Gamma interferon production by bovine gamma delta T cells following stimulation with mycobacterial mycolylarabinogalactan peptidoglycan

A large percentage of lymphocytes in the blood of cattle express the gamma delta T-cell receptor, but specific functions for these cells have not yet been clearly defined. There is evidence, however, that human, murine, and bovine gamma delta T cells have a role in the immune response to mycobacteria. This study investigated the ability of bovine gamma delta T cells to expand and produce gamma interferon (IFN-gamma) in response to stimulation with mycobacterial products. Bovine gamma delta T cells, isolated from the peripheral blood of healthy cattle, expanded following in vitro stimulation with live mycobacteria, mycobacterial crude cell wall extract, and Mycobacterium bovis culture filtrate proteins. In addition, purified gamma delta T cells, cocultured with purified monocytes and interleukin-2, consistently produced significant amounts of IFN-gamma in response to mycobacterial cell wall. The IFN-gamma-inducing component of the cell wall was further identified as a proteolytically resistant, non-sodium dodecyl sulfate-soluble component of the mycolylarabinogalactan peptidoglycan.     

Suppression of interferon gamma production in mice treated with carrageenan

Effects of carrageenan (CAR) treatment on the response of interferon (IFN) production in vivo and in vitro after stimulation with an IFN-gamma inducer, staphylococcal enterotoxin A (SEA), was investigated. The IFN-gamma production in mice stimulated with SEA was impaired after i.v. administration of a 20 mg/kg dose of CAR. Spleen cells (SC) from CAR-treated mice had decreased ability to produce IFN in vitro after stimulation with the same inducer. SC obtained from mice during the suppressive state inhibited IFN-gamma production when they were co-cultured with mononuclear cells prepared from spleens of untreated control mice. This suppressor cell activity could be removed from SC by an adherence technique to plastic surface. The SC with suppressor activity were not inactivated by treatments with monoclonal anti-Thy-1.2 antibody, anti-asialo GM1 antisera and anti-mouse immunoglobulin antisera followed by complement. The suppressive activity was detected in cell-free culture fluids of macrophage fractions containing suppressor cell activity. These results suggest that the decrease in IFN-gamma production in mice pretreated with CAR may associate with the presence of suppressor cells characterized to the monocyte/macrophage lineage.     

The role of heterologous helper cells in the production of gamma interferon by T-lymphocytes of human blood and lymph

The results of studies of the accessory functions of various heterologous cells in gamma interferon production by human blood and lymph T-lymphocytes are presented. It was shown that, in addition to autologous and allogeneic monocytes, the role of accessory cells may be played to some extent by xenogeneic (mouse) monocytes as well as human continuous cells of different origin. The degree of the accessory function was different in interaction of the accessory cells with T-lymphocytes from blood and lymph.     

Contribution of CD8(+) T cells to gamma interferon production in human tuberculosis

The proportions of peripheral blood mononuclear cells (PBMC), CD4(+) T cells, and CD8(+) T cells that produce gamma interferon (IFN-gamma) in response to Mycobacterium tuberculosis were markedly reduced in tuberculosis patients, particularly in those with severe disease. Depletion of CD4(+) but not CD8(+) cells prior to stimulation of PBMC with M. tuberculosis abolished IFN-gamma production. These results show that (i) IFN-gamma production by CD8(+) and CD4(+) cells correlates with the clinical manifestations of M. tuberculosis infection and (ii) IFN-gamma production by CD8(+) cells depends on CD4(+) cells.     

Functions of uterine natural killer cells are mediated by interferon gamma production during murine pregnancy.

The dominant lymphocytes in healthy human and murine implantation sites are pregnancy-associated uterine natural killer (uNK) cells. These cells produce 90% of pregnancy-induced, uterine interferon (IFN)- gamma, a cytokine that regulates expression of more than 0.5% of the mouse genome. Implantation sites in uNK cell-deficient and IFN- gamma -signal-disrupted mice display anomalies in decidua and its spiral arteries. Reconstitution of uNK cell-deficient females with bone marrow containing normal NK cell progenitors, establishes uNK cells and reverses the anomalies. Grafts from IFN- gamma(-/-)mice are restored uNK cells, but the uNK cells did not reverse the phenotypes. This review focuses on the functions of uNK cell-derived IFN- gamma and the genes that it may regulate in the pregnant uterus.     

Suppression of interferon production in mouse spleen cells by cytochalasin D.

Cytochalasin D is thought to impair microfilament function. The present study has investigated its effects on four different systems in which interferon is formed, namely (1) mouse fibroblasts induced with virus (2) mouse spleen cells induced with virus, or (3) with endotoxin or (4) by allogeneic stimulation. Cytochalasin D did not suppress formation of interferon by fibroblasts (L cells) or spleen cells stimulated with either HVJ or NDV. However it did suppress production of interferon by spleen cells in response to endotoxin or an allogeneic stimulation; here its action was apparently not on the secretion of interferon, but on some earlier event. It also suppressed the production of interferon by mouse spleen cells induced with HVJ if this had been u.v. irradiated for more than 15 min: this suggests that cytochalasin D sensitive structures do play some role in interferon production by mouse spleen cells when stimulated with HVJ, as well as when they are stimulated with endotoxin or an allogeneic stimulus.     

Suppression of polyclonal B cell activation by IgG-binding factors. Requirement for T cells

IgG-binding factors (IgG-BF) prepared from cell-free supernatant of human peripheral blood mononuclear cells interfere with the polyclonal activation of peripheral B cells by decreasing the numbers of IgG-containing cells and Ig plaque-forming cells. Using Nocardia opaca delipidated cell mitogen (NDCM), a T helper cell-independent polyclonal B cell activator, it was found that the suppressive effect of IgG-BF was no longer demonstrable after removal of T cells. In pokeweed mitogen-stimulated cultures, the suppression by IgG-BF required the presence of radiosensitive T cells. Selective depletion of OKT4+ or OKT8+ subsets in NDCM-stimulated cultures showed that IgG-BF required the presence of OKT4+ lymphocytes to induce suppression. It is concluded that the effect of human IgG-BF was mediated by one or several subsets of T cells.     

Interleukin-18 and gamma interferon production by oral epithelial cells in response to exposure to Candida albicans or lipopolysaccharide stimulation

Oral candidiasis is a collective name for a group of disorders caused by the dimorphic fungus Candida albicans. Host defenses against C. albicans essentially fall into two categories: specific immune mechanisms and local oral mucosal epithelial cell defenses. Since oral epithelial cells secrete a variety of cytokines and chemokines in response to oral microorganisms and since C. albicans is closely associated with oral epithelial cells as a commensal organism, we wanted to determine whether interleukin-18 (IL-18) and gamma interferon (IFN-gamma) were produced by oral epithelial cells in response to C. albicans infection and lipopolysaccharide (LPS) stimulation. Our results showed that IL-18 mRNA and protein were constitutively expressed by oral epithelial cells and were down-regulated by Candida infections but increased following LPS stimulation. Both C. albicans and LPS significantly decreased pro-IL-18 (24 kDa) levels and increased active IL-18 (18 kDa) levels. This effect was IL-1beta-converting-enzyme dependent. The increase in active IL-18 protein levels promoted the production of IFN-gamma by infected cells. No effect was obtained with LPS. Although produced only at an early stage, secreted IFN-gamma seemed to be a preferential response by oral epithelial cells to C. albicans growth. These results provide additional evidence for the contribution of oral epithelial cells to local (direct contact) and systemic (IL-18 and IFN-gamma production) defense against exogenous stimulation such as C. albicans infection or LPS stimulation.     

Comparison of antigen presentation by lymph node cells from protein and peptide-primed mice.

Lymph node cells from mice primed with peptides from the allergens Der p I and Der p II (the group I and II allergens of Dermatophagoides pteronyssinus) were unable to recall responses to the protein antigen when cultured in vitro despite being able to mount large responses to the peptides. The T cells could however recall responses to the protein when spleen-adherent cells were added into culture. Treating the spleen accessory cells with the monoclonal antibody (mAb) 33D1 and complement largely abrogated the protein response of peptide-primed T cells which indicates that dendritic cells were mainly responsible for the antigen-presenting function. If mice were primed with two injections of peptide the lymph node cells obtained could respond to both protein and peptides in vitro without the need for exogenous accessory cells. Using either negative depletion with the J11D mAb or positive purification, it was found that the presentation of protein antigen to lymph node T cells primed with either protein or peptide was limited to antigen-specific B cells. Peptide antigens could however be presented by both B and non-B populations. In one case the peptide 105-129 from Der p II which contains a T-cell epitope could not be shown to induce T-cell responses in the lymph node unless presentation was mediated by spleen-adherent or B-specific cells. These results are important for peptide-based immunomodulation and in interpreting results obtained from lymph node cultures.     

Gamma interferon is produced by human natural killer cells but not T cells during Staphylococcus aureus stimulation.

Gamma interferon (IFN-gamma) production from cultured human peripheral blood mononuclear cells was studied during stimulation with Staphylococcus aureus Cowan I or S. aureus Wood. IFN-gamma was specifically produced from CD16+ natural killer (NK) cells under stimulation by S. aureus Cowan I or Wood because these strains (i) induced IFN-gamma production exclusively from CD3-, CD4- CD8-, and CD16+ cells and (ii) induced CD69 and interleukin 2 (IL-2) receptor alpha expression on CD16+ cells without simultaneously augmenting CD71 or IL-2 receptor alpha on T cells. The effects of biological agents on the induction of S. aureus-induced IFN-gamma production paralleled those of S. aureus-induced CD69 expression on CD16+ cells: IL-2, IFN-alpha, and indomethacin augmented the S. aureus-induced IFN-gamma production, whereas IL-4, transforming growth factor beta 1, prostaglandin E2, and dexamethasone inhibited it. However, IFN-alpha was unique in that it did not induce IFN-gamma production from NK cells while it simultaneously augmented CD69 expression on NK cells, suggesting a unique pathway in the activation of NK cells. Thus, we may conclude that S. aureus-induced IFN-gamma production appears to faithfully represent NK cell function within peripheral blood mononuclear cells.     

Suppression of polyclonal immunoglobulin production by M-proteins shows isotype specificity

Monoclonal gammopathies are B cell neoplasms that are characterized by the presence of monoclonal immunoglobulins (M-proteins) in the serum. By an unknown mechanism, the normal polyclonal immunoglobulin levels are frequently reduced in sera of these patients. To assess the role of M-protein isotype in this effect, we used serum protein electrophoresis to quantitate monoclonal and polyclonal immunoglobulins in patients and we used serum immunofixation electrophoresis to determine their M-protein isotype. When divided into populations of 30 patients with IgG M-proteins (mean 2.5 g/dl) and 19 patients with IgM or IgA M-proteins (mean 2.6 g/dl), the mean polyclonal immunoglobulin level was significantly lower in the IgG M-protein population (0.4 g/dl) than the IgM/IgA population (0.8 g/dl). Patients with IgG M-proteins also had significantly lower polyclonal immunoglobulin levels when compared separately with the patients with either IgA or IgM paraproteins. Since the polyclonal immunoglobulin fraction is comprised mostly of IgG, these results give the first direct indication that IgG M-proteins have a greater suppressive effect on polyclonal IgG levels than do M-proteins of other isotypes. These findings suggest that an isotype-specific feedback mechanism could be involved in the normal regulation of serum IgG levels.     

Induction of antigen-specific regulatory T cells in the liver-draining celiac lymph node following oral antigen administration

Regulatory T cells are induced by oral administration of an antigen, but the physiological requirements and localization of the inductive sites are largely unknown. Using an adoptive transfer system of cells transgenic for ovalbumin T-cell receptor (OVA TCR tg), we found that antigen-specific CD4+ T cells were activated in the liver-draining celiac lymph node (CLN) shortly after ovalbumin feeding, and that a significantly higher proportion of the T cells in the CLN developed into the putative regulatory phenotype [co-expressing CD25 with the glucocortico-induced tumour necrosis factor (TNF) receptor family related gene (GITR), cytotoxic T-lymphocyte antigen (CTLA)-4 and CD103] than in Peyer's patches, the mesenteric and peripheral lymph nodes and the spleen. In addition, a particularly high level of expression of CD103 on the OVA-specific T cells in the CLN may favour homing to the epithelium of the intestine. While equally suppressive, OVA tg T cells isolated from the CLN of OVA-fed DO11.10 mice were less dependent on transforming growth factor (TGF)-beta for suppression than cells isolated from the peripheral and mesenteric lymph nodes, which indicates the involvement of an additional suppressive mechanism. The expression of FoxP3 was not up-regulated in any of the lymph node compartments studied. Our phenotypic and functional findings suggest that the induction of regulatory T cells in the CLN may be relevant in the control of the immune response to dietary antigens.     

Peripheral antigen display by lymph node stroma promotes T cell tolerance to intestinal self

The intestinal epithelium functions to absorb nutrients and to protect the organism against microbes. To prevent autoimmune attack on this vital tissue, T cell tolerance to intestinal self-antigens must be established. Central tolerance mechanisms involve medullary thymic epithelial cells (mTECs), which use endogenously expressed peripheral-tissue antigens (PTAs) to delete self-reactive thymocytes. The prevailing model for the induction of peripheral tolerance involves cross-presentation of tissue antigens by quiescent dendritic cells. Here we show that lymph node stromal cells present endogenously expressed PTAs to T cells. Moreover, antigen presentation by lymph node stroma is sufficient to induce primary activation and subsequent tolerance among CD8(+) T cells. Thus, lymph node stromal cells are functionally akin to mTECs and provide a direct strategy for purging the peripheral repertoire of self-reactive T cells.     

Concanavalin A-induced interferon gamma production by murine spleen cells and T cell lines. Lack of correlation with Lyt 1,2 phenotype

Concanavalin A(Con A)-induced interferon-gamma (IFN gamma) production by resting or preactivated murine spleen cells negatively selected with monoclonal antibodies specific for Lyt 1,2 antigens plus complement (C) and by interleukin 2(IL-2)-dependent T cell lines of different Lyt phenotype was studied. The data show that most of the IFN-gamma produced upon stimulation of resting spleen cells was a product of Lyt 1+2+ cells. Lyt 1-2+ cells were negative for IFN gamma production. When spleen cells that had been preactivated for 3 days with Con A were restimulated with Con A, Lyt 1+2+, Lyt 1+2- as well as Lyt 1-2+ cells produced IFN gamma in a relationship of approximately 5:3:1. In both cases the picture remained unaltered independently when the supernatants were harvested after 1, 3 or 5 days. Furthermore, two IL-2 dependent T cell lines were studied in regard to Con A-induced IFN gamma production. Line 1.3 was Thy 1+, Lyt 1-2+, whereas line 20.9. was Thy 1+, Lyt 1+2-. Both lines produced initially high titers of IFN gamma upon stimulation with Con A. After prolonged passage in vitro, however, they progressively lost the capacity to produce IFN gamma.