(1/5141) Reciprocal control of T helper cell and dendritic cell differentiation.

It is not known whether subsets of dendritic cells provide different cytokine microenvironments that determine the differentiation of either type-1 T helper (TH1) or TH2 cells. Human monocyte (pDC1)-derived dendritic cells (DC1) were found to induce TH1 differentiation, whereas dendritic cells (DC2) derived from CD4+CD3-CD11c- plasmacytoid cells (pDC2) induced TH2 differentiation by use of a mechanism unaffected by interleukin-4 (IL-4) or IL-12. The TH2 cytokine IL-4 enhanced DC1 maturation and killed pDC2, an effect potentiated by IL-10 but blocked by CD40 ligand and interferon-gamma. Thus, a negative feedback loop from the mature T helper cells may selectively inhibit prolonged TH1 or TH2 responses by regulating survival of the appropriate dendritic cell subset.  (+info)

(2/5141) Enhanced Th1 and dampened Th2 responses synergize to inhibit acute granulomatous and fibrotic responses in murine schistosomiasis mansoni.

In murine schistosomiasis mansoni, CD4(+) Th1 and Th2 cells participate in the ovum-induced granulomatous inflammation. Previous studies showed that the interleukin-12 (IL-12)-induced Th1 response strongly suppressed the Th2-cell-mediated pulmonary granuloma development in naive or primed mice. However, liver granulomas were only moderately suppressed in egg-vaccinated, recombinant IL-12 (rIL-12)-treated infected mice. The present study shows that repeated rIL-12 injections given during early granuloma development at 5 to 7 weeks after infection prolonged the Th1 phase and resulted in gamma interferon-mediated suppression of liver granulomas. The timing is crucial: if given at 6 to 8 weeks, during the Th2-dominated phase of florid granuloma growth, the treatment is ineffective. Daily injections of rIL-12 given between 5 and 7.5 weeks during the period of granuloma growth achieved a somewhat-stronger diminution in granuloma growth with less deposition of collagen but caused 60% mortality and liver pathology. In contrast, combined treatment with rIL-12 and anti-IL-4-anti-IL-10 monoclonal antibody (MAb) injections given during the Th2 phase strongly inhibited liver granuloma growth without mortality. The diminished inflammatory response was accompanied by less deposition of collagen in the liver. Moreover, neutralization of endogenous IL-12 by anti-IL-12 MAbs effectively decreased the early Th1 phase (between 5 and 6 weeks after infection) but not the developing Th2 phase (5 to 7 weeks) of granuloma development. These studies indicate that the granulomatous response in infected mice can be manipulated by utilizing the Th1-Th2-subset antagonism with potential salutary results in the amelioration of fibrous pathology.  (+info)

(3/5141) Interleukin-10 inhibits expression of both interferon alpha- and interferon gamma- induced genes by suppressing tyrosine phosphorylation of STAT1.

Interleukin-10 (IL-10) helps maintain polarized T-helper cells in a T-helper lymphocyte 2 (Th2) phenotype. Part of this process involves the prevention of the development of Th1 cells, which are a primary source of interferon gamma (IFNgamma), a potent activator of monocytes and an inhibitor of Th2 proliferation. Because monocytes and macrophages are important mediators of Th1-type responses, such as delayed-type hypersensitivity, we sought to determine if IL-10 could directly mediate inhibition of IFNgamma- and IFNalpha-induced gene expression in these cells. Highly purified monocytes were incubated with IL-10 for 60 to 90 minutes before the addition of IFNgamma or IFNalpha. IL-10 preincubation resulted in the inhibition of gene expression for several IFN-induced genes, such as IP-10, ISG54, and intercellular adhesion molecule-1. The reduction in gene expression resulted from the ability of IL-10 to suppress IFN-induced assembly of signal transducer and activator of transcription (STAT) factors to specific promoter motifs on IFNalpha- and IFNgamma-inducible genes. This was accomplished by preventing the IFN-induced tyrosine phosphorylation of STAT1, a component of both IFNalpha- and IFNgamma-induced DNA binding complexes. Therefore, IL-10 can directly inhibit STAT-dependent early response gene expression induced by both IFNalpha and IFNgamma in monocytes by suppressing the tyrosine phosphorylation of STAT1. This may occur through the ability of IL-10 to induce expression of the gene, suppressor of cytokine signaling 3 (SOCS3).  (+info)

(4/5141) Cytokine network and resident renal cells in glomerular diseases.

This review has highlighted the cytokine network which is involved in renal damage from an initial, even transient, stage to extensive glomerular and tubulointerstitial sclerosis. Studies of a variety of different proliferative glomerulonephritides have documented the prominent role of macrophages in infiltrating mesangium, subendothelial area and crescentic formation. Thus, they stimulate crescent glomerular cells to produce other cytokines and growth factors. The identification of other mediators, released by the monocytes in the interstitium, exemplifies the important role of these cells in progressive interstitial scarring through the release of fibrogenic cytokines. In addition, renal tubular cells have been found to produce a vast array of cytokines and growth factors which participate in the generation of renal interstitial scarring.  (+info)

(5/5141) Selective recruitment of CCR4-bearing Th2 cells toward antigen-presenting cells by the CC chemokines thymus and activation-regulated chemokine and macrophage-derived chemokine.

Helper T cells are classified into Th1 and Th2 subsets based on their profiles of cytokine production. Th1 cells are involved in cell-mediated immunity, whereas Th2 cells induce humoral responses. Selective recruitment of these two subsets depends on specific adhesion molecules and specific chemoattractants. Here, we demonstrate that the T cell-directed CC chemokine thymus and activation-regulated chemokine (TARC) was abundantly produced by monocytes treated with granulocyte macrophage colony stimulating factor (GM-CSF) or IL-3, especially in the presence of IL-4 and by dendritic cells derived from monocytes cultured with GM-CSF + IL-4. The receptor for TARC and another macrophage/dendritic cell-derived CC chemokine macrophage-derived chemokine (MDC) is CCR4, a G protein-coupled receptor. CCR4 was found to be expressed on approximately 20% of adult peripheral blood effector/memory CD4+ T cells. T cells attracted by TARC and MDC generated cell lines predominantly producing Th2-type cytokines, IL-4 and IL-5. Fractionated CCR4+ cells but not CCR4- cells also selectively gave rise to Th2-type cell lines. When naive CD4+ T cells from adult peripheral blood were polarized in vitro, Th2-type cells selectively expressed CCR4 and vigorously migrated toward TARC and MDC. Taken together, CCR4 is selectively expressed on Th2-type T cells and antigen-presenting cells may recruit Th2 cells expressing CCR4 by producing TARC and MDC in Th2-dominant conditions.  (+info)

(6/5141) Patterns of A2A extracellular adenosine receptor expression in different functional subsets of human peripheral T cells. Flow cytometry studies with anti-A2A receptor monoclonal antibodies.

Signaling through A2A adenosine receptors (A2AR) regulates T lymphocyte expansion and modulates T cell receptor (TCR)-mediated effector functions in vitro. To understand the role of A2ARs in the regulation of immune response, we investigated the expression levels of this receptor in different functional lymphocyte subsets. Monoclonal anti-A2AR antibody was used to develop a flow cytometric assay to quantify the expression A2ARs on lymphocytes. We report that detectable levels of expression of A2ARs are much higher among T cells than B cells. More CD4(+) than CD8(+) T cells express A2ARs, but activation of T cells increases A2AR expression, predominantly in CD8(+) T cells. No significant differences were found in the proportion of A2AR+ cells between CD8(low) and CD8(high) T cells or between TCR/CD3(low) and TCR/CD3(high) T cells. Studies of T helper cell subsets (TH1 and TH2) reveal that lymphokine-producing cells are much more likely to express A2ARs than are cells that do not produce lymphokines. These results suggest that A2ARs are variably expressed on T cell subsets and may regulate cytokine production in activated T lymphocytes.  (+info)

(7/5141) Effect of renal dialysis therapy modality on T cell cytokine production.

INTRODUCTION: Dialysis has been associated with acute changes in the complement activation status, granulocyte markers, macrophage function, T cell activation and the release of pro-inflammatory cytokines. The most common analysis of cytokine production in patients on dialysis has focused on the changes in monokines (particularly IL-1 and TNF alpha), however it is becoming clear that T cell cytokines play a major role in the impaired lymphocyte function of dialysis patients. METHODS: To assess the effect of dialysis modality on T cell function we analysed the ability of T cells within peripheral blood mononuclear cell populations (PBMC) to produce cytokines after mitogen (phorbol-12-myristate-13-acetate; PMA and lonomycin; I) stimulation in patients on peritoneal dialysis (PD) compared to low flux haemodialysis (HD) and normal individuals (controls). RESULTS: In control PBMC, PMA + I stimulation significantly increased the percentage of CD3+ cells expressing IL-2, IFN gamma, TNF alpha, IL-4 and IL-10, as expected. However, although mitogen stimulation significantly enhanced the percentage of the classical Th1 cytokines (IL-2, IFN gamma and TNF alpha) in the low flux HD PBMC, it had no effect on CD3+ IL-2 or CD3+ TNF alpha producing cells in the PD group. In contrast, the percentage of T cells producing Th2 cytokines (IL-4 and IL-10) could not be consistently enhanced by mitogen in either dialysis group. CONCLUSIONS: We suggest that PD alters the ability of T cells to produce cytokines, possibly by causing an 'exhaustion' of the Th1 cells, thereby preventing cells to produce cytokine on ex vivo stimulation. Furthermore, since T cells from both low flux HD and PD groups could not be induced to produce Th2 cytokines we suggest that uraemia or dialysis per se inhibits T cells from producing Th2 cytokines.  (+info)

(8/5141) Marking IL-4-producing cells by knock-in of the IL-4 gene.

IL-4 is a cytokine which can be expressed by a number of cell types including Th2 cells, mast cells and a population of CD4+ NK1.1+ NK T cells. Although phenotypic markers exist for identifying each of these cell types, there is at present no known cell surface marker common to all IL-4-producing cells. Using gene targeting in embryonic stem cells, we have modified the IL-4 locus by knock-in of a transmembrane domain to generate mice that express a membrane-bound form of IL-4 (mIL-4). Flow cytometry using an IL-4-specific mAb allowed the detection of IL-secreting Th2 cells, mast cells and NK T cells from mIL-4 mice. Furthermore, the analysis of immune responses in mIL-4 mice following immunization with anti-CD3 and anti-IgD has allowed us to identify distinct subpopulations of IL-4-producing NK T cells. Thus, the expression of IL-4 in a membrane-bound form provides a novel method for the identification and characterization of IL-4-producing cells.  (+info)