VIP and PACAP inhibit Fas ligand-mediated bystander lysis by CD4+ T cells
Introduction
Two independent lytic pathways mediate T-cell cytotoxicity (Berke, 1995, Nagata and Golstein, 1995): a calcium-dependent degranulation pathway, in which exocytosis of perforin in combination with granzymes results in lysis of target cells (Shiver et al., 1992), and a calcium-independent pathway, which involves interactions between Fas ligand (FasL) expressed on cytotoxic T cells (CTLs) and the Fas protein present on target cells (Rouvier et al., 1993, Kagi et al., 1994, Walsh et al., 1994, Takahashi et al., 1994). Fas-mediated lysis is controlled mainly through the regulation of FasL expression. FasL expression and subsequent Fas-mediated cytotoxicity are induced following treatment of T cells with a variety of stimuli, including appropriate Ag–MHC complexes, TCR cross-linking with anti-CD3 Ab, and pharmacological agents that mimic TCR activation, such as phorbol esters plus calcium ionophores (Rouvier et al., 1993, Ju et al., 1994, Stalder et al., 1994). The perforin/granzyme pathway plays a major role in the elimination of virally-infected cells or allogeneic grafts, whereas Fas-mediated cytotoxicity appears to be the major player in immune homeostasis and tolerance induction (Vignaux and Golstein, 1994, Bellgrau et al., 1995).
CD8+ T cells using the perforin/granzyme pathway are the classical effectors in response to viral antigens. However, Th1 CD4+ T cells display cytolytic activity through the FasL/Fas pathway, lysing activated APCs (direct targets), and neighboring bystanders (Fas-expressing non-APCs) (Erb et al., 1990, Lancki et al., 1991, Ju, 1991, Lowin et al., 1994, Kojima et al., 1994, Ju et al., 1994, Stalder et al., 1994). The APC activates the CD4+ T cell in a MHC II-restricted manner, leading to the up-regulation of FasL, which then enables the CD4+ T cell to lyse Fas-bearing targets found in the vicinity, in a MHC-nonrestricted and Ag-nonspecific manner. In vitro, bystander lysis by CD4+ T cells requires the simultaneous presence of the CD4+ cytotoxic T cells, the cognate APC, and the bystander (Wang et al., 1996, Smyth, 1997).
Although Fas-mediated cytotoxicity plays an important role in maintaining T cell homeostasis, the Fas-mediated lysis of bystander targets has been implicated in the pathogenesis of several autoimmune and inflammatory diseases, especially in tissues with limited or restricted MHC II expression (reviewed in De Maria and Testi, 1998). The mechanisms limiting the killing of innocent bystanders are not understood, and the identification of factors that regulate this process represents the focus of considerable research.
Vasoactive intestinal peptide (VIP), and the structurally related peptide, the pituitary adenylate cyclase-activating polypeptide (PACAP), are two neuropeptides released in the immune microenvironment (Leceta et al., 1996, Bellinger et al., 1996), affecting both natural and acquired immunity, predominantly as anti-inflammatory agents (Ganea, 1996, Delgado et al., 1999a, Pozo et al., 2000). Recently we reported that VIP and PACAP inhibit activation-induced FasL expression and subsequent cell death in T cells and T cell hybridomas (Delgado and Ganea, 2000a), as well as the FasL-mediated cytotoxic activity of alloreactive CD8+ CTLs (Delgado and Ganea, 2000b). In this study, we investigate the effects of VIP and PACAP on FasL/Fas-mediated cytotoxicity of in vivo primed effector CD4+ T cells against direct and bystander targets. Our studies indicate that VIP/PACAP inhibit both the direct and bystander lysis of syngeneic targets by CD4+ T cells, through the down-regulation of FasL expression on the cytotoxic effectors.
Section snippets
Reagents
Synthetic VIP, PACAP38, and keyhole limpet hemocyanin (KLH) were purchased from Calbiochem (San Diego, CA). Monoclonal Abs to murine FasL (CD95L, clone MFL3), Fas (CD95, clone Jo2), CD4, CD8 (clone 53-6.7), and CD3ϵ (clone 2C11) were purchased from Pharmingen (San Diego, CA). Ovalbumin (OVA), PMA and ionomycin were purchased from Sigma Chemicals Co. (St. Louis, MO).
Mice, cell lines and cell culture
Female 6- to 8-week-old BALB/c (H-2d) and C57BL/6 (H-2b) mice were purchased from Jackson Laboratory (Bar Harbor, ME).
The Iad
VIP and PACAP inhibit the FasL/Fas-mediated cytotoxicity of allogeneic CTLs generated in vivo
We have previously shown that VIP and PACAP inhibit FasL/Fas-mediated, but not the perforin/granzyme-mediated cytotoxicity of in vitro generated CTLs against allogeneic targets (Delgado and Ganea, 2000b). Here, we generated allogeneic Balb/c anti-H-2b effector CTL in vivo in response to C57Bl/6 spleen cells. The effector CTL harvested from lymph nodes were activated in vitro with immobilized anti-CD3 Abs in the presence or absence of VIP or PACAP, and the cytotoxic activity against both
Discussion
FasL/Fas-mediated cytotoxicity plays a major role in the homeostasis of the immune system. Apoptosis of CD4+ T cells during activation-induced cell death, which reduces the numbers of antigen-activated T cells following an immune response, and the killing of activated antigen-presenting cells by CD4+ lytic effectors occur through FasL/Fas interactions (Ju et al., 1994, Ju et al., 1995, Stalder et al., 1994). In contrast, although Fas-mediated lysis operates in the elimination of
Acknowledgements
We thank Dr. Pierre Golstein (Centre d’Immunologie INSERM-CNRS, Marseille, France) for L1210 and L1210-Fas+ cells.
This work was supported by grants PHS AI 041786-01 (DG), and Busch Biomedical Award 98-00 (DG), by grant PM98-0081 (MD), and by the postdoctoral fellowship from the Spanish Department of Education and Science (MD).
References (37)
- et al.
The significance of vasoactive intestinal peptide (VIP) in immunomodulation
Adv. Neuroimmunol.
(1996) The CTL kiss of death
Cell
(1995)- et al.
Fas-FasL interactions: a common pathogenetic mechanism in organ-specific autoimmunity
Immunol. Today
(1998) Regulatory effects of vasoactive intestinal peptide on cytokine production in central and peripheral lymphoid organs
Adv. Neuroimmunol.
(1996)- et al.
Two distinct pathways of specific killing revealed by perforin mutant cytotoxic T lymphocytes
Immunity
(1994) - et al.
Expression of vasoactive intestinal peptide in lymphocytes: a possible endogenous role in the regulation of the immune response
Adv. Neuroimmunol.
(1996) - et al.
Cytotoxicity with target DNA breakdown by rat basophilic leukemia cells expressing both cytolysin and granzyme A
Cell
(1992) - et al.
Molecular cloning an expression of the Fas ligand, a novel member of the tumor necrosis factor family
Cell
(1993) - et al.
Generalized lymphoproliferative disease in mice caused by a point mutation in the Fas ligand
Cell
(1994) - et al.
A role for CD95 ligand in preventing graft rejection
Nature
(1995)
Vasoactive intestinal peptide (VIP) and pituitary adenylate cyclase-activating polypeptide (PACAP38) modulate cytokine and nitric oxide production in peritoneal macrophages and macrophage cell lines
Ann. NY Acad. Sci.
VIP and PACAP differentially regulate the costimulatory activity of resting and activated macrophages through the modulation of B7.1 and B7.2 expression
J. Immunol.
VIP and PACAP inhibit antigen-induced apoptosis of mature T lymphocytes by inhibiting Fas ligand expression
J. Immunol.
VIP and PACAP inhibit T-cell mediated cytotoxicity by inhibiting FasL expression
J. Immunol.
CD4+ T cell-mediated killing of MHC class II-positive antigen-presenting cells. Characterization of target cell recognition by in vivo or in vitro activated CD4+ killer T cells
J. Immunol.
Bystander target cell lysis and cytokine production by Dengue virus-specific human CD4+ cytotoxic T lymphocyte clones
J. Virol.
Regulation of the Fas lytic pathway in cloned CTL
J. Immunol.
Mechanism and biological significance of CD4-mediated cytotoxicity
Immunol. Rev.
Cited by (10)
Correlation of Circulating T Lymphocytes and Intracranial Hypertension in Intracerebral Hemorrhage
2017, World NeurosurgeryCitation Excerpt :In this study, an increase in circulating CD4+ T lymphocytes along with a sharp increase in ICP were observed as early as 4 hours after ICH. CD4+ T lymphocytes are helper T cells that play a key role in enhancing the cellular immune response through the secretion of cytokines and chemokines.22 CD4+ T cells secret inflammatory factors to cause breakdown of the blood-brain barrier, aggravating the edema related to the brain damage in ICH.23,24
Vasoactive intestinal peptide: An anti-inflammatory neuropeptide
2007, Psychoneuroimmunology, Two-Volume SetVasoactive Intestinal Peptide: An Anti-Inflammatory Neuropeptide
2006, PsychoneuroimmunologyThe effects of PACAP on CD4 <sup>+</sup>/CD8 <sup>+</sup> T cells in rats with traumatic brain injury
2012, Chinese Journal of Emergency MedicineTherapeutical approaches of vasoactive intestinal peptide as a pleiotropic immunomodulator
2007, Current Pharmaceutical Design