γδ T‐cell lymphomas: a homogeneous entity?

gammadelta T-cells comprise an immunologically distinct lymphoid population, characterized by specific morphological, phenotypical and functional properties. Therefore it seems reasonable to speculate that neoplasms derived from this particular T-cell subset display distinct features. Indeed, the prototype gammadelta T-cell lymphoma, hepatosplenic T-cell lymphoma constitutes a unique clinicopathological entitity which is intimately associated with a gammadelta T-cell phenotype. However, gammadelta T-cell lymphomas have also been described in other extranodal sites where, unlike reactive gammadelta T-cells and hepatosplenic gammadelta T-cell lymphomas, they display an important morphological heterogeneity. Moreover, these nonhepatosplenic gammadelta T-cell lymphomas are essentially not that different from their alphabeta T-cell receptor for antigen (TCR)-expressing counterparts and thus may be incorporated in the established T-cell lymphoma subclasses. However, subtle differences regarding their histopathological appearance as well as their biological behaviour indicate that further studies to determine the exact significance of TCR expression are required. Such inquiries may contribute to the general understanding of T-cell lymphomagenesis in general, which is still obscure.     

Human γδ T‐cell responses in infection and immunotherapy: Common mechanisms,common mediators?

Upon receiving the Nobel Prize in Physiology or Medicine in 1987, Susumu Tonegawa referred to the then recent discovery of the γδ T-cell receptor and stated that "while the function of the T cells bearing this receptor is currently unknown (…) these T cells may be involved in an entirely new aspect of immunity". [Tonegawa, S., Scand. J. Immunol. 1993. 38: 303-319]. Twenty-five years of intense research later this ambivalent view still holds true. Immunologists now appreciate that γδ T cells indeed represent a highly intriguing "new aspect of immunity" that is unique and distinct from conventional lymphocytes, yet even scientists in the field still struggle to understand the molecular basis of γδ T-cell responses, especially with respect to the enigmatic mode of antigen recognition. Here, we portray the peculiar responsiveness of human Vγ9/Vδ2 T cells to microorganisms, tumor cells and aminobisphosphonates, in an attempt to integrate the corresponding - and at times confusing - findings into a "theory of everything" that may help explain how such diverse stimuli result in similar γδ T-cell responses via the recognition of soluble low molecular weight phosphoantigens.     

Therapeutic targeting of α4‐integrins in chronic inflammatory diseases: tipping the scales of risk towards benefit?

Inhibition of leukocyte trafficking via alpha4-integrin antibody blockade has recently become a validated therapeutic approach for several inflammatory diseases, including multiple sclerosis, ulcerative colitis and Crohn's disease. In the midst of this recent success, 3 patients receiving chronic treatment with the anti-alpha4 antagonist natalizumab (Tysabri) for the treatment of multiple sclerosis or Crohn's disease, developed JC-virus related progressive multifocal leukoencephalopathy (PML). These unforeseen consequences suggest that long term blockade of alpha4-integrins might prevent trafficking of non-pathogenic lymphocytes that are essential for viral immunosurveillance. In the current issue of the European Journal of Immunology Bjursten and colleagues report that long term treatment with anti-alpha4-integrin antibodies results in exacerbation of the murine model of colitis induced by the targeted deletion of the heterotrimeric G protein subunit Galphai2. In order to properly evaluate the efficacy and safety of anti-alpha4-integrin therapy, the relationship between these observations in an immunologically altered animal model and human clinical disease needs to be carefully measured.     

The Humoral Response in TCR α–/– Mice. Can γδ‐T Cells Support the Humoral Immune Response?

An optimal humoral response requires T-cell help; however, it has been questioned if this help comes exclusively from alphabeta-T cells or whether gammadelta-T cells also contribute. We have attempted to answer this question by studying the humoral response in T-cell receptor alpha-chain knockout (alpha-/-) mice, which lack the alphabetaT cell subset. Two model antigens were used to characterize the response: the thymus-independent (TI) antigen native dextran B512 (Dx), and the thymus-dependent (TD) antigen heat shock protein (HSP65) from Mycobacterium tuberculosis. When challenged with Dx, the alpha-/- mice elicited a strong antibody response and formed rudimentary germinal centres (GCs), a T-cell dependent reaction. In contrast, the humoral response to HSP65 was poor. However, alpha-/- mice became primed when challenged with HSP65, because when supplemented with wild-type thymocytes, the antigen-primed animals were able to mount a stronger response than the nonprimed ones when challenged with HSP65. A crucial step seems to be the collaboration between gammadeltaT cells and antigen presenting cells (APCs), as splenocytes from alpha-/- mice were able to respond to HSP65 in an environment containing primed-APCs. Based on these results, we propose a model for B-cell activation in the alpha-/- mice.     

ICAM‐1 and β3 integrin immunoexpression in malignant melanoma cells: can they be used as additional predictors?

Malignant melanoma usually progresses from the intraepidermal microenvironment through a distinct radial growth phase, in which malignant potential cannot always be accurately evaluated, to invasion of the dermis (vertical growth phase) and metastasis. During these stages malignant cells interact with each other and with the extracellular matrix. This interaction is mediated by cell surface adhesion molecules such as the beta(3) integrin subunit and ICAM-1. Our aim was to investigate whether the expression of these two molecules is associated with the various histopathologic prognosticators commonly evaluated in malignant melanoma. Using a standard three-step immunoperoxidase technique we evaluated the above molecules' expression in a documented series of 66 cutaneous malignant melanomas. Forty-five were superficial spreading melanomas, including 18 in mixed growth phase. Positive immunoreaction was estimated by image analysis. ICAM-1 immunopositivity status was significantly more frequent among malignant melanomas of the nodular type (p=0.0001), and was associated with the vertical growth phase, Breslow thickness of >0.77 mm, and with evident lymphocytic infiltration. beta(3) integrin immunopositivity showed similar results in certain respects; it was more frequently detected in superficial spreading melanomas in which vertical growth had developed (p=0.002) and in cases with regression. There appears to be an association of these molecules with histopathologic features that predict increased tumorigenicity of malignant melanocytes.     

The Multifunctionality of Human Vγ9Vδ2 γδ T Cells: Clonal Plasticity or Distinct Subsets?

The dominant subset of γδ T cells in human peripheral blood expresses Vγ9 paired with Vδ2 as variable TCR elements. Vγ9Vδ2 T cells recognize pyrophosphates derived from the microbial non‐mevalonate isoprenoid biosynthesis pathway at pico‐ to nanomolar concentrations. Structurally related pyrophosphates are generated in eukaryotic cells through the mevalonate pathway involved in protein prenylation and cholesterol synthesis. However, micromolar concentrations of endogenous pyrophosphates are required to be recognized by Vγ9Vδ2 T cells. Such concentrations are not produced by normal cells but can accumulate upon cellular stress and transformation. Therefore, many tumour cells are susceptible to γδ T cell–mediated lysis owing to the overproduction of endogenous pyrophosphates. This explains why Vγ9Vδ2 T cells contribute to both anti‐infective and anti‐tumour immunity. Ex vivo analysed Vγ9Vδ2 T cells can be subdivided on the basis of additional surface markers, including chemokine receptors and markers for naïve and memory T cells. At the functional level, Vγ9Vδ2 T cells produce a broad range of cytokines, display potent cytotoxic activity, regulate αβ T cell responses, and – quite surprisingly – can act as professional antigen‐presenting cells. Thus, an exceptional range of effector functions has been assigned to a population of T cells, which all recognize invariant exogenous or endogenous pyrophosphates that are not seen by any other immune cell. Here, we discuss whether this plethora of effector functions reflects the plasticity of individual Vγ9Vδ2 T cells or can be assigned to distinct subsets.     

Autoimmune diseases in vitiligo: do anti‐nuclear antibodies decrease thyroid volume?

An increased prevalence of autoimmune thyroiditis (AT) in vitiligo patients is well known. The aim of this study was firstly, to evaluate the clinical course of patients with both vitiligo and AT and secondly, to identify additional autoimmune disorders affecting the thyroid gland in a large cohort of vitiligo patients. We analysed a study group of 106 vitiligo patients and 38 controls. A detailed thyroid examination including sonography was performed in all study participants. In addition, the study participants were HLA typed and screened for various autoimmune disorders. AT was significantly more frequent in vitiligo patients than in controls (21%versus 3%; P < 0.01). In 12 of the 22 patients with AT, vitiligo was the initial disease preceding AT by 4-35 years. In the other 10 patients with AT, both vitiligo and AT were diagnosed within one year. There were two individuals with diabetes mellitus type 1 and a single patient with Addison's disease. Anti-nuclear antibody (ANA), anti-smooth muscle cell antibody, and parietal cell antibody levels occurred with a similar frequency in patients and controls. In all vitiligo patients with both elevated ANA levels and AT (n = 6), the atrophic but not the goitrous variant was diagnosed. These vitiligo patients with both AT and elevated ANA levels had a significantly smaller thyroid volume compared to the vitiligo patients with AT whose ANA levels were normal (6.7 +/- 4.5 ml versus 13.4 +/- 9.1 ml, respectively; P < 0.05). The same was found in the entire study group: Thyroid volume of all vitiligo patients (with or without concomitant AT) was significantly smaller in the presence of ANA (6.9 +/- 5.3 versus 10.5 +/- 5.9 ml, respectively; P < 0.05). However, this phenomenon was not observed in the control group. There was a trend for a decreased frequency of HLA-DR3 (6.7%versus 23%) in our study group, but after correction for the number of comparisons, no HLA-allele was statistically significant associated neither with vitiligo nor with multiple autoimmune diseases in our patient sample. Our findings suggest that AT is the most frequent autoimmune disease associated with vitiligo. In our patients, AT presented simultaneously or after the onset of vitiligo but not before. Elevated ANA levels were associated with the atrophic variant of AT and may affect the volume of the thyroid gland, and there was no statistically significant association with the HLA system.     

Can interferon‐γ and interleukin‐10 balance be associated with severity of human Leishmania (Viannia) braziliensis infection?

Suitable levels of interferon (IFN)-gamma and interleukin (IL)-10 seem to favour the outcome of cutaneous leishmaniasis (CL), while high IFN-gamma and low IL-10 production are associated with severity of mucosal leishmaniasis (ML). Considering that cytokine balance is important for the maintenance of protective responses in leishmaniasis, our aim was to investigate leishmanial antigens-induced IFN-gamma and IL-10 levels maintained in healed individuals who had different clinical outcomes of Leishmania infection. Thirty-three individuals who recovered from L. braziliensis infection were studied: cured CL (CCL), cured ML (CML), spontaneous healing of CL (SH) or asymptomatic individuals (ASY). Cytokines were quantified by enzyme-linked immunosorbent assay (ELISA) in culture supernatants of L. braziliensis-stimulated peripheral blood mononuclear cells (PBMC). IFN-gamma levels were higher in CML (7593 +/- 5994 pg/ml) in comparison to SH (3163 +/- 1526 pg/ml), ASY (1313 +/- 1048 pg/ml) or CCL (1897 +/- 2087 pg/ml). Moreover, cured ML cases maintained significantly lower production of IL-10 (127 +/- 57.8 pg/ml) in comparison to SH (1373 +/- 244 pg/ml), ASY (734 +/- 233 pg/ml) or CCL (542 +/- 375 pg/ml). Thus, a high IFN-gamma/IL-10 ratio observed in CML can indicate unfavourable cytokine balance. On the other hand, no significant difference in the IFN-gamma/IL-10 ratio was observed when CCL individuals were compared to SH or ASY subjects. In conclusion, even after clinical healing, ML patients maintained a high IFN-gamma/IL-10 secretion profile in response to leishmanial antigens. This finding can explain a delayed down-modulation of exacerbated inflammatory responses, which can be related in turn to the necessity of prolonged therapy in ML management. Conversely, lower IFN-gamma/IL-10 balance observed in CCL, SH and ASY individuals can represent a better-modulated immune response associated with a favourable prognosis.     

MR1‐restricted Vα19i T cells – a second population recognizing lipid antigens?

There is increasing evidence that T cells recognizing lipid antigens contribute to the immunological regulation of different disease conditions including autoimmunity. The best-known subset is CD1d-restricted lipid-reactive T cells characterized by the expression of an invariant TCRalpha chain. Much less is known about the biology of another invariant T cell subset, which is restricted to the MHC class I-like molecule MR1. A beneficial role of MR1-restricted T cells has been suggested in a mouse EAE model. However, the nature of antigens that can be presented by MR1 to this invariant T cell subset remained largely unclear. An article in this issue of the European Journal of Immunology presents strong indications that derivatives of alpha-mannosyl ceramide (alpha-ManCer), i.e. glycolipids, can serve as ligands for MR1-restricted invariant T cells. In addition to that, the structure of the alpha-ManCer sphingosine chain influences the Th1-Th2 polarization of the cytokine response. These important new findings will foster further research on the identity of physiological ligands for MR1-restricted T cells and on their relation with immunoregulation. See accompanying article: (http://dx.doi.org/10.1002/eji.200636689).     

Transforming growth factor‐β1 in asthmatic airway smooth muscle enlargement: is fibroblast growth factor‐2 required?

Enlargement of airway smooth muscle (ASM) tissue around the bronchi/bronchioles is a histopathological signature of asthmatic airway remodelling and has been suggested to play a critical role in the increased lung resistance and airway hyperresponsiveness seen in asthmatic patients. The pleiotropic cytokine, TGF‐β1, is believed to contribute to several aspects of asthmatic airway remodelling and is known to influence the growth of many cell types. Increased TGF‐β1 expression/signalling and ASM growth have been shown to occur concurrently in animal models of asthma. Abundant studies further substantiate this association by showing that therapeutic strategies that reduce or prevent TGF‐β1 overexpression/signalling lead to a parallel decrease or prevention of ASM enlargement. Finally, recent findings have supported a direct link of causality between TGF‐β1 overexpression/signalling and the overgrowth of ASM tissue. To follow‐up on these in vivo studies, many investigators have pursued detailed investigation of ASM in cell culture conditions, assessing the direct role of TGF‐β1 on cellular proliferation and/or hypertrophy. Inconsistencies among the in vitro studies suggest that the effect of TGF‐β1 on ASM cell proliferation/hypertrophy is contextual. A hypothesis focusing on fibroblast growth factor‐2 is presented at the end of this review, which could potentially reconcile the apparent discrepancy between the conflicting in vitro findings with the consistent in vivo finding that TGF‐β1 is required for ASM enlargement in asthma. Cite this as: Y. Bossé, J. Stankova and M. Rola‐Pleszczynski, Clinical & Experimental Allergy, 2010 (40) 710–724.     

Synthesis of Novel Monomers and Copolymers from 1‐Vinylpyrrolidin‐2‐one: Attractive Materials for Drug Delivery Systems?

Summary: Polyvinylpyrrolidone (PVP) is a synthetic, non‐toxic, water‐soluble polymer commonly used in a wide range of applications including several pharmaceutical applications. One example of an important application is the controlled release and delivery of therapeutic agents into sites of inflammation or tumours. However, PVP lacks reactive groups, which limits the possibility of adding new functions to the polymer in order to modify its physical and chemical properties. Furthermore, large differences in radical reactivity between 1‐vinylpyrrolidin‐2‐one (NVP) and most other monomers lead to compositional drift during copolymerization. This complicates the introduction of reactive groups into the polymer using this method. Monomers that are derivatives of NVP itself are expected to show smaller differences in radical reactivity and therefore provide a way of preparing PVP with adjustable properties. Here we present the synthesis of five NVP‐based monomers and their use in the preparation of functional PVP with adjustable properties in terms of solubility, loading of functional groups, and molar mass. The results show the possibility of tailoring PVP for different biomedical applications e.g. drug delivery systems.

Copolymers from 1‐vinylpyrrolidin‐2‐one.     

Are alterations of lymphocyte subpopulations in polymicrobial sepsis and DHEA treatment mediated by the tumour necrosis factor (TNF)‐α receptor (TNF‐RI)? A study in TNF‐RI (TNF‐RI–/–) knock‐out rodents

Sepsis is associated with depression of T cell-dependent immune reactivity with proinflammatory cytokines, such as tumour necrosis factor (TNF)-alpha, playing an important role. Recent investigations describe an association between these immunological alterations and disturbances of the endocrine system, related most frequently to sex steroid hormones. Dehydroepiandrosterone (DHEA), one of the most abundant adrenal sex steroid precursors, seems to have a protective immunological effect towards septic insults. In this study, both the role of TNF-receptor I (RI) and possible interactions in the protective role of DHEA were investigated in a murine model of polymicrobial sepsis. Polymicrobial sepsis was induced by caecal ligation and puncture (CLP) in a murine model. The effects of DHEA on survival, clinical parameters and cellular immunity (T lymphocytes and natural killer (NK) cells) were investigated. CLP was performed in genetically modified TNF-RI knock-out (TNF-RI(-/-)) and genetically unmodified (wild-type, WT) mice. DHEA application was associated with a decrease in the mortality rate in WT animals. A mortality rate of 91.7% was observed in TNF-RI(-/-) mice after CLP. This mortality rate was reduced to 37.5% by the application of DHEA. In sham-operated TNF-RI(-/-) animals, a significantly higher proportion of NK cells within the lymphocyte population was measured compared with the corresponding WT group. After CLP, a significant increase in the percentage cell count of NK cells was recorded in WT mice. Overall, following DHEA application in WT mice, an alteration in the cellular immune response was characterized by a reduction in the percentage counts of CD4(+), CD8(+) and NK cells. In the group of TNF-RI(-/-) mice treated with DHEA, no increase in the percentage cell count of NK cells was observed after CLP. No data for cell analysis were available from the CLP-TNF-RI(-/-) mice treated with saline, due to the high mortality rate in these animals. DHEA reduces the complications of sepsis in a TNF-RI-independent manner. Our study suggests that NK cells are involved in the protective mechanism of DHEA in WT mice. It would therefore seem that DHEA represents a feasible alternative therapy for the dysregulated immune system in sepsis.