Inflammation-induced changes in the phenotype and cytokine profile of cells migrating through skin and afferent lymph

In the present study, we have localized cytokine-secreting cells within an ectoparasite-induced inflammatory lesion and monitored the phenotype and cytokine profile of cells migrating from the inflammatory lesion to the local draining lymph node via the afferent lymphatics. Interleukin (IL)-8-producing cells were first detected in skin within 6 hr of infection, with increased numbers observed at 24 and 48 hr post infection. While these cells were concentrated within the neutrophil influx, adjacent to disrupted epidermis; they were also found scattered throughout the surrounding dermis in areas where significant cellular infiltration was not apparent. IL-1 alpha- and IL-1 beta-producing cells could not be detected until 24 hr after infection and were restricted to areas of intense neutrophil accumulation. Concurrent with the onset of inflammation was a threefold increase in the total number of cells migrating through the draining afferent lymph. This increase in cellularity was due primarily to increased migration of CD4 and gamma delta T cells. Cytokine mRNA synthesis by migrating afferent lymph cells was examined by reverse transcription-polymerase chain reaction (RT-PCR) analysis of RNA extracted prior to, and at regular intervals during the course of the inflammatory response. IL-1 beta and IL-8, but not IL-1 alpha or IL-6 mRNA, was detected in migrating afferent lymph cells. Tumour necrosis factor (TNF)-alpha-specific mRNA was present in migrating afferent lymph cells at all time points both prior to, and following infection. Soluble IL-8 protein, but not IL-1 alpha, IL-1 beta or TNF-alpha protein, could be detected in lymph, with the amount of IL-8 detected increasing as the infection progressed. mRNA coding for cytokines associated with T-cell activation, such as IL-2, IL-4 or interferon (IFN)-gamma, was also detected in migrating cells, although the cytokine profiles of different experimental animals were extremely variable.

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.

Local cell traffic and cytokine production associated with ectoparasite infection

This paper reviews recent advances in our understanding of changes in local cellular traffic and cytokine synthesis that occur as a result of infection of sheep with the ectoparasite Lucilia cuprina. Changes in the cellular composition and cytokine profile of infected skin and draining afferent and efferent lymph were assessed using standard approaches and, in addition, a variety of techniques that have only recently become available as a result of advances in ruminant cytokine biology. These include cytokine-specific immunoassay, reverse transcription PCR (RT-PCR) and immunohistology. The initial acute inflammatory response was characterised by the infiltration of polymorphonuclear cells followed by selected lymphocyte subsets into discrete areas adjacent to the site of infection. Analysis of cytokine expression in skin prior to and following infection provided a molecular basis for the observed cellular events. Both cellular and molecular events within the skin were reflected within draining afferent lymph providing a basis for the conclusion that events within the skin (other than antigen uptake and transport) may influence events within the draining node and thus the outcome of the immune response to the parasite. Analysis of cellular and molecular changes in efferent lymph during infection suggested initiation of antigen-specific immunity.

Follistatin concentrations in male sheep increase following sham castration/castration or injection of interleukin-1 beta

Plasma follistatin (FS) concentrations were determined after castration (n = 5) or sham castration (n = 4) of mature rams. Both treatments resulted in a prolonged increase in FS between 7 and 19 h after surgery, which returned to pretreatment concentrations by 24 h. Tumour necrosis factor-alpha (TNF-alpha), a sensitive maker of an acute-phase response, was undetectable in plasma, indicating that the FS response was not induced by trauma due to surgery. In a second experiment, injection of castrated rams (n = 4) with ovine recombinant interleukin-1 beta, an acute-phase mediator, resulted in a sustained rise in FS concentrations within 4 h of injection. Plasma TNF-alpha concentrations increased transiently within 1 h of interleukin-1 beta injection, indicating that an acute-phase response had been initiated. Plasma follicle-stimulating hormone (FSH) concentrations were significantly decreased at 8 and 24 h after interleukin-1 beta injection, strongly suggestive of an inhibitory effect of increased FS concentrations on the secretion of FSH. Injection of castrated rams (n = 2) with a control preparation of recombinant interleukin-2 did not induce an acute-phase response, and plasma FS and FSH concentrations were unaffected. These data show that the testis is not a major source of circulating FS, that the increase in circulating FS following sham castration/castration is not due to an acute-phase response, but that conversely FS concentrations are modulated by the acute-phase mediator, interleukin-1 beta.

Vaccination of sheep against larvae of the sheep blowfly (Lucilia cuprina)

Four first stage larval antigens from the sheep blowfly were identified using supernatants from cultures of antibody secreting cells. These partially purified larval antigens, when added to Montanide ISA-25 containing recombinant ovine IL-1 beta (rovIL-1 beta) were used to successfully vaccinate sheep against larvae of the sheep blowfly. Significantly less strikes were recorded on vaccinated sheep compared to controls (P < 0.033) with surviving larvae from vaccinated sheep up to 85% smaller than larvae from control sheep. RovIL-1 beta was found to be an important component of the vaccine. Vaccinated sheep showed both humoral and cellular immune responses to the larval antigens. Antibody levels generally correlated directly with delayed-type hypersensitivity (DTH) responses, but neither antibody nor DTH correlated positively with protection in vaccinated sheep. Skin sections removed from individual sheep immediately after challenge revealed aggregations of CD4+, gamma delta-TCR+ and CD1+ cells located directly under the epidermis in vaccinated sheep.

Cytokines as adjuvants for ruminant vaccines

Successful vaccination against any potential pathogen is critically dependent on inducing an appropriate immune response. The pivotal role of cytokines in the immune response to vaccination suggests that non-protective responses or responses that exacerbate disease subsequent to infectious challenge may be the result of limiting or preferential production of one or a number of these mediators. This suggests that the use of recombinant cytokines as vaccine adjuvants may offer a mechanism whereby the magnitude and phenotype of the immune response to vaccination can be specifically modified. In mice, recombinant cytokines have been used extensively as therapeutics, while studies describing vaccine adjuvant activity are more limited. Recombinant (r) interleukin (IL)-1, IL-2 and interferon (IFN) gamma have been used primarily to enhance humoral responses with enhanced protection assessed where appropriate. Cytokine adjuvant studies in ruminants have been restricted to recombinant ovine (rov) and bovine (rbov) IL-1 and IL-2. In sheep, their application has been optimised with respect to dose, route of delivery and formulation, for induction of humoral and cell mediated immunity (DTH and cytotoxicity) to the model protein antigen (Ag) avidin. The level of adjuvant activity of IL-1 in particular compares favourably to that of a variety of other traditional and new chemical adjuvants and detailed analysis has indicated no adverse local or systemic side-effects. Recent studies in our laboratory demonstrating the effectiveness of rovIL-1 as an adjuvant in single and multi-component bacterial toxoid vaccines, and studies from other laboratories demonstrating the application of rbovIL-1 as an adjuvant for the response in cattle to live attenuated viral vaccines, suggest that rIL-1 may become the adjuvant of choice for diseases where protection is mediated by high levels of circulating antibody (Ab). With respect to helminth parasites, IL-1 may prove useful as a component of vaccines based on "hidden Ags" which rely on induction of Ab. Based on analysis in mouse models of helminth infection, other cytokines such as IL-4 and IL-10 may be appropriate for vaccines based on induction of mechanisms involved in natural immunity.

Parameters related to the application of recombinant ovine interleukin-1 beta as an adjuvant

This paper describes aspects of the safety and efficacy of recombinant ovine interleukin-1 beta (rovIL-1 beta) as an immunological adjuvant. A dose-response relationship was established using the intramuscular route, and significant adjuvant activity was observed following delivery of 10 or 100 micrograms of the cytokine delivered either in PBS or in combination with alum. Similar doses of rovIL-1 beta also showed adjuvant activity when delivered via the subcutaneous route. In experiments in both mice and sheep, rovIL-1 beta-mediated adjuvant activity was neutralised by a monoclonal antibody (mAb), 3.41, confirming that the adjuvant effect was due to the biological activity of the cytokine. Serum clearance rates and physiological responses to intravenous, intramuscular or subcutaneous administration of rovIL-1 beta in sheep were also determined. RovIL-1 beta was shown to have a serum half-life of 2 min. Transient body temperature increases of 2 degrees C following intravenous or subcutaneous delivery, or 1 degrees C following intramuscular delivery, were observed. White blood cell counts also fluctuated post-injection, which was shown to be due to changes in the number of circulating neutrophils. The action of the neutralising mAb on serum clearance, body temperatures and white cell counts was also determined. Co-injection of rovIL-1 beta with the mAb 3.41 prevented rapid clearance of the cytokine from the serum, and was associated with an extension in elevated body temperature. The mAb appeared to have no significant influence on the white blood cell profile induced following injection with rovIL-1 beta.

Humoral and cellular responses induced by intradermally administered cytokine and conventional adjuvants

Serum antibody responses to the model protein antigen avidin were monitored in sheep following intradermal injection of avidin formulated with a range of commercially available and experimental adjuvants, including muramyl dipeptide (MDP), aluminium hydroxide gel (alum), recombinant ovine interleukin1 beta (rovIL-1 beta), rovIL-1 beta + alum, Quil A + alum or Emulsigen Plus. The highest antibody responses were recorded for animals immunised with avidin in rovIL-1 beta + alum, Quil A + alum or Emulsigen Plus, with moderate responses resulting from use of rovIL-1 beta or alum alone as adjuvants. Lower antibody responses to avidin were recorded when avidin was administered alone or with MDP. Delayed-type hypersensitivity (DTH) responses to avidin indicated that the most pronounced cellular response occurred in animals immunised with rovIL-1 beta + alum. Local cellular changes induced after primary and secondary intradermal injections indicated that distinct patterns of cellular recruitment were induced by the different adjuvants. Avidin with MDP resulted in an elevation of CD4+ T cells in the upper dermis while Emulsigen Plus induced an infiltration of large numbers of neutrophils throughout the dermis and reticular layers. CD4+, CD8+ and gamma delta + T cells increased in number and were found evenly distributed throughout these regions. Alum-based adjuvants resulted in the development of distinct cellular accumulations comprising primarily CD4+ T cells and CD45R + B cells arranged in distinct foci in the reticular layer. These cells were strongly class II positive as were the majority of macrophage like cells surrounding the foci. Staining for factor VIII related antigen indicated the presence of endothelial venules in the T and B cell foci and surrounding tissues.

Cloning and characterisation of an ovine interleukin-10-encoding cDNA

Expression of the interleukin 10-encoding (IL-10) mRNA by ovine (ov-) cells, in response to mitogenic stimulation, was assessed by Northern blot and polymerase chain reaction (PCR) analyses using a human (hu) IL-10 cDNA probe and oligodeoxyribonucleotide primers based on homologous regions of the human and murine IL-10 cDNA sequences. A 315-bp cDNA generated by the PCR analysis was cloned and used to screen a lipopolysaccharide-stimulated alveolar ov-macrophage cDNA library. The full-length ov-cDNA sequence isolated translates to a protein of 177 amino acids (aa) with a predicted 18-aa leader sequence and molecular mass of 20,165 Da. Expression in a mammalian system demonstrated that the ov-cDNA encoded a protein with the expected IL-10 biological activity. Both recombinant huIL-10 and supernatants from COS cells transfected with an expression vector containing the ovIL-10 cDNA inhibited production of IL-1 and tumour necrosis factor-alpha by ov-alveolar macrophages. Genomic DNA analysis indicated ovIL-10 exists as a single gene within the ov-genome.

Cloning and expression of a cDNA encoding ovine interleukin 7

Using the polymerase chain reaction (PCR) and primers based on regions of homology between the human and murine interleukin 7 (IL-7)-encoding cDNAs, we have amplified an ovine (ov) IL-7 cDNA from reverse-transcribed RNA extracted from concanavalin A (Con A)-activated ovine lymph-node cells. The nucleotide sequence of the cDNA and the predicted amino acid (aa) sequence showed significant homology to those of the human and murine molecules. The ovIL-7 cDNA encodes a 176-aa polypeptide that, based on analysis of murine IL-7, is processed to a protein of 151 aa. The cDNA was demonstrated to encode a protein with IL-7 biological activity. Supernatants from COS or CHO-K1 cells transfected with an expression vector containing the ovIL-7 cDNA were able to synergise with a suboptimal level of Con A to induce proliferation of ovine thymocytes. In addition, both supernatants were able to induce thymocyte proliferation, albeit at a reduced level, in the absence of Con A. Further experiments demonstrated that for induction of ovine thymocyte proliferation, recombinant (re)-ovIL-7 was able to synergise with re-human (h) IL-2 but not re-hIL-6 or tumor necrosis factor-alpha (re-hTNF alpha).

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.

Development of a sandwich immunoassay for the detection of soluble ovine IL-2R alpha chain

Following T cell activation with antigen or mitogens, there is an up-regulation of interleukin-2 receptor alpha (IL-2R alpha) chain expression. A high proportion of the IL-2R alpha chain is shed from the surface of the T cell in a soluble form following proteolytic cleavage, and thus determination of soluble IL-2R alpha (sIL-2R alpha) chain is an excellent measure of lymphocyte activation. A sandwich immunoassay for the detection of ovine sIL-2R alpha chain has been developed. Three monoclonal antibodies (mAbs) with specificity for the IL-2R alpha chain, demonstrated by immunoprecipitation of a 50 kDa protein from an ovine IL-2R alpha chain cDNA transfected Chinese hamster ovarian (CHO IL-2R) cell line, were analysed for additive and competitive binding to CHO IL-2R cells and Concanavalin A (Con A) activated ovine lymphocytes, respectively. Two non-competitive ovine IL-2R alpha chain specific mAbs were then used in a sandwich immunoassay to detect native sIL-2R alpha chain in the supernatant (SN) of Con A activated ovine lymphocytes and recombinant sIL-2R alpha chain in the SN of CHO IL-2R cells. Soluble IL-2R alpha chain could also be detected in complex biological fluid. In the efferent lymph of a cannulated ovine popliteal lymph node (LN), an increase in the level of sIL-2R alpha chain following local alloantigen LN activation was observed. This increase correlated with an increase in the output of activated T cell blasts.

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.

Production and application of monoclonal antibodies to ovine interleukin-1 alpha and interleukin-1 beta

Monoclonal antibodies (mAbs) were raised against recombinant ovine interleukin-1 alpha and beta (ovIL-1 alpha and ovIL-1 beta). Five ovIL-1 alpha specific mAbs and three ovIL-1 beta specific mAbs, all of the IgG1 isotype, were characterized. Four of the five ovIL-1 alpha specific mAbs, designated 10.36, 10.49, 10.82 and 5.16, fell into two distinct groups based on several criteria. MAbs 10.36, 10.49 and 10.82 reacted with recombinant ovIL-1 alpha in Western blot analysis, were potent in neutralizing ovIL-1 alpha biological activity in vitro and bound to the same or a closely related epitope. MAb 5.16 also bound ovIL-1 alpha in Western blot analysis, but was less potent in neutralizing ovIL-1 alpha biological activity and bound to a different epitope. A fifth ovIL-1 alpha specific mAb, 5.01, had some characteristics of antibodies from both groups. While the combination of mAb 5.16 with any of 10.36, 10.49 and 10.82 was suitable for detection of ovIL-1 alpha in a sandwich immunoassay, the most sensitive detection of ovIL-1 alpha utilized mAb 10.82 for capture and a rabbit polyclonal anti-ovIL-1 alpha antiserum as the detecting antibody in combination with a HRPO-conjugated anti-rabbit Ig reagent. This combination of reagents had a detection limit for ovIL-1 alpha of 5 pg ml-1 and could detect both recombinant and native ovIL-1 alpha. Of the three ovIL-1 beta specific mAbs, (designated 2.93, 3.41 and 5.60) 3.41 and 5.60 recognized the same or a closely related epitope while 2.93 recognized an epitope more accessible on denatured ovIL-1 beta and proved most useful in Western blot analysis. Only mAb 3.41 was potent in neutralizing ovIL-1 beta biological activity in vitro. A sandwich immunoassay using mAb 3.41 to capture ovIL-1 beta and a rabbit polyclonal anti-ovIL-1 beta antiserum as the detecting antibody in combination with a HRPO-conjugated anti-rabbit Ig reagent had a sensitivity of 5 ng ml-1. The immunoassays were used to assess the relative proportions of IL-1 alpha and IL-1 beta in the supernatant of lipopolysaccharide stimulated ovine alveolar macrophages with IL-1 beta found to be the predominant secreted species of ovIL-1.

The immune response of sheep infected with larvae of the sheep blowfly Lucilia cuprina monitored via efferent lymph

Changes in lymphocyte traffic in efferent lymph from the prescapular lymph node of sheep were monitored during local primary and secondary infection with blowfly, Lucilia cuprina. During primary infections the response was characterised by an increase in the output of CD4+ T cells over CD8+ T cells for the first 48 h after wound initiation. By 72 h the output of CD8+ T cells exceeded that of CD4+ T cells. During secondary infections the increased output of CD8+ T cells was more pronounced and occurred earlier at approximately 48 h. The percentage of B lymphocytes as measured by sIg, CD45R and MHC class II expression increased at approximately 96-120 h after both primary and secondary infections, with the secondary response being greater than the primary. This increase in B cells corresponded with peak antibody titres recorded in the efferent lymph to a first instar antigen preparation as measured by ELISA. An increase in IFN-gamma and soluble IL-2 receptor was recorded after both primary and secondary infections, with the response after secondary infection being greater than that recorded after primary larval infections.

Production and in vivo use of recombinant ovine IL-1 beta as an immunological adjuvant

To determine the potential of ovine interleukin 1 (IL-1) as a vaccine adjuvant in sheep, we have expressed and purified recombinant ovine IL-1 beta (rovIL-1 beta) from bacterial cultures using a modified form of the ovine IL-1 beta cDNA. Adjuvant trials using the model protein avidin demonstrated that rovIL-1 beta when administered in association with a compound providing a slow-release mechanism, resulted in significant enhancement of specific serum antibody levels in both mice and sheep. In a dose-response experiment in sheep, intradermal immunization with avidin plus either 10 or 100 micrograms of rovIL-1 beta in aluminium hydroxide resulted in antibody levels four- to eightfold higher than immunizations without rovIL-1 beta. The addition of rovIL-1 beta also resulted in a more severe DTH response to avidin indicating that rovIL-1 beta is able to enhance both humoral and cell-mediated responses to avidin. The highest antibody titres were observed when sheep received rovIL-1 beta in both the primary and secondary immunizations although the addition of rovIL-1 beta in only one of the immunizations still resulted in a significant increase in antibody levels. Additional experiments showed that rovIL-1 beta and avidin must be administered in a site drained by the same lymph node for the adjuvant effect of rovIL-1 beta to be observed.

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.

Molecular cloning and characterization of a ruminant interleukin-6 cDNA

By hybridization with a human interleukin-6 (IL-6) cDNA fragment a corresponding ruminant (ovine) cDNA was isolated from a lipopolysaccharide (LPS)-stimulated alveolar macrophage library. The nucleotide sequence of the cDNA and the predicted amino acid sequence of the protein showed significant homology to the human and murine molecules. Ovine IL-6 cDNA encodes a polypeptide of 208 amino acids that, based on analysis of human IL-6, is processed to a protein of 180 amino acids. Northern blot analysis and the 7TD1 bioassay were used to analyse regulatory aspects of IL-6 production by primary ovine fibroblasts. Both LPS and recombinant ovine IL-1 alpha were shown to induce IL-6 mRNA with peak levels occurring at 1 h post-stimulation and declining thereafter. When fibroblasts were pretreated with cyclohexamide prior to stimulation the level of induction by LPS and IL-1 alpha increased dramatically and peak levels were observed at 5 h post-stimulation. The level of secreted IL-6 increased rapidly over the first 24 h and continued to increase over the next 48 h.

Characterization of the ovine interleukin-2 receptor-alpha chain: differential induction on precultured alpha beta and gamma delta T cells

A combination of concanavalin A (Con A)-stimulated ovine lymph node (LN) cells and Chinese hamster ovarian (CHO) cells stably transfected with the ovine interleukin-2 receptor-alpha (IL-2R alpha) chain cDNA (CHO IL-2R cells) were used in a differential immunization strategy to generate several monoclonal antibodies (mAb) against the ovine IL-2R alpha chain. The specificity of one of the mAb, designated mAb 9-14, for the ovine IL-2R alpha chain was demonstrated by its reactivity with Con A-stimulated LN cells and CHO IL-2R cells, immunoprecipitation of a 47,000 MW protein from CHO IL-2R cells and inhibition of IL-2-dependent proliferation of Con A-stimulated ovine LN cells. Examination of IL-2R alpha chain expression on resting lamb peripheral blood lymphocyte populations showed a high frequency of IL-2R alpha chain expression on CD4 T cells but not on CD8 T cells, CD45RA+ cells or gamma delta T cells, which comprise up to 60% of lamb peripheral blood T cells. The kinetics of IL-2R alpha chain induction on Con A-stimulated peripheral blood alpha beta and gamma delta T cells was compared. A rapid induction of IL-2R alpha chain expression on precultured gamma delta T cells but not alpha beta T cells was observed within 6 hr of Con A stimulation. A preculturing period was required to 'prime' gamma delta T cells for rapid responsiveness to Con A. Using appropriate inhibitors, we demonstrated that both transcription and translation events were required for rapid IL-2R expression on precultured gamma delta T cells and therefore the 'priming' of gamma delta T cells by in vitro culture did not involve an accumulation of IL-2R alpha chain mRNA or preformed receptors within these cells.

Molecular cloning, expression and characterization of the ovine IL-2R alpha chain

Interleukin-2 (IL-2) stimulates the proliferation of activated antigen-specific T cells through its interaction with high affinity receptors. This event is largely regulated by the inducible expression of the alpha-chain (CD25) which, in combination with the beta-chain and possibly additional chains, forms the high affinity IL-2 receptor (IL-2R) complex. From a concanavalin A (Con A)-activated ovine T-cell complementary DNA (cDNA) library we have isolated two cDNA clones which together constitute a 2650 base pair (bp) messenger RNA (mRNA) species encoding the ovine IL-2R alpha chain. The nucleotide sequence has high homology with analogous cDNA from other species and predicts a mature protein of 254 amino acids. In addition to the predominate 2.6 kilobase (kb) ovine IL-2R alpha chain mRNA species. Northern blot analysis of activated T-cell RNA revealed two larger mRNA species. The ovine IL-2R alpha chain cDNA was transfected into CHO cells and low affinity binding of human recombinant IL-2 demonstrated. Polyclonal antisera generated against the transfected cells cross-reacted with Con A-activated ovine lymphocytes. In addition these antisera were used to immunoprecipitate a unique 50,000 MW protein from the transfected cells. It is likely that this protein represents the expressed ovine IL-2R alpha chain cDNA which is heavily glycosylated as distinct from the 30,869 MW primary translation product. Southern blot analysis of ovine genomic DNA suggests that the ovine IL-2R alpha chain is encoded by a single copy gene.

Effects of tumour necrosis factor-alpha on growth hormone and interleukin 6 mRNA in ovine pituitary cells

The inflammatory cytokines tumour necrosis factor-alpha (TNF alpha), interleukin 1 (IL-1) and interleukin 6 (IL-6) have been demonstrated to influence pituitary hormone synthesis directly and via the hypothalamus. Furthermore, IL-6 is produced by some anterior pituitary cells suggesting a paracrine/autocrine role for this cytokine. We show that TNF alpha induces dispersed ovine pituitary cells to produce increased levels of growth hormone (GH) and IL-6 mRNA and secreted IL-6 in a dose and time dependent manner. TNF alpha at concentrations between 1-1000 U/ml increased GH and IL-6 mRNA, relative to control levels, by 5 h post-stimulation. For IL-6, TNF alpha increased specific mRNA at 5 h and 12 h but not 24 h post-stimulation. TNF alpha also induced secreted IL-6 to levels above that spontaneously secreted at all time points from 5 h to 48 h. Levels of common glycoprotein alpha-subunit and follicle stimulating hormone-beta (FSH beta) subunit mRNA were unaffected by TNF alpha. We conclude that TNF alpha can regulate both GH and IL-6 synthesis in dispersed ovine pituitary cells. The implications for paracrine/autocrine control of pituitary hormone synthesis in acute and chronic disease are discussed.

Characterisation of ovine alveolar macrophages: regulation of surface antigen expression and cytokine production

Regulation of ovine alveolar macrophage function by recombinant interferon gamma (rIFN gamma) and lipopolysaccharide (LPS) was investigated. Ten units per millilitre of rIFN gamma increased surface expression of MHC class I and class II (DR alpha, DP alpha, and DQ alpha) molecules but not other surface antigens examined. The upregulation of MHC class II expression was specifically blocked by rIFN gamma specific monoclonal antibodies and determination of a dose/response curve established that the minimum concentration of rIFN gamma required for increased class II expression was 0.1 U ml-1 and for increased class I expression, 1 U ml-1. Northern blot analysis indicated that rIFN gamma mediated increases in surface MHC class I and class II expression were due to increased levels of specific mRNA. Using Northern blot analysis and homologous human cDNA probes we failed to detect mRNA encoding the cytokines IL-1 alpha, IL-1 beta, and TNF alpha in RNA extracted from freshly isolated macrophages or macrophages cultured in medium alone. Exposure of macrophages to LPS increased production of all three cytokines although kinetics of upregulation varied. TNF alpha mRNA was induced to maximal levels within 1 h, declining thereafter. IL-1 alpha mRNA was detected at 1 h post stimulation with a maximal level at 5 h, but none at 24 h. In contrast, IL-1 beta mRNA was not detected until 5 h after stimulation with a low level remaining at 24 h. Dose response analysis indicated that LPS concentrations of 100 pg ml-1 induced detectable levels of TNF alpha mRNA while levels as low as 10 pg ml-1 induced secretion of bioactive IL-1. Analysis of the kinetics of secretion of bioactive IL-1 from LPS stimulated macrophages indicated that levels peaked at 24 h post stimulation.

Molecular cloning and characterization of ovine IL-1 alpha and IL-1 beta

Interleukin-1 (IL-1) is a cytokine with a wide range of effects on a variety of cell types. By hybridization with human IL-1 alpha and IL-1 beta cDNA probes, the corresponding ovine cDNAs were isolated from a stimulated alveolar macrophage cDNA library. The sequences of these cDNAs showed that ovine IL-1 alpha and IL-1 beta encode proteins of 268 and 266 amino acids, respectively, with both the nucleotide and amino acid sequences showing a high degree of homology with their human, mouse and bovine equivalents. In a mammalian COS cell-expression system these cDNAs produced biologically active IL-1. Further experiments demonstrated the importance of sequences within the 3' untranslated portion of the cDNAs in determining the level of expression of these molecules. The analysis of expression of IL-1 alpha- and IL-1 beta-specific mRNA in response to endotoxin, phorbol myristic acid (PMA) or PMA plus ionomycin revealed a distinct pattern of differential regulation of the two genes. From genomic analysis both IL-1 alpha and IL-1 beta appear to exist as single copies in the ovine genome.

Molecular cloning, expression and characterization of ovine TNF alpha

Tumour necrosis factor alpha (TNF alpha) is a cytokine with a wide range of effects on both lymphoid and non-lymphoid cell types. By hybridization with a human TNF alpha cDNA probe the corresponding ovine cDNA was isolated from a lipopolysaccharide (LPS) stimulated alveolar macrophage cDNA library. The sequence of the cDNA clone showed that ovine TNF alpha encodes a polypeptide of 234 amino acids that, based on analysis of human TNF alpha, is processed to a protein of 157 amino acids. The nucleotide and amino acid sequences showed a high degree of homology to the equivalent human and mouse molecules. In a mammalian COS cell expression system the ovine cDNA was found to encode a protein which was able to lyse actinomycin-D treated WEHI-164 cells and induce COS cells to produce and secrete interleukin 6 (IL-6). Further experiments demonstrated the importance of sequences within the 3' untranslated region of the cDNA in determining the level of expression of ovine TNF alpha. Northern blot analysis was used to analyse the kinetics of induction of ovine TNF alpha mRNA in alveolar macrophages stimulated with a variety of mitogens. Addition of LPS increased mRNA encoding TNF alpha at 1 h and 5 h but not 24 h post stimulation. In contrast, addition of phorbol myristic acid (PMA) led to increased TNF alpha mRNA at 5 h while the combination of PMA and ionomycin increased the level of specific mRNA detected at 1 h, 5 h and 24 h. From genomic analysis ovine TNF alpha appears to exist as a single copy.