Modulation of chicken macrophage effector function by T(H)1/T(H)2 cytokines

Regulation of macrophage activity by T(H)1/2 cytokines is important to maintain the balance of immunity to provide adequate protective immunity while avoiding excessive inflammation. IFN-γ and IL-4 are the hallmark T(H)1 and T(H)2 cytokines, respectively. In avian species, information concerning regulation of macrophage activity by T(H)1/2 cytokines is limited. Here, we investigated the regulatory function of chicken T(H)1 cytokines IFN-γ, IL-18 and T(H)2 cytokines IL-4, IL-10 on the HD11 macrophage cell line. Chicken IFN-γ stimulated nitric oxide (NO) synthesis in HD11 cells and primed the cells to produce significantly greater amounts of NO when exposed to microbial agonists, lipopolysaccharide, lipoteichoic acid, peptidoglycan, CpG-ODN, and poly I:C. In contrast, chicken IL-4 exhibited bi-directional immune regulatory activity: it activated macrophage NO synthesis in the absence of inflammatory agonists, but inhibited NO production by macrophages in response to microbial agonists. Both IFN-γ and IL-4, however, enhanced oxidative burst activity of the HD11 cells when exposed to Salmonella enteritidis. IL-18 and IL-10 did not affect NO production nor oxidative burst in HD11 cells. Phagocytosis and bacterial killing by the HD11 cells were not affected by the treatments of these cytokines. Infection of HD11 cells with S.enteritidis was shown to completely abolish NO production regardless of IFN-γ treatment. This study has demonstrated that IFN-γ and IL-4 are important T(H)1 and T(H)2 cytokines that regulate macrophage function in chickens.     

Differential regulation of central nervous system autoimmunity by T(H)1 and T(H)17 cells

Multiple sclerosis is an inflammatory, demyelinating disease of the central nervous system (CNS) characterized by a wide range of clinical signs. The location of lesions in the CNS is variable and is a crucial determinant of clinical outcome. Multiple sclerosis is believed to be mediated by myelin-specific T cells, but the mechanisms that determine where T cells initiate inflammation are unknown. Differences in lesion distribution have been linked to the HLA complex, suggesting that T cell specificity influences sites of inflammation. We demonstrate that T cells that are specific for different myelin epitopes generate populations characterized by different T helper type 17 (T(H)17) to T helper type 1 (T(H)1) ratios depending on the functional avidity of interactions between TCR and peptide-MHC complexes. Notably, the T(H)17:T(H)1 ratio of infiltrating T cells determines where inflammation occurs in the CNS. Myelin-specific T cells infiltrate the meninges throughout the CNS, regardless of the T(H)17:T(H)1 ratio. However, T cell infiltration and inflammation in the brain parenchyma occurs only when T(H)17 cells outnumber T(H)1 cells and trigger a disproportionate increase in interleukin-17 expression in the brain. In contrast, T cells showing a wide range of T(H)17:T(H)1 ratios induce spinal cord parenchymal inflammation. These findings reveal critical differences in the regulation of inflammation in the brain and spinal cord.     

A brief history of T(H)17, the first major revision in the T(H)1/T(H)2 hypothesis of T cell-mediated tissue damage

For over 35 years, immunologists have divided T-helper (T(H)) cells into functional subsets. T-helper type 1 (T(H)1) cells-long thought to mediate tissue damage-might be involved in the initiation of damage, but they do not sustain or play a decisive role in many commonly studied models of autoimmunity, allergy and microbial immunity. A major role for the cytokine interleukin-17 (IL-17) has now been described in various models of immune-mediated tissue injury, including organ-specific autoimmunity in the brain, heart, synovium and intestines, allergic disorders of the lung and skin, and microbial infections of the intestines and the nervous system. A pathway named T(H)17 is now credited for causing and sustaining tissue damage in these diverse situations. The T(H)1 pathway antagonizes the T(H)17 pathway in an intricate fashion. The evolution of our understanding of the T(H)17 pathway illuminates a shift in immunologists' perspectives regarding the basis of tissue damage, where for over 20 years the role of T(H)1 cells was considered paramount.     

T(H)1 cells control themselves by producing interleukin-10

Inflammatory T helper 1 (T(H)1)-cell responses successfully eradicate pathogens, but often also cause immunopathology. To minimize this deleterious side-effect the anti-inflammatory cytokine interleukin-10 (IL-10) is produced. Although IL-10 was originally isolated from T(H)2 cells it is now known to be produced by many cell types. Here, we discuss the recent evidence that shows that T(H)1 cells are the main source of IL-10 that controls the immune response against Leishmania major and Toxoplasma gondii infection.     

Functions of T cells in asthma: more than just T(H)2 cells

Asthma has been considered a T helper 2 (T(H)2) cell-associated inflammatory disease, and T(H)2-type cytokines, such as interleukin-4 (IL-4), IL-5 and IL-13, are thought to drive the disease pathology in patients. Although atopic asthma has a substantial T(H)2 cell component, the disease is notoriously heterogeneous, and recent evidence has suggested that other T cells also contribute to the development of asthma. Here, we discuss the roles of different T cell subsets in the allergic lung, consider how each subset can contribute to the development of allergic pathology and evaluate how we might manipulate these cells for new asthma therapies.     

Selective C-Rel activation via Malt1 controls anti-fungal T(H)-17 immunity by dectin-1 and dectin-2

C-type lectins dectin-1 and dectin-2 on dendritic cells elicit protective immunity against fungal infections through induction of T(H)1 and T(H)-17 cellular responses. Fungal recognition by dectin-1 on human dendritic cells engages the CARD9-Bcl10-Malt1 module to activate NF-κB. Here we demonstrate that Malt1 recruitment is pivotal to T(H)-17 immunity by selective activation of NF-κB subunit c-Rel, which induces expression of T(H)-17-polarizing cytokines IL-1β and IL-23p19. Malt1 inhibition abrogates c-Rel activation and T(H)-17 immunity to Candida species. We found that Malt1-mediated activation of c-Rel is similarly essential to induction of T(H)-17-polarizing cytokines by dectin-2. Whereas dectin-1 activates all NF-κB subunits, dectin-2 selectively activates c-Rel, signifying a specialized T(H)-17-enhancing function for dectin-2 in anti-fungal immunity by human dendritic cells. Thus, dectin-1 and dectin-2 control adaptive T(H)-17 immunity to fungi via Malt1-dependent activation of c-Rel.     

A rat anti-mouse T4 monoclonal antibody (H129.19) inhibits the proliferation of Ia-reactive T cell clones and delineates two phenotypically distinct (T4+, Lyt-2,3-, and T4-, Lyt-2,3+) subsets among anti-Ia cytolytic T cell clones

Hybridoma H129 .19 was derived by fusion between spleen cells of a Lou / Ws1 rat immunized with an Lyt-1+,2- anti-I-Ak cytolytic T lymphocyte (CTL) clone and the nonsecreting myeloma X63-Ag8.653. The monoclonal antibody (mAb) H129 .19 (IgG2a, kappa) was selected for its capacity to inhibit the lytic potential of the immunizing clone. H129 .19 identified a monomorphic determinant on a 55 m.w. murine T cell differentiation antigen, which appeared to be homologous to the human T4 molecule in that: 1) H129 .19 reacted with 80% adult thymocytes, with a subset of splenic T cells, and with the interleukin 2 (IL 2)-producing EL4 thymoma; 2) The mAb bound to and inhibited the IL 2 production and the proliferation of various allo- or soluble antigen-reactive T cell clones that recognized restriction or activating determinants on the I-A or I-E molecules, respectively; 3) H129 .19 did not inhibit the proliferation and/or cytolysis of Lyt-2,3+ T cells specific for class I MHC antigen; and 4) Among six anti-Iak CTL clones examined in this study, the mAb H129 .19 reacted with two I-Ak-specific, Lyt-2,3- clones on which it exerted strong cytolysis inhibiting effect at the effector cell level. By contrast, two other anti-I-Ak and two anti-I-Ek CTL clones were found to express the Lyt-2,3+,T4- cell surface phenotype. The cytolytic potential of the latter clones was not inhibited by anti-Lyt-2,3 mAb. These studies strongly suggest that the mouse T4 molecule facilitates the recognition of class II MHC antigen by most but not all T cells.     

Identification of Baicalin as an immunoregulatory compound by controlling T(H)17 cell differentiation

T(H)17 cells have been implicated in a growing list of inflammatory disorders. Antagonism of T(H)17 cells can be used for the treatment of inflammatory injury. Currently, very little is known about the natural compound controlling the differentiation of T(H)17 cells. Here, we showed that Baicalin, a compound isolated from a Chinese herb, inhibited T(H)17 cell differentiation both in vitro and in vivo. Baicalin might inhibit newly generated T(H)17 cells via reducing RORγt expression, and together with up-regulating Foxp3 expression to suppress RORγt-mediated IL-17 expression in established T(H)17 cells. In vivo treatment with Baicalin could inhibit T(H)17 cell differentiation, restrain T(H)17 cells infiltration into kidney, and protect MRL/lpr mice against nephritis. Our findings not only demonstrate that Baicalin could control T(H)17 cell differentiation but also suggest that Baicalin might be a promising therapeutic agent for the treatment of T(H)17 cells-mediated inflammatory diseases.     

SOCS-3 regulates onset and maintenance of T(H)2-mediated allergic responses

Members of the suppressor of cytokine signaling (SOCS) family are involved in the pathogenesis of many inflammatory diseases. SOCS-3 is predominantly expressed in T-helper type 2 (T(H)2) cells, but its role in T(H)2-related allergic diseases remains to be investigated. In this study we provide a strong correlation between SOCS-3 expression and the pathology of asthma and atopic dermatitis, as well as serum IgE levels in allergic human patients. SOCS-3 transgenic mice showed increased T(H)2 responses and multiple pathological features characteristic of asthma in an airway hypersensitivity model system. In contrast, dominant-negative mutant SOCS-3 transgenic mice, as well as mice with a heterozygous deletion of Socs3, had decreased T(H)2 development. These data indicate that SOCS-3 has an important role in regulating the onset and maintenance of T(H)2-mediated allergic immune disease, and suggest that SOCS-3 may be a new therapeutic target for the development of antiallergic drugs.     

2H1--a novel antigen involved in T lymphocyte triggering

A mAb anti-2H1, was produced against PHA-activated T cells from a lower primate, Aotus trivirgatus. Anti-2H1 reacted with 90% of peripheral T cells but was found to react with only 10% of thymocytes and some, but not all, leukemic T cell lines. 2H1 expression was dramatically increased when thymic cells were activated by Con A plus PMA. In contrast, anti-2H1 did not react with B cells, macrophages, null cells, or hematopoietic stem cell lines. More importantly, anti-2H1 antibody can induce T cell activation and proliferation in synergy with PMA or anti-T11(3). SDS-PAGE analysis of polypeptides immunoprecipitated with anti-2H1 showed two major polypeptides of 140 and 105 kDa. Thus, the 2H1 Ag can be distinguished from T3, T11, and 9.3 Ag. These results indicate that the 2H1 Ag appears to be involved in the activation of T lymphocytes.     

H2-M3-restricted T cells participate in the priming of antigen-specific CD4+ T cells

H2-M3-restricted CD8+ T cells provide early protection against bacterial infections. In this study, we demonstrate that activated H2-M3-restricted T cells provide early signals for efficient CD4+ T cell priming. C57BL/6 mice immunized with dendritic cells coated with the MHC class II-restricted listeriolysin O peptide LLO(190-201) (LLO) generated CD4+ T cells capable of responding to Listeria monocytogenes (LM) infection. Inclusion of a H2-M3-restricted formylated peptide fMIGWII (fMIG), but not MHC class Ia-restricted peptides, during immunization with LLO significantly increased IFN-gamma-producing CD4+ T cell numbers, which was associated with increased protection against LM infection. Studies with a CD4+ T cell-depleting mAb indicate that the reduction in bacterial load in fMIG plus LLO immunized mice is likely due to augmented numbers of LLO-specific CD4+ T cells, generated with the help of H2-M3-restricted CD8+ T cells. We also found that augmentation of LLO-specific CD4+ T lymphocytes with H2-M3-restricted T cells requires presentation of LLO and fMIG by the same dendritic cells. Interestingly, the augmented CD4+ T cell response generated with fMIG also increased primary LM-specific responses by MHC class Ia-restricted CD8 T cells. Coimmunization with LLO and fMIG also increases the number of memory Ag-specific CD4+ T cells. We also demonstrate that CD8 T cells restricted to another MHC class Ib molecule, Qa-1, whose human equivalent is HLA-E, are also able to enhance Ag-specific CD4+ T cell responses. These results reveal a novel function for H2-M3- and Qa-1-restricted T cells; provision of help to CD4+ Th cells during the primary response.     

Histamine H(1) receptor signaling regulates effector T cell responses and susceptibility to coxsackievirus B3-induced myocarditis

Susceptibility to autoimmune myocarditis has been associated with histamine release by mast cells during the innate immune response to coxsackievirus B3 (CVB3) infection. To investigate the contribution of histamine H(1) receptor (H(1)R) signaling to CVB3-induced myocarditis, we assessed susceptibility to the disease in C57BL/6J (B6) H(1)R(-/-) mice. No difference was observed in mortality between CVB3-infected B6 and H(1)R(-/-) mice. However, analysis of their hearts revealed a significant increase in myocarditis in H(1)R(-/-) mice that is not attributed to increased virus replication. Enhanced myocarditis susceptibility correlated with a significant expansion in pathogenic Th1 and Vγ4(+) γδ T cells in the periphery of these animals. Furthermore, an increase in regulatory T cells was observed, yet these cells were incapable of controlling myocarditis in H(1)R(-/-) mice. These data establish a critical role for histamine and H(1)R signaling in regulating T cell responses and susceptibility to CVB3-induced myocarditis in B6 mice.     

Rac2-deficient mice display perturbed T-cell distribution and chemotaxis,but only minor abnormalities in T(H)1 responses

The haematopoietic-specific RhoGTPase, Rac2, has been indirectly implicated in T-lymphocyte development and function, and as a pivotal regulator of T Helper 1 (T(H)1) responses. In other haematopoietic cells it regulates cytoskeletal rearrangement downstream of extracellular signals. Here we demonstrate that Rac2 deficiency results in an abnormal distribution of T lymphocytes in vivo and defects in T-lymphocyte migration and filamentous actin generation in response to chemoattractants in vitro. To investigate the requirement for Rac2 in IFN-gamma production and TH1 responses in vivo, Rac2-deficient mice were challenged with Leishmania major and immunized with ovalbumin-expressing cytomegalovirus.Despite a minor skewing towards a T(H)2 phenotype, Rac2-deficient mice displayed no increased susceptibility to L. major infection. Cytotoxic T-lymphocyte responses to cytomegalovirus and ovalbumin were also normal. Although Rac2 is required for normal T-lymphocyte migration, its role in the generation of T(H)1 responses to infection in vivo is largely redundant.     

Histamine type I (H1) receptor radioligand binding studies on normal T cell subsets, B cells, and monocytes

We have documented a single, specific binding site for [3H]pyrilamine on normal human T helper, T suppressor, B cells, and monocytes. The binding of the radioligand to its receptor is reversible with cold H1 antagonist, saturates at 40 to 60 nM, and binding equilibrium is achieved in 2 to 4 min. Using a computer program (Ligand), we calculated the dissociation constants, binding capacities, and numbers of receptors per cell for each of the different cell types. Monocytes were found to have the highest affinity (mean KD +/- SD; 3.8 +/- 4.8 nM) for [3H]pyrilamine, followed by T helper cells (KD = 5.0 +/- 6.6 nM), B cells (KD = 14.2 +/- 2.0 nM), and T suppressor cells (KD = 44.6 +/- 49.4 nM). T suppressor cells were found to express the higher number of H1 receptors per cell (35,697 +/- 15,468), followed by B cells (10,732 +/- 9060), T helper cells (6838 +/- 8167), and monocytes (5589 +/- 2266). The kinetics of binding for this radioligand was carried out in resting and mitogen-stimulated T cells over a 48-hr period. We found that the binding affinity for [3H]pyrilamine increased over the 48-hr period, whereas the number of receptors per T cell was essentially unchanged. In contrast, T cells stimulated with Con A or PHA were shown to have a greater than fourfold increase in the number of receptors per cell, whereas the binding affinity for [3H]pyrilamine decreased over the 48-hr period. Preincubation of T cells with unlabeled histamine before carrying out the radioligand binding assay resulted in a decrease in the binding affinity of the receptors to [3H]pyrilamine, but the number of receptors per cell did not change significantly. Although the function of H1 receptors on T cells, B cells, and monocytes has not been completely defined, this receptor has the potential of playing an important role in modulating the immune response.     

Augmentation of T(H)-1 type response by immunoactive AT oligonucleotide from lactic acid bacteria via Toll-like receptor 9 signaling

Toll-like receptor 9, which is expressed on the surface of antigen presenting cells and which was recently identified in the cytoplasmic follicle, recognizes bacterial CpG oligodeoxynucleotides (ODNs), resulting in the induction of a potent immune response. However, in our previous study, we found that TLR9 potentially recognizes not only CpG ODN but also non-CpG ODN such as AT ODN. Therefore, in the present study, to investigate this possibility, we elucidated the effects of AT ODN on T(H)-1, T(H)-2 type cytokine induction via TLR9 by real-time quantitative PCR analysis and ELISA of the swine TLR9 transfectant. The results demonstrated that the T(H)-1 type cytokines such as interleukin (IL)-12p70 and interferon (IFN)-gamma were strongly induced by AT ODN compared to the unexposed controls, while T(H)-2 type cytokines were not induced. These results indicate that the AT ODN can augment the T(H)-1 immune response, which plays an important role in prevention of allergic responses. Moreover, the swine TLR9 transfectant demonstrated its usefulness for evaluation of immunostimulation by bacterial DNA through the detection of T(H)-1, T(H)-2 type cytokine induction via TLR9 signaling.     

Inhibition of T suppressor cell expression by histamine type 2 (H2) receptor antagonists

The effect of histamine type 2 (H2) receptor antagonists, cimetidine and ranitidine, on the induction and expression of hapten-specific suppressor T cells was studied. The activity of DNBSO3 -induced suppressor cells was evaluated after adoptive transfer to naive syngeneic recipients. Treatment with cimetidine or ranitidine markedly inhibited suppressor T cell activity in a dose-related manner and enhanced the contact sensitivity response to DNFB. Both H2 antagonists were effective in inhibiting the expression and, to a lesser extent, the induction of suppressor T cells. In contrast, norburimamide , a non-H2 antagonist structurally related to cimetidine, was inactive. The relevance of these findings to the clinical observation of cimetidine-induced reversal of acquired tolerance to dinitrochlorobenzene in anergic patients is discussed.     

Inhibition of PTPs by H(2)O(2) regulates the activation of distinct MAPK pathways

It has been shown that endogenous production of reactive oxygen species (ROS) during T cell activation regulates signaling events including MAPK activation. Protein tyrosine phosphatases (PTPs) have been regarded as targets of ROS which modify the catalytic cysteine residues of the enzymes. We have analyzed the interplay between the inhibition of PTPs and the activation of MAPK by H(2)O(2). Stimulation of Jurkat T cells with H(2)O(2) induces the phosphorylation of ERK, p38, and JNK members of MAPK family. H(2)O(2) stimulation of T cells was found to inhibit the PTP activity of CD45, SHP-1, and HePTP. Transfection of cells with wtSHP-1 decreased H(2)O(2)-induced ERK and JNK phosphorylation without affecting p38 phosphorylation. Transfection with wtHePTP inhibited H(2)O(2)-induced ERK and p38 phosphorylation without inhibiting JNK phosphorylation. The Src-family kinase inhibitor, PP2, inhibited the H(2)O(2)-induced phosphorylation of ERK, p38, and JNK. The phospholipase C (PLC) inhibitor, U73122, or the protein kinase C (PKC) inhibitor, Ro-31-8425, blocked H(2)O(2)-induced ERK phosphorylation, whereas the same treatment did not inhibit p38 or JNK phosphorylation. Taken together, these results suggest that inhibition of PTPs by H(2)O(2) contributes to the induction of distinct MAPK activation profiles via differential signaling pathways.