How do cytotoxic lymphocytes kill their targets?

Intraduodenal priming of mice with reovirus serotype 1/strain Lang (reovirus 1/L) stimulates gut lymphocytes and generates precursor and effector CTLs. Our earlier studies demonstrated that germinal center and T cell Ag (GCT) is a marker which identifies reovirus 1/L-specific precursor CTL and effector CTL in Peyer’s patches (PP) of reovirus 1/L-inoculated mice. In this study, we characterized the expression of the activation markers, GCT and CD11c, on reovirus 1/L-stimulated gut lymphocytes and the effector mechanisms involved in reovirus 1/L-specific cytotoxicity. We found that intraduodenal reovirus 1/L inoculation of mice induced the expression of both GCT and CD11c on PP lymphocytes (PPL), intraepithelial lymphocytes (IEL), and lamina propria lymphocytes (LPL), and these activated cells expressed Fas ligand (FasL). The majority of the GCT+CD11c+ IEL and LPL expressed a phenotype, TCRαβ+Thy-1+CD8+ similar to that expressed on reovirus 1/L-stimulated PPL. However, splenic lymphocytes expressed GCT but not CD11c after stimulation with reovirus 1/L. Perforin, Fas-FasL, and TRAIL pathways were found to be involved in PPL, IEL, and LPL cytotoxic activity against reovirus 1/L-infected targets. In PPL, perforin and Fas-FasL pathways were more effective than TRAIL. In IEL, all three cytotoxic mechanisms were equally as effective. However, LPL prefer Fas-FasL and TRAIL over perforin. Further, we demonstrated the preferential migration of GCT+ PPL to the intraepithelial compartment and the lamina propria. These results suggest that GCT and CD11c can be used as activation markers for gut lymphocytes and CD11c can also be used to differentiate between activated gut and systemic lymphocytes.

Section: Discussionmentioning

confidence: 99%

“…The second pathway is mediated by T cell Fas ligand (FasL) engagement of Fas expressed by target cells. Use of the Fas-FasL pathway of target cell lysis is thought to be favored by CD4 ϩ T cells (16). However, human virus-specific CD4 ϩ T cells can also use the perforin/granzyme pathway of cytotoxicity (17).…”

mentioning

confidence: 99%

Reovirus Serotype 1/Strain Lang-Stimulated Activation of Antigen-Specific T Lymphocytes in Peyer’s Patches and Distal Gut-Mucosal Sites: Activation Status and Cytotoxic Mechanisms

Bharhani

Grewal

Pilgrim

et al. 2005

“…These effector functions include secretion of cytokines, such as IFN-␥ and TNF-␣, as well as cytolytic activity mediated by perforin and granzyme B (3)(4)(5). Because HBV does not infect mice, an HBV transgenic mouse model was developed to enable the study of HBV-specific CTL effector functions in vivo (6).…”

Section: Pd-1:pd-l1 Interactionsmentioning

confidence: 99%

PD-1:PD-L1 Interactions Contribute to the Functional Suppression of Virus-Specific CD8+ T Lymphocytes in the Liver

Maier

Isogawa

Freeman

et al. 2007

215

172

Mechanisms contributing to the development of chronic viral infections, including chronic hepatitis B virus (HBV) infections, are not well understood. We have shown recently that production of IFN-γ, an important antiviral cytokine, by HBV-specific CTLs is rapidly induced when they enter the liver of HBV transgenic mice, and then rapidly suppressed, despite the continued presence of Ag. Suppression of IFN-γ production by the CTLs coincides with the up-regulation of programmed cell death (PD)-1, a cell surface signaling molecule known to inhibit T cell function. To determine whether PD-1 plays a role in the functional suppression of IFN-γ secretion by CTLs, we treated HBV transgenic mice with blocking Abs specific for PD ligand (PD-L)1, the most widely expressed PD-1 ligand, and adoptively transferred HBV-specific CTLs. Treatment with anti-PD-L1 Abs resulted in a delay in the suppression of IFN-γ-producing CTLs and a concomitant increase in the absolute number of IFN-γ-producing CTLs in the liver. These results indicate that PD-1:PD-L1 interactions contribute to the suppression of IFN-γ secretion observed following Ag recognition in the liver. Blockade of inhibitory pathways such as PD-1:PD-L1 may reverse viral persistence and chronic infection in cases in which the CTL response is suppressed by this mechanism.

“…Studies with in vitro expanded T cell clones and experiments in mutant mice have provided evidence that CTL can exert their effector functions by at least two independent pathways: granule exocytosis and the Fas/FasL pathway (19). The granule exocytosis pathway involves secretion of granules containing cytotoxic effector molecules onto the surface of target cells.…”

Section: Cytolytic Mechanisms and Expression Of Activation-regulatingmentioning

confidence: 99%

Cytolytic Mechanisms and Expression of Activation-Regulating Receptors on Effector-Type CD8+CD45RA+CD27− Human T Cells

Baars

Couto

Leusen

et al. 2000

Circulating CD8+ T cells with a CD45RA+CD27− phenotype resemble cytolytic effector cells because they express various cytolytic mediators and are able to execute cytotoxicity without prior stimulation in vitro. We here demonstrate that CD8+CD45RA+CD27− T cells can use both granule exocytosis and Fas/Fas ligand pathways to induce apoptosis in target cells. The availability of these cytolytic mechanisms in circulating T cells suggests that the activity of these cells must be carefully controlled to prevent unwanted tissue damage. For this reason, we analyzed the expression of surface receptors that either enhance or inhibit T cell function. Compared with memory-type cells, effector cells were found to express normal levels of CD3ε and TCRζ and relatively high levels of CD8. CTLA-4 was absent from freshly isolated effector cells, whereas a limited number of unstimulated memory cells expressed this molecule. In line with recent findings on CD8+CD28− T cells, CD45RA+CD27− T cells were unique in the abundant expression of NK cell-inhibitory receptors, both of Ig superfamily and C-type lectin classes. Binding of NK cell-inhibitory receptors to classical and nonclassical MHC class I molecules may inhibit the activation of the cytolytic machinery induced by either Ag receptor-specific or nonspecific signals in CD8+CD45RA+CD27− T cells.