Search results for " T-Cell"
showing 10 items of 320 documents
Granulysin‐Dependent Killing of Intracellular and ExtracellularMycobacterium tuberculosisby Vγ9/Vδ2 T Lymphocytes
2001
Contribution of Vgamma9/Vdelta2 T lymphocytes to immune protection against Mycobacterium tuberculosis is still a matter of debate. It was reported earlier that Vgamma9/Vdelta2 T lymphocytes kill macrophages harboring live M. tuberculosis through a granule-dependent mechanism that results in killing of intracellular bacilli. This study found that Vgamma9/Vdelta2 T lymphocytes reduce the viability of both extracellular and intracellular M. tuberculosis. Granulysin and perforin, both detected in Vgamma9/Vdelta2 T lymphocytes, play a major role, which indicates that Vgamma9/Vdelta2 T lymphocytes directly contribute to a protective host response against M. tuberculosis infection.
Function of Dipeptidyl Peptidase IV (CD26, Tp103) in Transfected Human T Cells
1993
CD26 (Tp103) is a proteolytic enzyme (dipeptidyl peptidase IV) expressed on the T cell surface that defines an alternative activation signal for human T lymphocytes. It is absent from or present in only low amounts on resting T cells but it is expressed strongly after activation. Crosslinking of CD26/Tp103 via the monoclonal antibody CB.1 triggers functional activities in preactivated T cells. To study the molecular requirements for T cell activation via CD26 we transfected a cDNA encoding CD26 into several CD26-negative cells. In Jurkat T cell leukemia cells that normally do not express the CD26 antigen, the transfected CD26 molecule is functional because the monoclonal antibody CB.1 induc…
Mycobacterial antigen(s) induce anergy by altering TCR- and TCR/CD28-induced signalling events: insights into T-cell unresponsiveness in leprosy.
2009
Present study investigates the role of Mycobacterium leprae (M. leprae) antigens on TCR- and TCR/CD28-induced signalling leading to T-cell activation and further correlates these early biochemical events with T-cell anergy, as prevailed in advanced stages of leprosy. We observed that both whole cell lystae (WCL) and soluble fraction of M. leprae sonicate (MLSA) not only inhibited TCR, thapsigargin and ionomycin induced calcium fluxes by diminishing the opening of calcium channels, but also TCR- or TCR/CD28-induced proximal signalling events like phosphorylation of Zap-70 and protein kinase-C (PKC) activity. Study of TCR- and TCR/CD28-induced downstream signals revealed that M. leprae antige…
Selective depression of interferon-γ and granulysin production with increase of proliferative response by Vγ9/Vδ2 T cells in children with tuberculos…
2002
Vgamma9/Vdelta2 T cells can contribute to protective immune response against Mycobacterium tuberculosis, although the extent to which and mechanisms by which they could actually protect against human tuberculosis remain unclear. We have previously reported that Vgamma9/Vdelta2 T cells from tuberculin purified protein derivative (PPD)-positive children, either healthy or affected by different clinical forms of tuberculosis, strongly proliferate to different phosphoantigens in vitro, whereas Vgamma9/Vdelta2 T cells from PPD-negative healthy subjects proliferate very poorly. We report here that Vgamma9/Vdelta2 T cells from tuberculous children have an increased proliferative activity, but decr…
Inducible Co-Stimulator Null MRL-Fas lpr Mice
2005
MRL/MpJ-Tnfrsf6lpr (MRL-Faslpr) mice develop a spontaneous T cell-dependent autoimmune disease that shares features with human lupus, including fatal nephritis, systemic pathology, and autoantibodies (autoAb). The inducible co-stimulator (ICOS) is upregulated on activated T cells and modulates T cell-mediated responses. To investigate whether ICOS has an essential role in regulating autoimmune lupus nephritis and the systemic illness in MRL-Faslpr mice, ICOS null (-/-) MRL Faslpr and ICOS intact (+/+) MRL-Faslpr strains (wild-type [WT]) were generated and compared. It was determined that in ICOS-/- MRL-Faslpr as compared with the WT strain, (1) there is a significant reduction in circulatin…
Gamma delta T cells inhibit in vitro growth of the asexual blood stages of Plasmodium falciparum by a granule exocytosis-dependent cytotoxic pathway …
2004
Several reports have stated the ability of gamma delta T cells to inhibit the growth of the asexual blood stages of Plasmodium falciparum in vitro. However, little information is available about the mechanisms involved. In this study, in vitro systems were used to study the role of the granule exocytosis-dependent cytotoxic pathway in the growth inhibition/killing of P. falciparum by human gamma delta T cells. Our results show that the inhibition requires cell-to-cell contact and that gamma delta T cells kill the asexual blood stages of P. falciparum through a granule exocytosis-dependent cytotoxic pathway after recognition of certain ligands or molecules expressed on the surface of infecte…
An antigen-independent physiological activation pathway for L3T4+ T lymphocytes.
1987
The data presented in this report describe an antigen-independent activation pathway leading to reinduction of proliferation of class II major histocompatibility complex (MHC)-restricted murine T cell lines that after previous antigen-specific stimulation reverted to a resting state. Antigen-independent proliferation and interleukin 2 (IL2)-receptor expression occur in the presence of splenic accessory cells, exogenous IL2 and a soluble factor(s) provisionally termed T cell-stimulating factor(s) (TSF). Each of these components is essential for inducing growth. TSF is found in the supernatant of an autoreactive T cell line upon stimulation with syngeneic accessory cells. Neither TSF nor acce…
The role of ICOS in directing T cell responses: ICOS-dependent induction of T cell anergy by tolerogenic dendritic cells.
2009
Abstract Tolerogenic dendritic cells (DC) play an important role in maintaining peripheral T cell tolerance in steady-state conditions through induction of anergic, IL-10-producing T cells with suppressive properties. ICOS, an activation-induced member of the CD28 family on T cells, is involved in the induction of IL-10, which itself could contribute to induction of anergy and development of suppressive T cells. Therefore, we analyzed the functional role of ICOS in the differentiation process of human CD4+ T cells upon their interaction with tolerogenic DC. We compared the functional properties of CD4+ T cells from healthy volunteers and ICOS-deficient patients after stimulation with tolero…
Herpes virus saimiri-transformed human T lymphocytes: normal functional phenotype and preserved T cell receptor signalling
1993
Herpes virus saimiri (HVS), a primate herpes virus, transforms human CD4+ and CD8+ T lymphocytes to continuous growth in vitro. We have previously shown that HVS-transformed human T cells (HVS-T cells) respond to stimulation via CD2 with autocrine growth. In the present study we have investigated the functional characteristics of HVS-T cells. We describe that these cells can perform all the functions of normal T cells, i.e. cytokine secretion, cytotoxicity, and exocytosis of granule esterases. All these activities can be triggered via CD2 by binding to its natural ligand or via the TCR, e.g. by anti-TCR antibodies, by recognition of a bacterial superantigen and by MHC-restricted recognition…
Reduced CD4 and CD8 expression in human thymuses treated with soluble CD4.
1991
Recent data suggest that accessory molecules like CD4 and CD8 act as co-receptors in intrathymic T-cell development. Soluble CD4 (sCD4) molecules offer a novel experimental approach to investigate the relevance of CD4 interaction with its putative intrathymic receptor for T-cell maturation. We attempted to inhibit binding of surface CD4 on thymocytes to its intrathymic receptor competitively by introduction of human sCD4 into human thymus tissue cultures. Our results demonstrate that sCD4, while not affecting peripheral T-cell responses as shown in control experiments, significantly affects intrathymic development of T lymphocytes. Immature CD4CD8 double positive (DP) thymocytes responded w…