Daniela Tramonti

Curcumin Inhibits Activation of Vγ9Vδ2 T Cells by Phosphoantigens and Induces Apoptosis Involving Apoptosis-Inducing Factor and Large Scale DNA Fragmentation

Curcumin, in addition to its role as a spice, has been used for centuries to treat inflammatory disorders. Although the mechanism of action remains unclear, it has been shown to inhibit the activation of NF-κB and AP-1, transcription factors required for induction of many proinflammatory mediators. Due to its low toxicity it is currently under consideration as a broad anti-inflammatory, anti-tumor cell agent. In this study we investigated whether curcumin inhibited the response of γδ T cells to protease-resistant phosphorylated derivatives found in the cell wall of many pathogens. The results showed that curcumin levels ≥30 μM profoundly inhibited isopentenyl pyrophosphate-induced release of the chemokines macrophage inflammatory protein-1α and -1β and RANTES. Curcumin also blocked isopentenyl pyrophosphate-induced activation of NF-κB and AP-1. Commencing around 16 h, treatment with curcumin lead to the induction of cell death that could not be reversed by APC, IL-15, or IL-2. This cytotoxicity was associated with increased annexin V reactivity, nuclear expression of active caspase-3, cleavage of poly(ADP-ribose) polymerase, translocation of apoptosis-inducing factor to the nucleus, and morphological evidence of nuclear disintegration. However, curcumin led to only large scale DNA chromatolysis, as determined by a combination of TUNEL staining and pulse-field and agarose gel electrophoresis, suggesting a predominantly apoptosis-inducing factor-mediated cell death process. We conclude that γδ T cells activated by these ubiquitous Ags are highly sensitive to curcumin, and that this effect may contribute to the anti-inflammatory properties of this compound.

Delineation of the function of a major gamma delta T cell subset during infection.

γδ T cells play important but poorly defined roles in pathogen-induced immune responses and in preventing chronic inflammation and pathology. A major obstacle to defining their function is establishing the degree of functional redundancy and heterogeneity among γδ T cells. Using mice deficient in Vγ1+ T cells which are a major component of the γδ T cell response to microbial infection, a specific immunoregulatory role for Vγ1+ T cells in macrophage and γδ T cell homeostasis during infection has been established. By contrast, Vγ1+ T cells play no significant role in pathogen containment or eradication and cannot protect mice from immune-mediated pathology. Pathogen-elicited Vγ1+ T cells also display different functional characteristics at different stages of the host response to infection that involves unique and different populations of Vγ1+ T cells. These findings, therefore, identify distinct and nonoverlapping roles for γδ T cell subsets in infection and establish the complexity and adaptability of a single population of γδ T cells in the host response to infection that is not predetermined, but is, instead, shaped by environmental factors.

A subset of IL-10-producing gammadelta T cells protect the liver from Listeria-elicited, CD8(+) T cell-mediated injury

Although γδ T cells play a role in protecting tissues from pathogen‐elicited damage to bacterial, viral and parasitic pathogens, the mechanisms involved in the damage and in the protection have not been clearly elucidated. This has been addressed using a murine model of listeriosis, which in mice lacking γδ T cells (TCRδ–/–) is characterised by severe and extensive immune‐mediated hepatic necrosis. We show that these hepatic lesions are caused by Listeria‐elicited CD8+ T cells secreting high levels of TNF‐α that accumulate in the liver of Listeria‐infected TCRδ–/– mice. Using isolated populations of γδ T cells from wild‐type and cytokine‐deficient strains of mice to reconstitute TCRδ–/– mice, the TCR variable gene 4 (Vγ4)+ subset of γδ T cells was shown to protect against liver injury. Hepatoprotection was dependent upon their ability to produce IL‐10 after TCR‐mediated interactions with Listeria‐elicited macrophages and CD8+ T cells. IL‐10‐producing Vγ4+ T cells also contribute to controlling CD8+ T cell expansion and to regulating and reducing TNF‐α secretion by activated CD8+ T cells. This effect on TNF‐α production was directly attributed to IL‐10. These findings identify a novel mechanism by which pathogen‐elicited CD8+ T cells are regulated via interactions with, and activation of, IL‐10‐producing hepatoprotective γδ T cells.

Evidence for the opposing roles of different γδ T cell subsets in macrophage homeostasis

To ensure invading pathogens are eliminated with minimal damage to host tissues it is essential that macrophage activation be tightly regulated. Previously we demonstrated that a subset of γδ T cells (Vγ1+) contributes to resolving pathogen‐induced immune responses by killing activated macrophages. However, the exaggerated macrophage response seen in infected Vγ1+ T cell‐deficient mice suggests that γδ T cells play a broader role in macrophage homeostasis and other subsets might promote macrophage activation. Using a macrophage:γδ T cell co‐culture system we have shown that γδ T cells increase the activity of macrophages activated in vivo by Listeria monocytogenes infection. In a dose‐dependent manner, γδ T cells up‐regulated production of cytokines (TNF‐α, IL‐6, IL‐10) and chemokines (MIP‐1α, MIP‐1β) by Listeria‐elicited macrophages. The ability to increase macrophage cytokine production was prominent among Vγ4+ γδ T cells. Reciprocally, Vγ4+ γδ T cells were activated by Listeria‐elicited macrophages, resulting in production of the anti‐inflammatory cytokine, IL‐10. γδ T cell adoptive transfer experiments showed that Vγ4+ T cells protected TCRδ–/– mice against Listeria‐induced liver injury and necrosis. These findings identify distinct and non‐overlapping roles for γδ T cell subsets in regulating macrophage function during pathogen‐induced immune responses.

Evidence for a role of γδ T cells in demyelinating diseases as determined by activation states and responses to lipid antigens

Abstract In this report we review current information on the phenotypic and functional properties of γδ T cells in demyelinating disorders. The results support the conclusion that although γδ T cells show evidence of activation in patients with either multiple sclerosis (MS) or Guillain Barre syndrome (GBS), differences exist in the phenotypic and functional properties of these cells between the two diseases. In particular, our data indicate that in patients with MS the Vδ2 subset is activated and that these cells can be induced to secrete high levels of proinflammatory cytokines. In contrast, in patients with GBS, the Vδ1 subset is expanded and can be induced to secrete cytokines more associated with a humoral response.

Gangliosides act as onconeural antigens in paraneoplastic neuropathies

We describe two patients with progressive neuropathy and lung cancer in whom gangliosides (GS) may represent the oncoantigens. Patient 1 had motor neuropathy, high titers of IgG1 and IgG3 to GD1a and GM1, and expansion of circulating gamma-delta T lymphocytes, a T-cell subset responding to glycolipids. Patient 2 presented with Miller-Fisher-like syndrome and IgG3 activity to disialo-GS. In both cases, decreased autoimmune responses and stabilization of neuropathy were accomplished by tumor treatment. By immunohistochemistry, patient 1s IgG bound to his own tumor and to structures of normal nervous system expressing GD1a or GM1. Infiltration of IgG in the same neural structures was found at his autopsy. Regarding cellular immunity, the proportion of gamma-delta T lymphocytes infiltrating carcinoma from patient 1 was significantly higher than in neoplastic controls. These results indicate that GS may represent onconeural antigens in paraneoplastic neuropathy (PNN); their expression on neoplastic tissue may elicit autoimmune responses, which also target neural structures.

γδT cell‐mediated regulation of chemokine producing macrophages during Listeria monocytogenes infection‐induced inflammation

Infection of γδT cell‐deficient (TcRδ−/−) mice with the intracellular bacterium Listeria monocytogenes (Lm) results in an exacerbated inflammatory response characterized by the accumulation of activated macrophages and necrotic liver lesions. Here we investigated whether changes in chemokine production by Lm‐elicited macrophages contribute to this abnormal inflammatory response. In response to Lm infection, activated macrophages accumulate in the primary sites of infection in TcRδ−/− mice and express high amounts of mRNA encoding the chemokines CCL3 (MIP‐1α), CCL4 (MIP‐1β), CXCL2 (MIP‐2) and CXCL10 (IP‐10). In the infected tissues of TcRδ−/− the number of chemokine‐synthesizing macrophages was higher than in wild‐type (WT) mice, with the amount of MIP‐1α and MIP‐1β secreted by individual macrophages in the spleen of TcRδ−/− mice also being significantly higher than in WT mice. By contrast, protease activity and NO production in individual splenic macrophages of Lm‐infected TcRδ−/− and WT mice were comparable. Pathogen‐elicited macrophages in TcRδ−/− mice also expressed high levels of the CCL3 and CCL4 receptor, CCR5. In macrophage‐γδT cell co‐cultures, chemokine‐producing macrophages were killed by cytotoxic Vγ1+ T cells in a Fas–FasL‐dependent manner consistent with the high levels of chemokine‐producing macrophages seen in infected TcRδ−/− mice being due to the absence of Vγ1+ T cells. Together these findings highlight the importance of γδT cells in regulating macrophage anti‐microbial responses. Copyright

T cell response to N-formylated peptides in humans

We present the first evidence of a T lymphocyte response to N‐formylated peptides in humans. N‐formylated peptide sequences from self (mitochondrial) and foreign (microbial) antigens were usedto isolate antigen‐specific T cell clones from healthy individuals, including a set of monozygotic twins. The observed response differed from that previously described in mouse (CD4+ phenotype and MHC class II restriction in humans vs. CD8+ phenotype and class I restriction in mice). These lymphocytes produce substantial amounts of IFN‐γ. They were isolated in only one of the monozygotic twins, which suggests that their expansion in the healthy immune repertoire is independent of the genetic background. Our result will help in assessing the relevance of N‐formylated peptide‐specific T cells in protection against infections within the human immune system.