Dietary L-arginine modulates immunosuppression in broilers inoculated with an intermediate strain of infectious bursa disease virus

BACKGROUND

The effects of dietary l-arginine (Arg) on immunosuppression following infectious bursal disease virus (IBDV) inoculation in broiler chickens were evaluated. The design of this study was a 5 × 2 factorial arrangement (n = 5) with five Arg concentrations (starter: 9.9, 13.9, 17.6, 21.3 and 25.3 g kg(-1) ; grower-finisher: 9.5, 13.5, 17.1, 20.1 and 23.6 g kg(-1) ) with or without IBDV inoculation (IBDV or saline inoculation at 14 days). Chickens were sampled at 2, 4 and 6 days post-inoculation (DPI) and 42 days of age.

RESULTS

The IBDV inoculation decreased (P = 0.05) CD3(+) , CD4(+) , and CD8(+) T cell counts at 2 days post-inoculation (DPI) and monocyte counts at 6 DPI; and reduced (P < 0.05) bursal interleukin-1β (IL-1β) mRNA expression at 2 DPI and serum IL-6 concentration at 4 DPI. Increasing Arg concentration increased (P < 0.05) CD4(+) and CD8(+) T cell counts at 2 DPI, linearly increased (P = 0.05) CD3(+) T cell counts in IBDV-inoculated groups and monocyte counts in control groups at 4 DPI; increased (P < 0.05) serum IL-6 concentration in IBDV-inoculated groups at 2 DPI; and increased (P < 0.05) serum anti-IBDV antibody titres at 42 days of age.

CONCLUSION

Varying concentrations of Arg supplementation attenuated IBDV inoculation induced immunosuppression via modulating circulating T cell sub-populations.

Melatonin receptor subtypes Mel1a and Mel1c but not Mel1b are associated with monochromatic light-induced B-lymphocyte proliferation in broilers

This study determined the effects of melatonin (MEL) and its receptors on monochromatic light-induced bursal B-lymphocyte proliferation in broiler chickens. In vivo, green light (GL) enhanced the proliferation of B lymphocytes in bursas by 16.49% to 30.83% and the expression of MEL receptor subtypes 1a (Mel1a), Mel1b, and Mel1c receptors in bursas by 6.91% to 366.98% than other light colors. However, pinealectomy reduced these parameters and eliminated the differences between GL and other light groups. In vitro, the MEL-induced bursal B-lymphocyte proliferation was most suppressed by prazosin (P = 0.001, selective Mel1c antagonist), followed by luzindole (P = 0.022, nonselective Mel1a/Mel1b antagonist), but not by 4-phenyl-2-propionamideotetralin (P = 0.144, selective Mel1b antagonist). Similarly, dibutyryl-cyclic adenosine monophosphate (cAMP; analog of cAMP; P = 0.017) but not 8-(4-chloro-phenylthio)-2'-O-methyladenosine-3',5'-cyclic monophosphate (P = 0.736; activator of exchange protein directly activated by cAMP) significantly inhibited bursal B-lymphocyte proliferation. These results suggest that MEL mediates GL-induced bursal B-lymphocyte proliferation through Mel1c and Mel1a receptors but not Mel1b receptors by activating the cAMP/protein kinase A pathway.

Immunomodulatory roles and functional analysis of pre-B lymphocyte DT40 cells with the bursal-derived BSP-II treatment

The bursa of Fabricius, the acknowledged central humoral immune organ, is vital to B cell differentiation. However, the regulatory function of the bursal-derived peptide on avian B cell proliferation has not been reported. BSP-II is a recently reported bursal-derived bioactive peptide. In this paper, 75 days-old chicks were twice subcutaneously immunized with BSP-II and inactivated avian influenza virus (AIV, H(9)N(2) strain). It was proved that BSP-II induced a strongly AIV-specific HI antibody production in the immunized chicks. Also, BSP-II could enhance avian pre-B lymphocyte DT40 cell viability. To investigate the global patterns of gene expression in DT40 cells after BSP-II treatment, gene microarray was carried out. It was identified that the differentially expressed genes were involved in various pathways, of which six pathways were associated with signaling transductions, including ErbB signaling, MAPK signaling, Toll-like receptor signaling, Notch signaling, mTOR signaling, and Wnt signaling. Finally, RT-qPCR was used to confirm the microarray expression data. These results indicated the molecular basis of pre-B lymphocyte viability with BSP-II treatment, which provided a potential mechanism of the bursa of Fabricius on pre-B lymphocyte viability, differentiation, and development. These results are valid for the mechanism of the bursa of Fabricius on B lymphocytes development.

Characterization and immunomodulatory function comparison of various bursal-derived peptides isolated from the humoral central immune organ

The bursa of Fabricius (BF) is the acknowledged central immune organ, which is important to the B cell differentiation and antibody production. However, due to difficult purification, the immunomodulatory peptides from BF were little reported. In this study, the extract samples of BF were taken to a chromatographic analysis by RP-HPLC. Five novel low molecular weight peptides were isolated from BF, with amino acid sequences of YEYAY, RMYEE, GPPAT, AGCCNG, and RRL, and named as Bursal pentapeptide (BPP)-III, -IV, -V, and Bursal hexapeptide (BHP), and Bursal tripeptide (BTP), respectively. BSP-I, BSP-II, BPP-I and BPP-II are recently reported to be the bursal-derived bioactive peptides. In this paper, we analyzed the chemical formula and characteristics of these nine bursal-derived peptides. The immunization comparative experiment verified the different immunomodulatory activity of these nine bursal peptides on antibody and cytokine productions. Furthermore, the results showed that at reachable concentrations, BPP-II and BPP-I induced antibody productions, lymphocyte viabilities and cytokine responses in different dose-dependent manner in the immunized mice model, respectively. These results provided important orientations for the comprehensively understanding and study of the humoral central immune system of human, and provided a novel insight on the treatment of serious disease and immune improvement of human.

Bursopentine as a novel immunoadjuvant enhances both humoral and cell-mediated immune responses to inactivated H9N2 Avian Influenza virus in chickens

There is an urgent need for identification of a new adjuvant capable of selectively promoting an efficient immune response for use with vaccines and especially subunit vaccines. Our pervious study showed that Bursopentine (BP5) is a novel immunomodulatory peptide and has the ability to significantly stimulate an antigen-specific immune response in mice. In this study, the potential adjuvant activities of BP5 were examined in chickens by coinjection of BP5 and an inactivated avian influenza virus (AIV) (A/Duck/Jiangsu/NJ08/05 [AIV H9N2 subtype]). The results suggested that BP5 markedly elevated serum hemagglutination inhibition (HI) titers and antigen-specific antihemagglutinin (anti-HA) antibody (IgG) levels, induced both Th1 (interleukin 2 [IL-2] and gamma interferon [IFN-γ])- and Th2 (IL-4)-type cytokines, promoted the proliferation of peripheral blood lymphocytes, and increased populations of CD3(+) T cells and their subsets CD4(+) (CD3(+) CD4(+)) T cells and CD8(+) (CD3(+) CD8(+)) T cells. Furthermore, a virus challenge experiment revealed that BP5 contributes to protection against homologous avian influenza virus challenge by reducing viral replication in chicken lungs. This study indicates that the combination of inactivated AIVs and BP5 gives a strong immune response at both the humoral and cellular levels and implies that BP5 is a novel immunoadjuvant suitable for vaccine design.

Isolation, antiproliferation on tumor cell and immunomodulatory activity of BSP-I, a novel bursal peptide from chicken humoral immune system

The bursa of Fabricius (BF) is acknowledged as central humoral immune organ unique to birds. Our purpose was to identify the potential function of a novel bursal-derived bioactive peptide. A bursal septpeptide (BSP-I), EPASGMM, first isolated from BF, reduced MCF and Hela tumor cells proliferation, and enhanced antitumor factor p53 luciferase activity and protein expression. Further, we found the significantly immune inducing function of BSP-I on antigen-specific immune response in BALB/c mice intraperitoneally immunized with inactivated avian influence virus (AIV, H(9)N(2) subtype) vaccine, including of enhancing the antibody (IgG, the isotypes IgG1 and IgG2a) production, and stimulating cytokines IL-4 and IFN-γ level, and inducing T cell immunophenotyping and lymphocyte proliferation. These results suggested that as the bioactive peptide from avian humoral immune system, various biological function of BSP-I may have far-reaching implication on immune system significance, which might provide novel insight on linking between humoral immune system and development of effective immunotherapeutic strategies for treating human cancers diseases.

Isolation and potential immunological characterization of TPSGLVY, a novel bursal septpeptide isolated from the bursa of Fabricius

The bursa of Fabricius is central immune organ unique to birds, and the extract is immunocompetent in stimulating B cell differentiation and enhancing antibody production. However, except for bursin, the active peptides from the bursa of Fabricius are little reported. In the paper, a novel bursal septpeptide (BSP-II) with the amino acids sequence of TPSGLVY was identified and similar to the MGC53864 protein of Gallus gallus. We investigated the effects of BSP-II on the immune response in terms of the antibodies titers (IgG1 and IgG2alpha), the levels of interferon-gamma and interleukin-4 cytokines, spleen cell lymphocyte proliferation, and the T-lymphocyte subtype composition. It was noteworthy that BSP-II potentiates the Th1 and Th2-type immune responses in dose-dependent manner. BSP-II had specific enhancing effects on the hybridoma SP2/0 cell proliferation at two different serum concentrations (20% and 5%), but had no connection with the dose of BSP-II. The antibody secreting level of hybridoma SP2/0 cells rose in 5% and 20% serum when the concentrations of BSP-II increased. Also, BSP-II had effect on the viabilities of tumor cells (Hela and SP2/0). All the results indicated that BSP-II was able to significantly induce various immune responses and involved in the cell viability of different tumor cell lines. Our observations implied that BSP-II might be a novel biological active factor from the bursa of Fabricius with immunomodulatory activities.

Expression of pituitary adenylate cyclase-activating polypeptide in the primary lymphoid organs of the duck Anas platyrhynchos

The expression of pituitary adenylate cyclase-activating polypeptide (PACAP) was studied in the thymus and bursa of Fabricius of the duck Anas platyrhynchos, at different ages, using immunohistochemistry, Western blotting, RT-PCR and sequencing. In the thymus, PACAP immunoreactivity (-ir) was found in lymphoid cells. CD68/ and PGP 9.5/PACAP38 double labelling showed that PACAP was not expressed either in macrophages or in epithelial cells, suggesting that the PACAP-positive cells observed were lymphoid cells. Immunoreactive lymphocytes were observed in the interlobular septa. They increased in number with ageing. In the bursa, PACAP-ir was found in nerve fibres and in a few lymphoid cells. RT-PCR revealed PACAP mRNA expression in the thymus but not in the bursa. These results suggest that PACAP plays a role in the functions of the immune system in birds.

Effect of Infectious Bursal Disease Virus Insult on Iron, Copper, and Zinc Concentration in Liver, Bursa of Fabricius, Spleen, Pancreas, and Serum of Chickens

The effect of a systemic disease on the dynamics of iron, zinc, and copper in chickens fed ad libitum was examined by infecting 10-day-old specific pathogen-free chickens with infectious bursal disease virus (IBDV). Liver, bursa of Fabricius, pancreas, spleen, and serum were sampled in 10 controls and 10 challenged chickens at 3-day intervals postinfection (PI) for 15 days. The samples were analyzed using atomic absorption spectroscopy. Serum levels were similar to that reported in the literature. Concentrations of iron and zinc did not change significantly in the pancreas, but there was an increase in copper in infected pancreatic tissue on days 9 and 15 PI. Iron concentration in the spleen showed a significant increase on days 6, 9, and 15 PI, whereas zinc was only significantly increased on day 15 PI. There was no significant change in copper concentrations in the spleens of infected chickens vs. controls. This finding is in line with previously reported data. The results showed that the liver was not a major tissue where iron and zinc were sequestered, as previous data have shown in mammals. Instead, the bursa of Fabricius had significantly increased levels of both iron and zinc in infected tissue vs. control tissue from 9 days PI on. Furthermore, the bursa had increased levels of copper in the latter portion of the study. These findings suggest that the bursa of Fabricius rather than the liver is the major organ for metallic ion sequestering during IBDV infection.

Effects of dietary ratio of linoleic to linolenic acid on performance, antibody production, and in vitro lymphocyte proliferation in two strains of leghorn pullet chicks

The effects of dietary ratio of linoleic acid to linolenic acid on performance, mitogenic lymphocyte proliferation, and antibody production were evaluated in Leghorn pullets during a rigorous vaccination program. Diets were supplemented with flaxseed and corn oil to achieve 4 dietary ratios of linoleic acid to linolenic acid [17:1 (control), 8:1, 4:1, or 2:1]. Each diet was fed to HyLine Brown or W-36 pullets from 1 d to 16 wk of age. Day-old pullets were randomly assigned to 8 replicate cages with 12 pullets per cage; the density was reduced to 8 pullets per cage at 11 wk of age. Dietary treatments did not affect body weight, feed consumption, or pullet mortality. At 12 wk of age, an interaction between diet and strain (P < or = 0.004) showed Hy-Line W-36 pullets fed the 2:1 ratio had greater antibody production against Newcastle disease virus (NDV) vaccine than those fed diets with higher ratios. At wk 16, pullets fed ratios of 4:1 and 2:1 had the greatest antibody production against NDV vaccine. Antibody production against infectious bursal disease virus (IBDV) vaccine was also increased (P < 0.04) by ratios of 4:1 (2.244 optical density; OD) or 2:1 (2.508 OD) as compared with the control diet (1.576 OD). Hy-Line Brown pullets had greater antibody production against infectious bronchitis virus vaccine compared with Hy-Line W-36 pullets at 16 wk of age. These results indicate that feeding a reduced dietary ratio of linoleic to linolenic acid by adding flaxseed to the diets enhanced antibody response to NDV and IBDV vaccines without any negative effects on pullet performance.

Neurotrophins and the immune system

The neurotrophins are a family of polypeptide growth factors that are essential for the development and maintenance of the vertebrate nervous system. In recent years, data have emerged indicating that neurotrophins could have a broader role than their name might suggest. In particular, the putative role of NGF and its receptor TrkA in immune system homeostasis has become a much studied topic, whereas information on the other neurotrophins is scarce in this regard. This paper reviews what is known about the expression and possible functions of neurotrophins and their receptors in different immune tissues and cells, as well as recent data obtained from studies of transgenic mice in our laboratory. Results from studies to date support the idea that neurotrophins may regulate some immune functions. They also play an important role in the development of the thymus and in the survival of thymocytes.

[Analysis on the characteristics of histological location of bursin in immune organ of chicken and duck]

The distribution of Bursin in major immune organs such as bursa of Fabricius (BF), thymus (Th), Harderian gland(HG) and spleen(Sp) was investigated and compared in both chicken and duck by immuno-histochemical staining method with anti-Bursin monoclonal antibody (McAb)2F9-4. Its distributions in bone marrow(BM) and embryonic organs including BF, Th, BM, HG in chicken were also determined in addition to locating it in germinal center(GC) of Sp and lymphatic nodules of lymphonode in duck. The results showed clearly that Bursin was generally located in immune organs in both chicken and duck. However, its distributive regularity in chick was different from that appeared in duck. In addition, the biological significance on Bursin distribution in immune organs was discussed.

Differential cytoplasmic and whole cellular expression of histone H1 within the avian bursa of Fabricius

Bursal anti-steroidogenic peptide (BASP), purified from the chicken bursa of Fabricius (BF), has been previously demonstrated to be a potent and efficacious inhibitor of steroid hormone biosynthesis from chicken ovarian, and both mammalian and avian adrenal cells in vitro. Other studies have demonstrated that BASP can markedly reduce avian and mammalian mitogen-stimulated lymphocyte proliferation. Recent studies have indicated that BASP has a structural and functional relationship with histone H1. Immunohistochemical studies using a monoclonal antibody, which is known to recognize a common histone H1 epitope from several plant and animal species identified the protein within the cytoplasm and nucleus of distinct cells within both the cortex and medulla of all BF follicles. Additionally, epithelial cells within the BF expressed the protein strongly in the cytoplasm with reduced nuclear staining. In contrast, the same antibody did not recognize the protein in thymus of the same animals. The differential expression of histone H1 immunoreactivity within selected cells of the BF may support a previous proposed role of histone H1 in extranuclear and extracellular signaling in chickens and possibly other species.

Relationship of bursal anti-steroidogenic peptide (BASP) and histone H1

Previous in vitro research from our laboratory has demonstrated the existence of a protein purified from the chicken bursa of Fabricius, with potent antisteroidogenic and antiproliferative action on granulose cells and lymphocytes, respectively called Bursal anti-steroidogenic peptide (BASP). This protein is heat-labile, basic, and amino- and carboxy-terminus blocked. In highly purified form, the protein presents as a doublet on SDS-PAGE electrophoresis with an apparent MW of approximately 29 and approximately 32 kDa. Recently, Nanoflow Q-TOF Mass Spectrometry amino acid sequencing allowed determination of a convincing partial amino acid sequence, strongly suggesting a probable relationship of BASP with histone H1. Bursal cDNA expression library screening, using an antibody produced against BASP, also identified a clone with a sequence matching histone H1. Presently, we have demonstrated that SDS-PAGE electrophoresis of highly purified and bioactive BASP, and commercially-available calf thymus derived histone H1, produced similar doublets at approximately the same apparent MW, and that the electrophoretic profile of these 2 preparations were strikingly similar following 2 dimensional gel electrophoresis. The BASP doublet produced on SDS-PAGE was recognized by a commercially available monoclonal antibody recognizing a highly conserved region of histone H1. Furthermore, calf thymus histone H1 was found to suppress mitogen-stimulated chicken B-cell proliferation in a concentration-related manner, similar to the action of BASP. These data indicate that BASP shares substantial structural homology with, and may be identical to, histone H1.

A large database of chicken bursal ESTs as a resource for the analysis of vertebrate gene function

Chicken B cells create their immunoglobulin repertoire within the Bursa of Fabricius by gene conversion. The high homologous recombination activity is shared by the bursal B-cell-derived DT40 cell line, which integrates transfected DNA constructs at high rates into its endogenous loci. Targeted integration in DT40 is used frequently to analyze the function of genes by gene disruption. In this paper, we describe a large database of >7000 expressed sequence tags (ESTs) from bursal lymphocytes that should be a valuable resource for the identification of gene disruption targets in DT40. ESTs of interest can be recognized easily by online or keyword searches. Because the database reflects the gene expression profile of bursal lymphocytes, it provides valuable hints as to which genes might be involved in B-cell-specific processes related to immunoglobulin repertoire formation, signal transduction, transcription, and apoptosis. This large collection of chicken ESTs will also be useful for gene expression studies and comparative gene mapping within the chicken genome project. Details of the bursal EST sequencing project and access to database search forms can be found on the DT40 web site (http://genetics.hpi.uni-hamburg.de/dt40.html).

Efficacy of polyvinylpolypyrrolidone in reducing the immunotoxicity of aflatoxin in growing broilers

1. Protective action of an enzyme-linked polyvinylpolypyrrolidone (PVPP, Mycofix Plus) against the immunosuppressive effect of afatoxins (AF) was evaluated by determination of peripheral blood T-lymphocyte proportions and splenic plasma cell counts. Histological changes in lymphoid organs were also investigated by light microscopy. One-d-old broiler chicks (Hybro) received 2.5 mg/kg diet AF (83.06% AFB1, 12.98% AFB2, 2.84% AFG1, 1.12% AFG2) with or without PVPP (3g/kg diet) until 21 d of age. When compared with controls, AF treatment significantly decreased peripheral T-lymphocyte counts. AF caused a slight decrease in splenic plasma cell counts. The addition of PVPP to an AF-containing diet significantly increased T-lymphocyte counts. Splenic plasma cell counts were numerically intermediate between control and AF groups. 3. The dietary addition of PVPP to AF-free diet did not significantly alter either T-lymphocyte or splenic plasma cell counts.

Effect of bursal antisteroidogenic peptide (BASP) on chicken embryonic pituitary secretion of growth hormone (GH) and prolactin (PRL): evaluation in a reverse hemolytic plaque assay (RHPA)

Using the reverse hemolytic plaque assay described in the present investigation, a secretagogue activity of bursal antisteroidogenic peptide (BASP) for growth hormone (GH) or prolactin (PRL) secretion was observed in chicken Day 20e pituitary cell monolayers. Partially purified BASP (ppBASP), at all concentrations evaluated (0.25 BEQ/ml, 0.75 BEQ/ml, or 1.5 BEQ/ml), induced PRL secretion by isolated lactotrophs above (P < 0.05) basal levels during the 2- and 6-hr incubation. At the 18-hr time point, neither ppBASP nor vasoactive intestinal polypeptide (VIP) was efficacious (P < 0.05) in causing an elevation in PRL-secreting cells above basal levels. ppBASP, at all concentrations evaluated (0.25 BEQ/ml, 0.75 BEQ/ml, or 1.5 BEQ/ml), caused an increase in the percentage of GH-secreting cells above (P < 0.05) basal levels during the 18-hr incubation. When evaluating the 2-hr time point alone, ppBASP, at 0.75 or 1.5 BEQ/ml, significantly (P < 0.05) elevated the percentage of GH-secreting cells to above basal levels. After the 6-hr incubation, ppBASP at 0.25 or 0.75 BEQ/ml, was efficacious in causing elevated (P < 0.05) GH secretion above basal levels. The present study indicates a secretagogue activity of BASP on PRL or GH secretion by chicken embryonic anterior pituitary cells in vitro.

Cellular localization of growth hormone receptors/binding proteins in immune tissues

It is well established that the activity and proliferation of lymphoid cells and lymphoid organs are stimulated by growth hormone. These actions on lymphoid cells may be direct or mediated by actions on the epithelial and non-immune tissue cells that regulate immune function. The occurrence and cellular localization of growth hormone receptors in immune tissues has therefore been investigated to determine the target-sites of growth hormone action. Growth hormone receptor mRNA was first detected by Northern blotting in the spleen, bursa of Fabricius, and thymus of domestic fowl. In addition to the 4.4-kb transcript thought to encode the full-length growth hormone receptor, smaller transcripts of 2.8 kb and 1.0 kb, which may encode growth hormone-binding proteins, were also occasionally observed. Further analysis using the polymerase chain reaction revealed that mRNA sequences encoding the extracellular and intracellular domains of the growth hormone receptor were present in all tissues and highly homologous with hepatic transcripts. Translation of these transcripts also occurs in immune tissues, since immunoreactive growth hormone-binding proteins or growth hormone receptors of approximately 56 kDa were detected in hepatic, splenic, thymic, and bursal extracts. Immunocytochemistry of these tissues subsequently revealed that macrophages probably contain the bulk of this immunoreactivity, although some thymic medullary epithelial cells (including Hassall's corpuscles) and splenic ellipsoids and interdigitating cells were also immunoreactive. This immunoreactivity is present in immune tissues of newly hatched and adult chickens. Importantly, B-lymphocytes were rarely, if ever, immunoreactive, and T-lymphocytes containing growth hormone receptors or binding proteins were not observed. These results suggest that a number of primary (thymus and bursa) and secondary (spleen) lymphoid tissues in the chicken contain growth hormone receptors and are thus target-sites for growth hormone action. The distribution of growth hormone receptor/growth hormone-binding protein immunoreactivity in these tissues would further suggest that growth hormone plays a major role in macrophage proliferation and/or activity and may indirectly affect lymphocyte maturation and storage via effects on thymic and splenic stromal cells.

Dendritic cells in the bursal follicles and germinal centers of the chicken's caecal tonsil express vimentin but not desmin

BACKGROUND

Immunohistochemical studies with anti-vimentin and anti-desmin monoclonal antibodies were designed to determine the origin of bursal secretory dendritic cells (SDC) and follicular dendritic cells.

METHODS

The binding sites of anti-vimentin, anti-desmin, and anti-chicken-IgG specific monoclonal antibodies were visualized with a biotinylated anti-mouse-IgG, ABC Elite kit, and 4-chloronaphthol. Cells were double stained (anti-vimentin and rabbit anti-chicken-IgG Fc) to determine if the vimentin positive cells possessed surface IgG.

RESULTS

Vimentin positive cells were observed in the cortex and medulla of the bursa and germinal center and lymphoepithelial compartment of the caecal tonsil. The mesenchymal reticular cell, the basic supporting cell of the germinal center, was stained prominently by anti-vimentin and anti-desmin. Both antibodies stained the bursal cortex but only anti-vimentin bound the bursal secretory dendritic cell of the medulla. In addition to being vimentin positive and desmin negative, the bursal secretory dendritic cell possessed and the follicular dendritic cell appeared to possess IgG on their surfaces. In all the observations, B-cells were vimentin negative.

CONCLUSION

These studies suggest that follicular dendritic cells and mesenchymal reticular cells in the caecal tonsil's germinal centers may be functionally different cell populations while the bursal secretory dendritic cell and follicular dendritic cell of the caecal tonsil may have a common origin.

Effect of bursal anti-steroidogenic peptide (BASP) on cortisol biosynthesis in ACTH-stimulated canine adrenocortical carcinoma cells in vitro

Previous studies from our laboratory have demonstrated that bursal anti-steroidogenic peptide (BASP) inhibits progesterone biosynthesis from ovine luteinizing hormone-stimulated chicken ovarian granulosa cells. In the present investigation, we evaluated the efficacy of BASP for reducing cortisol secretion from normal canine adrenocortical cells and neoplastic adrenocortical cells from a dog with Cushing's syndrome. Treatment of adrenocortical cells derived from either normal healthy dogs or a cushingoid dog with adrenocorticotropic hormone (ACTH; 0-10 nM) caused an approximately two-fold increase in cortisol production from both normal or tumor derived adrenocortical cells. Small but significant decreases (up to 34%) in cortisol production were observed from normal and tumor derived canine adrenocortical cells when exposed to increasing concentrations of BASP (0.0-0.15 bursal equivalents; BEQ). Incubation of adrenocortical carcinoma cells or normal adrenocortical cells with ACTH (0-10 nM) and BASP (0.0-0.15 BEQ) increased cyclic AMP formation up to 2.5-fold. Interestingly, BASP suppressed basal cortisol production from tumor derived adrenocortical cells to normal levels when compared to the basal cortisol levels from normal derived adrenocortisol cells. Data from the present studies indicate that BASP is capable of suppressing basal and ACTH-stimulated cortisol production from normal or tumor derived adrenocortical cells in vitro. The possible clinical efficacy of homologous canine BASP on canine adrenal function or chicken BASP in other species of animals remains to be evaluated.

T-dependent areas in the chicken bursa of Fabricius: an immunohistological study

BACKGROUND

The so-called diffusely infiltrated lymphoid tissue of the chicken bursa of Fabricius was previously described as a T-dependent bursal area.

METHODS

We have analyzed immunohistologically its postnatal development by using a battery of mAbs, most of them raised specifically to chicken T cells, in order to characterize phenotypically the nature of its cell components, appearance, development, and possible functional significance.

RESULTS

Our results demonstrate that this tissue represents poorly developed lymphoid aggregates, the cell content reminiscent of that found in other lymphoid tissues occurring throughout the avian gut. The first lymphoid elements appear in this bursal area only after hatching, growing rapidly to reach the adult condition in the second week of postnatal life. They consist mainly of T lymphocytes, including principally. CD4+ TcR alpha V beta 1+ cells, which form cell groups and CD8+ cells, and TcR gamma delta+ lymphocytes, which predominate in the subepithelial area and within the epithelium. MHC Class II molecule-expressing cells and IgM-, IgG-, and IgA-positive B lymphocytes also occupy the subepithelial region.

CONCLUSIONS

We propose that the bursal diffusely infiltrated lymphoid tissue of the chicken represents gut-associated lymphoid tissue involved in mounting immune responses to antigens that reach the bursal lumen via the cloaca.

Activin beta A- and beta B-subunit expression in the developing chicken bursa of fabricius

The bursa of Fabricius (BF) is a site for B-lymphocyte maturation in birds. The BF is also known to function as an endocrine organ, with regulatory effects on steroid-secreting glands (testes, ovaries, and adrenal glands) during embryonic development. To study the possible involvement of the growth and differentiation factors, inhibins and activins, in bursal differentiation and function, the expression of inhibin/activin subunits in chicken BF was examined using specific antibodies against inhibin/activin alpha-, beta A-, and beta B-subunits. Bursae from chickens from 11 days of embryonic development until 22 weeks after hatching were studied. Immunoreactive beta A- and beta B-subunits were demonstrated in bursal epithelial cells throughout the time period studied. Immunoreactivities for both subunits were most intense and widespread from day 18 of embryonation until 1 week after hatching. Inhibin alpha-subunits were not detected. Partially different locations were shown for beta A- and beta B-subunits, suggesting different roles for activin-A (beta A beta A homodimer) and activin-B (beta B beta B homodimer) in bursal development and function. As activin beta A-subunit immunoreactivity was predominantly localized in medullary epithelia, it may be assumed that the developing B-cells within follicular medullae might be the target for activin-A action in the chicken BF. The most conspicuous site for activin-B production, on the other hand, was the follicle-associated epithelium, which is able to take up antigens from the cloacal environment and pass them to medullary cells. The data suggest that activin-A and -B may have different roles in modulating bursal microenvironment during B-lymphocyte differentiation. The possible role of bursal activins in the regulation of steroidogenesis in birds is discussed.

Influence of follicular maturation on inhibition of luteinizing hormone-, cyclic 3',5'-adenosine monophosphate-, and forskolin-stimulated progesterone production in chicken ovarian granulosa cells exposed to bursal anti-steroidogenic peptide

Previously, we demonstrated that a peptide from chicken bursa of Fabricius, bursal anti-steroidogenic peptide (BASP), inhibited LH-stimulated progesterone biosynthesis by granulosa cells from the two largest preovulatory follicles of the chicken ovary. In the present study, we investigated the influence of follicular maturation on the ability of BASP to inhibit granulosa cell steroidogenesis. Granulosa cells from the largest (F1), third largest (F3), and fifth largest (F5), preovulatory follicles of the laying hen were exposed to BASP in the presence or absence of ovine LH, forskolin, or dibutyryl-cAMP (db-cAMP). BASP (0.125 or 0.25 bursal equivalents [BEQ]) suppressed basal progesterone production in F5, but not in F1 or F3, granulosa cells. BASP suppressed LH-stimulated progesterone production in F1, F3, and F5 granulosa cells in a concentration-dependent manner; however, the lowest level (0.06 BEQ) did not suppress progesterone production in F5 granulosa cells. All levels of BASP suppressed forskolin-stimulated progesterone production in F1 granulosa cells, but only the highest level (0.25 BEQ) inhibited forskolin-stimulated steroidogenesis in F3 and F5 granulosa cells. Similar results were obtained with db-cAMP-stimulated granulosa cells. The inhibitory effects of BASP on F1, F3, and F5 granulosa cells were directly compared on a percentage basis. In the presence of each secret-agogue, the lowest level (0.06 BEQ) of BASP effectively suppressed progesterone synthesis in F1 and F3 but not F5 granulosa cells. At higher levels, there was no consistent difference in the ability of BASP to suppress stimulated progesterone production in granulosa cells at different stages of maturation.(ABSTRACT TRUNCATED AT 250 WORDS)

Bursal antisteroidogenic peptide alters the activity of steroidogenic enzymes in chicken granulosa cells

We have previously reported that a peptide from chicken bursa of Fabricius, bursal antisteroidogenic peptide (BASP), inhibits luteinizing hormone-stimulated progesterone biosynthesis by chicken ovarian granulosa cells. The objective of this study was to determine the site(s) of BASP inhibition within the steroidogenic pathway of chicken granulosa cells. The effects of BASP on key steroidogenic enzymes, including adenylyl cyclase (AC), phosphodiesterase, the cholesterol side-chain cleavage enzyme complex and 3 beta-hydroxysteroid dehydrogenase were determined. Luteinizing hormone (10 ng/tube) stimulated a fivefold increase in granulosa cell progesterone production that was inhibited by BASP (0.06, 0.12 or 0.25 bursal equivalents) in a dose-dependent manner. Luteinizing hormone stimulated a sixfold increase in cyclic 3',5'-adenosine monophosphate (cAMP) formation, and this increase was potentiated by BASP in a dose-dependent manner. In addition, BASP stimulated cAMP formation in the absence of luteinizing hormone without affecting progesterone production. The AC activator forskolin (0.1 mM) stimulated a 4.5-fold increase in progesterone synthesis, which was inhibited by BASP. In the presence of forskolin. BASP increased cAMP formation in a dose-dependent manner. A fivefold increase in progesterone synthesis induced by the phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine (1.0 mM) was inhibited by BASP. In the presence of 3-isobutyl-1-methylxanthine, BASP increased cAMP formation in a dose-dependent manner. Finally, 22(R)-hydroxycholesterol (250, 500, 1,000, or 2,500 ng/tube) or pregnenolone (50, 100, 200, or 500 ng/tube) resulted in up to 15- or 10-fold increases in progesterone production, respectively. Increasing concentrations of BASP caused a dose-dependent suppression of the conversion of 22(R)-hydroxycholesterol, but not pregnenolone, to progesterone. The inhibition of steroidogenesis by BASP is not associated with reduced cAMP levels, and BASP appears to strongly stimulate AC activity. In addition, these findings suggest that BASP may limit the availability of progesterone precursors by inhibiting the activity of the cholesterol side-chain cleavage enzyme complex.

[125I]iodomelatonin-binding sites in the bursa of Fabricius of birds: binding characteristics, subcellular distribution, diurnal variations and age studies

The melatonin-binding sites in membrane preparations of the bursa of Fabricius of birds were studied using [125I]iodomelatonin as a radioligand. The binding sites were stable, saturable, reversible and of high affinity. Scatchard analysis of specific binding revealed equilibrium binding constants (Kd) of (means +/- S.E.M.) 43.1 +/- 5.9, 73.3 +/- 7.6 and 35.3 +/- 4.8 pmol/l respectively at the mid-point of the light period (mid-light) in chickens, pigeons and quail, with a total number of binding sites (Bmax) of 1.23 +/- 0.15, 1.33 +/- 0.18 and 0.94 +/- 0.07 fmol/mg protein. The diurnal variation in [125I]iodomelatonin binding showed that the Bmax was 45, 115 and 70% higher at mid-light than at mid-dark in the bursae of chickens, pigeons and quail respectively. The Kd value determined from kinetic analysis was 49.0 +/- 6.4 pmol/l at mid-light in the chicken bursa. The [125I]iodomelatonin-binding sites of chicken bursal membranes had the following order of pharmacological affinities: 2-iodomelatonin > melatonin > 6-chloromelatonin > 6-hydroxymelatonin > N-acetyl-serotonin > 5-hydroxytryptamine, tryptamine, 5-methoxytryptophol, 1-acetylindole-3-carboxaldehyde, 3-acetylindole, L-tryptophan, 5-hydroxyindole-3-acetic acid, 5-hydroxytryptophan suggesting that the [125I]iodomelatonin-binding sites were highly specific for melatonin. The subcellular distribution of binding sites in the chicken bursa was in the following descending order: nuclear > mitochondrial > microsomal > cytosolic fraction. There was an age-related decrease in [125I]iodomelatonin-binding in chicken bursal membranes, with higher densities in the neonate.(ABSTRACT TRUNCATED AT 250 WORDS)

Detection and partial characterization of an anti-steroidogenic peptide from the humoral immune system of the chicken

Phenomenological association of alterations of immune system function at the time of puberty (e.g. involution of the chicken bursa of Fabricius) has led to postulation that the humoral immune system may negatively affect the hypothalamo-adenohypophyseal-gonadal axis of the neonate. Presently, we examined the effect of an acidic aqueous bursa of Fabricius extract, derived from prepubescent chickens, on in vitro basal and LH-stimulated progesterone biosynthesis by isolated ovarian granulosa cells of the largest preovulatory chicken follicles (F1 and F2). Crude extracts of < 5kDa and > 3kDa inhibited LH-stimulated progesterone secretion (P < 0.05). The bioactive component was observed to be heat labile and is sensitive to the endopeptidases chymotrypsin, trypsin and papain. The peptide is not sensitive to the exopeptidase, aminopeptidase M. Partial purification by reversed phase HPLC resulted in a fraction capable of inhibiting in vitro steroidogenesis. This fraction suppressed LH-stimulated progesterone biosynthesis to approximately basal levels (79% suppression). Following removal of the peptide, granulosa cells were capable of LH-stimulated progesterone biosynthesis similar to control cells. Bursal extract significantly inhibited cAMP analog-stimulated progesterone biosynthesis. These data indicate that the anti-steroidogenic peptide derived from the chicken bursa of Fabricius is a single heat labile, amino terminally blocked peptide with bioactivity independent of the gonadotropin receptor of the granulosa cell.

The Turkey Major Histocompatibility Complex: Identification of Class II Genotypes by Restriction Fragment Length Polymorphism Analysis of Deoxyribonucleic Acid

Using a chicken Class II MHC clone in Northern blot analysis, tissue-specific expression of turkey Class II MHC genes was observed in the embryonic bursa of Fabricius as well as in the adult spleen. In contrast, there was no detectable expression in the embryonic liver, brain, or spleen. Southern blot analysis of BamHI-digested turkey DNA revealed two restriction fragment length polymorphism (RFLP) patterns that did not deviate significantly from single-gene Mendelian inheritance. Further analysis of PvuII-digested DNA from 325 turkeys showed four distinct RFLP patterns that segregated within the turkey lines studied. Because the chicken Class II MHC clone hybridized specifically to mRNA in immune-associated tissues, and because it identified polymorphisms among turkeys, the chicken clone is suggested to identify four turkey Class II MHC genotypes. The current study provides good evidence that RFLP analysis of DNA can be used as a means for molecular genotyping at the MHC in turkeys.

Differentiation of bursal secretory-dendritic cells studied with anti-vimentin monoclonal antibody

Embryonic and posthatched differentiation of bursal secretory dendritic cells, which express vimentin intermediate filaments, were studied with anti-vimentin (clone 3B4) and anti-cytokeratin (clone Lu5) monoclonal antibodies. Anti-cytokeratin staining revealed that medullary reticular epithelial cells formed a continuous network at every age, whereas the vimentin positive cells were single and showed dendritic appearance. On the basis of location, number, shape, polarized appearance, and Ia staining, the vimentin-positive cells and secretory dendritic cells appeared to be the same cell. Secretory dendritic cell precursors entered the bursal epithelium between 11 and 13 days of embryogenesis. The first vimentin positive cell appeared in the bud of 14-day embryos. Bud formation preceded the appearance of vimentin-positive cells. These observations suggested that the secretory dendritic cell precursor did not express vimentin when it entered the epithelium. Between 15 days of embryogenesis and 2 weeks of posthatch development, the changes in vimentin staining pattern revealed a cytological differentiation of the vimentin-positive cell. During rapid bursal growth, the number of secretory dendritic cells (vimentin-positive cells) increased about 18 times possibly by proliferation of vimentin-negative precursors in the epithelial arches of the corticomedullary border.

The effects of stress, Escherichia coli, dietary ethylenediaminetetraacetic acid, and their interaction on tissue trace elements in chicks

The present study determined effects of Escherichia coli infection, crowding stress, and EDTA supplementation on Cu, Fe, and Zn levels in the serum, liver, bursa of Fabricius, and spleen of chickens. Organ weights as a percentage of BW were affected by treatments prior to and after infection. Liver and spleen weights as a percentage of BW increased with infection but bursa weight decreased. One week of stress increased hepatic Cu, but 3 wk of EDTA ingestion increased serum Cu and serum, hepatic, bursal, and splenic Fe. These elemental changes resulting from EDTA may have predisposed the chicks to a higher mortality rate from E. coli compared with controls. Peak mortality occurred 2 days after infection, coincident with an increased serum Cu, decreased serum and bursal Fe and Zn, and increased hepatic and splenic Zn. At 7 days postinfection, recovering chicks experienced decreased hepatic Fe, elevated hepatic Zn, decreased bursal Cu, Fe, and Zn, and increased splenic Cu, Fe, and Zn. The current study demonstrates the interactive effects of EDTA, stress, and E. coli infection on serum and organ trace element concentration.

Effect of dietary fats on the fatty acid compositions of serum and immune tissues in chickens

The purpose of the present study was to measure the effect of dietary fat source on the fatty acid composition of immune cells in chickens. One-day-old female chicks were fed corn and soybean meal-based diets containing 7% of either lard, corn oil, canola oil, linseed oil (LO), or menhaden fish oil (FO). After being fed experimental diets for 3 to 4 wk, samples of serum, thymus glands, bursa of Fabricius glands, and splenocytes were collected. All samples were frozen and stored at -80 C until lipid analysis. Results indicate that the fatty acid composition of the sera and immune tissues of chickens reflected the fat in the diet. The relative content of long-chain polyunsaturated fatty acids varied considerably among immune tissues, with, from greatest to least, spleen, bursa, and thymus. The young chick demonstrated a substantial capacity to elongate and desaturate linoleic (C18:2n-6) and alpha-linolenic acids (C18:3n-3). Feeding chicks fats rich in n-3 fatty acids (e.g., LO or FO) decreased significantly (P less than .05) the level of arachidonic acid (C20:4n-6) present in the serum and immune tissues by 50 to 75%. The levels of eicosapentaenoic acid (EPA, C20:5n-3) and docosahexaenoic acid (DHA, C20:6n-3) were substantially increased (P less than .05) by FO and LO feeding. However, LO, which is rich in C18:3n-3, was generally only one-half to one-quarter as effective as FO in elevating EPA and DHA levels in immune tissues. The implications for these changes in serum and immune tissue fatty acid profiles are discussed briefly.

S-100 immunoreactive cells in the spleen and bursa of Fabricius of broiler chickens

The distribution of S-100 protein in spleens and bursae of Fabricius of broiler chickens with various diseases was investigated by an immunohistochemical method with antiserum to bovine S-100 protein. S-100 protein-positive cells were found in six cases of 34 chickens. In spleens, S-100 protein was detected in reticular cells in the ellipsoids of the sheathed arteries and eosinophilic granulocytes. Follicular dendritic cells in germinal centres were also S-100 protein-positive. In the bursa, reticular cells of the follicles and eosinophilic granulocytes in the follicular cortex and surface epithelium were positive for S-100 protein. The evidence suggests that S-100 protein may be involved in diseases of chickens.