 1 beta or tumour necrosis factor alpha. PstI and BamHI RFLPs in the IgE gene showed differences in frequency between animals selected for resistance or susceptibility to fleece rot and blowfly strike.

Molecular cloning and characterization of tumor necrosis factor alpha (TNF-alpha) from the Australian common brushtail possum, Trichosurus vulpecula

Immune responses in the Australian common brushtail possum (Trichosurus vulpecula) and in particular the role of cytokines are poorly understood. We have undertaken to isolate cytokine genes using reverse transcriptase-polymerase chain reaction (RT-PCR) and in this study describe the molecular cloning of TNF-alpha. Primers were designed from consensus sequences at the N-terminus end of eutherian mammalian TNF-alpha and the possum cDNA, derived from spleen RNA, identified by RT-PCR. The complete cDNA encoding possum TNF-alpha was amplified from lymphocyte RNA by 5' and 3' rapid amplification of cDNA ends (RACE). The nucleotide sequence of the protein coding region of this cDNA shared 66-69% identity with other mammalian TNF-alpha genes. The predicted protein of 233 amino acids shared 56-58% identity with eutherian mammalian TNF-alpha was expressed in both Saccharomyces cerevisiae and Escherichia coli by constructing expression plasmid derivatives of the vectors pYES2 and pGEX-2T respectively. Cell extracts prepared from transformants and the purified GST/TNF-alpha fusion protein exhibited cytotoxic activity on the TNF-alpha-sensitive murine fibroblast L929 cells and stimulated proliferation of possum thymocyte cells. The induction of possum TNF-alpha mRNA in alveolar macrophages was analysed by RT-PCR using possum-specific TNF-alpha primers. Macrophages cultured in the presence of LPS showed enhanced transcription of TNF-alpha mRNA. This is the first report of the cloning and sequence analysis of the cDNA encoding a marsupial cytokine gene.

Macrophage function in deer

Macrophage inflammatory and immune functions were characterised in red deer (cervus elaphus), for use as a model for natural infection with bovine tuberculosis. Highly enriched populations of deer macrophages were obtained from 14 day cultures of plastic-adherent peripheral blood mononuclear cells. Cervine macrophages produced superoxide anion in response to respiratory burst stimuli (serum-opsonised zymosan and phorbol myristic acetate), but nitric oxide production could not be detected under the conditions tested. The lysosomal enzymes acid phosphatase and lysozyme were detected at the intercellular and extracellular level. Stimulation with bacterial lipopolysaccharide extract (Escherichia coli LPS) enhanced the production of superoxide and acid phosphatase with a peak increase in activity observed after 2h. Production of interleukin 1 (IL-1) and tumour necrosis factor (TNF), determined using cytokine-sensitive cell lines and mRNA analysis (Northern blotting), indicated maximal secretion of both cytokines after 24 h stimulation with LPS, preceded by a peak in message accumulation at 2-6 h post-stimulation. Cervine macrophages stimulated proliferative responses in T cell-enriched lymphocyte populations derived from the peripheral blood of autologous animals that had been primed to mycobacterial antigens (Mycobacterium bovis Bacille Calmette-Guerin, BCG). Macrophages were able to stimulate responses after pulsing with particulate (BCG) or soluble (purified protein derivative) mycobacterial antigens. These results indicate that macrophage inflammatory and immune responses in red deer are similar to those in other mammalian species, and that macrophages may play an important role in resistance to mycobacterial infection.

Expression, biological activity and kinetics of production of recombinant ovine TNF-alpha

Ovine tumour necrosis factor-alpha (OvTNF-alpha) was cloned by reverse transcription-polymerase reaction using RNA isolated from lipopolysaccharide (LPS)-stimulated alveolar macrophages and primers based on the human TNF-alpha cDNA sequence. An expression vector carrying the coding sequence of the mature form of ovine TNF was constructed. The recombinant Ov-TNF alpha (rOvTNF-alpha) was expressed as a glutathione-S-transferase (GST) fusion protein. It was cleaved with thrombin to yield rOvTNF free of the GST moiety. Growth at a lower temperature of 30 degrees C and use of Escherichia coli strains AM207, AM305, E392 and NM522 did not improve the recovery of rOvTNF-alpha from the soluble fraction to a significant extent. Purification of recombinant proteins was achieved rapidly and easily by affinity chromatography using glutathione-Sepharose. Yields of pure rOvTNF-alpha achieved in E. coli JM109 and AM207 were approximately 1 mg L-1. Both rOvTNF-alpha and recombinant human TNF-alpha (rhTNF-alpha) exerted cytotoxicity on L929 cells. However, rOvTNF-alpha but not rhTNF-alpha stimulated proliferation of ovine thymocytes. Maximum levels of TNF-alpha mRNA expression by LPS-stimulated ovine alveolar macrophages were detected at approximately 4 h post-stimulation.

Cytokine mRNA expression in skin in response to ectoparasite infection

Cellular infiltration and local cytokine mRNA levels were examined during the first 48 h of infection of skin by larvae of the sheep blowfly Lucilia cuprina. At the cellular level the response involved a dramatic influx of leucocytes (CD45+ cells). Among these infiltrating cells were large numbers of granulocytes, including neutrophils and eosinophils, as well as macrophage-like cells and lymphocytes. Many of the lymphocytes expressed cell surface markers characteristic of T cells including CD4, CD8 and the gamma delta TCR. The numbers of each of these cell types increased progressively as infection continued so that by 48 h the lesions were densely populated. Expression of mRNA for IL-6 could be detected by Northern blot analysis while mRNA for other inflammatory cytokines including IL-1 alpha, IL-1 beta, IL-8 and TNF alpha was detected using the polymerase chain reaction. Coincident with the influx of granulocytes and other cells there was an increase in the level of mRNA for the cytokines IL-1 alpha, IL-1 beta, IL-6 and IL-8. In the skin of the sheep there appeared to be constitutive expression of message for the cytokines IL-1 beta, IL-6 and TNF alpha, with the level of the latter not found to increase during the 48 h of infection examined. In situ hybridization was used to determine the location of IL-6 and TNF alpha mRNA within resting and infected skin. During infection, fibroblasts, macrophage-like cells and endothelium appeared to produce high levels of IL-6 mRNA. Expression of the T cell dependent cytokines IL-2 and IFN-gamma but not IL-4, increased in expression as time progressed and the population of infiltrating cells, including T cells, expanded.

Characterization of monoclonal antibodies to ovine tumor necrosis factor-alpha and development of a sensitive immunoassay

Monoclonal antibodies (mAbs) and a polyclonal rabbit antiserum were raised against recombinant ovine tumor necrosis factor-alpha (rovTNF alpha). Ten mAbs specific for rovTNF alpha were isolated and designated TNF1-10. All mAbs were of the IgG1 isotype and reacted with rovTNF alpha in Western blot analysis. Eight of the ten mAbs, TNF1, TNF3-7 and TNF9 and 10, completely blocked the activity of rovTNF alpha and macrophage derived native ovTNF alpha, as measured by their ability to inhibit TNF alpha-mediated lysis of WEHI-164 or L929 cells. In addition, TNF3, -7, -9 and -10 blocked the cytolytic activity of recombinant human TNF alpha (rhuTNF alpha). However, when tested for the ability to inhibit TNF alpha induced thymocyte proliferation, only mAbs TNF1, -3, -5, -7, -9 and -10 could completely block activity. Competitive binding analysis using unlabelled and horseradish peroxidase (HRPO) labelled mAbs indicated that the mAbs could be divided into five groups based on their reactivity with rovTNF alpha. The mAbs were used to develop a sensitive sandwich immunoassay for the detection of ovTNF alpha. All combinations of mAbs and the polyclonal antiserum were tested to determine which pair of antibodies gave the most sensitive assay. The combination of TNF5 as the capture antibody and the polyclonal antiserum gave the most sensitive result, detecting less than 0.24 ng rovTNF alpha ml-1. A similar sensitivity was obtained when TNF4 was used as the capture antibody and TNF10 HRPO labelled mAb as the second antibody. The immunoassay was more sensitive than the WEHI-164 bioassay which had a detection limit of 1 ng ml-1 for rovTNF alpha. This immunoassay also detected glycosylated ovTNF alpha in the supernatant of COS-7 cells which had been transfected with an ovTNF alpha cDNA.

Recombinant cytokines as immunological adjuvants

This paper describes the bacterial expression and purification of bioactive recombinant ovine interleukin-2 (rovIL-2), interleukin-1 alpha (rovIL-1 alpha) and tumour necrosis factor alpha. These purified proteins had specific activities in appropriate bioassays of 1 x 10(7) 1 x 10(7) and 1 x 10(5) U/mg, respectively. Recombinant ovIL-1 alpha was assessed as an immunological adjuvant for the sheep response to the model protein avidin. When delivered either intradermally or intramuscularly in conjunction with avidin in aluminium hydroxide the rovIL-1 alpha significantly enhanced the secondary humoral response. Doses of 1, 10 or 100 micrograms per sheep enhanced the humoral response to a similar extent. Recombinant ovIL-1 beta had similar adjuvant activity in that it was demonstrated to significantly enhance the sheep humoral response to an experimental H. contortus antigen. This increase in specific antibody, however, did not correlate with enhanced protection against infection with third stage H. contortus larvae. In addition incorporation of rovIL-1 beta into the formulation was shown not to alter the isotype profile of H. contortus antigen specific antibody.

Current research on ovine cytokines

Cytokines are key mediators of the immune system, dictating the quality of the host response to infection. The importance of such immune mediators to the development of immune and inflammatory responses has emerged from work in mouse and man, however it has now become necessary to produce the equivalent (and novel) cytokines in ruminants. Over the past three years recombinant DNA techniques have allowed the cloning of numerous ovine cytokines. These include interleukins -1, -2 and -3 (IL-1, -2 and -3), interferon-gamma (IFN-gamma), ovine trophoblast protein (oTP-1), tumour necrosis factor-alpha (TNF-alpha) and granulocyte-macrophage colony-stimulating factor (GM-CSF). The predicted amino-acid sequences of these ovine proteins show varying degrees of similarity with the equivalent human proteins thus explaining why some of the cytokines are not biologically cross-reactive between species. Recombinant ovine proteins have been produced for IFN-gamma, oTP-1, IL-1, IL-3 and GM-CSF. Their biological activities are very similar to those of their human counterparts. Although it is too early to tell whether the recombinant ovine proteins will be of use in the treatment or prophylaxis of infectious disease, work in cattle and pigs has indicated the potential usefulness of cytokines in this role.

Expression and characterization of bioactive recombinant ovine TNF-alpha: some species specificity in cytotoxic response to TNF

We have expressed and partially purified recombinant ovine tumour necrosis factor alpha (rovTNF-alpha) using a yeast Ty, virus like particle, expression system. RovTNF-alpha is at least as active as recombinant human TNF-alpha (rhTNF-alpha) in two different bio-assays performed on ovine material, whilst approximately 1000-fold more rovrTNF-alpha than rhTNF-alpha is required to induce the same level of cytotoxicity in TNF-sensitive murine cell lines L929 and WEHI 164 clone 13. When cytotoxic assays are performed on the porcine TNF sensitive cell line PK(15)-1512, rovTNF-alpha shows about 2 logs greater activity than on murine cells, whilst rhTNF-alpha is about 1 log more active. A monoclonal antibody, raised against rovTNF-alpha, has been used to demonstrate the presence of nanogram amounts of an appropriately sized glycoprotein to be native ovine TNF-alpha in supernants of LPS stimulated ovine alveolar macrophages. These samples show no detectable cytotoxicity to L929 cells, although they show activity attributable to TNF-alpha (through neutralization by a polyclonal antiserum raised to rovTNF-alpha) in an assay on ovine material. The relative lack of activity on murine cells helps to explain previous reports of inability to assay native ovine TNF-alpha using these cells, in spite of their routine use to assay TNF-alpha from several other species. The sequence features in ovine TNF-alpha which might reduce its affinity for the murine TNF type 1 receptor are discussed.