Role of cytokines in the differentiation of CD4+ T-cell subsets in vivo

Host-Directed Therapies for Cutaneous Leishmaniasis

Cutaneous leishmaniasis exhibits a wide spectrum of clinical presentations from self-resolving infections to severe chronic disease. Anti-parasitic drugs are often ineffective in the most severe forms of the disease, and in some cases the magnitude of the disease can result from an uncontrolled inflammatory response rather than unrestrained parasite replication. In these patients, host-directed therapies offer a novel approach to improve clinical outcome. Importantly, there are many anti-inflammatory drugs with known safety and efficacy profiles that are currently used for other inflammatory diseases and are readily available to be used for leishmaniasis. However, since leishmaniasis consists of a wide range of clinical entities, mediated by a diverse group of leishmanial species, host-directed therapies will need to be tailored for specific types of leishmaniasis. There is now substantial evidence that host-directed therapies are likely to be beneficial beyond autoimmune diseases and cancer and thus should be an important component in the armamentarium to modulate the severity of cutaneous leishmaniasis.

Lactococcus lactis harbouring Ara h 2.02 alleviates allergen-specific Th2-associated responses in sensitized mice

AIM

To study the prophylactic effect of recombinant Lactococcus lactis (rLl) harbouring Ara h 2.02 peanut allergen, in sensitized and challenged mice.

METHODS AND RESULTS

Ara h 2.02 cDNA was cloned into pNZ8048 for heterologous expression in L. lactis. The purified recombinant allergen showed IgE binding comparable with native Ara h 2. Balb/c mice were fed with either recombinant (rLl), nonrecombinant L. lactis (Ll) or NaHCO₃ (Sham) prior to sensitization and challenged with rAra h 2.02, whereas the baseline group was only fed with Ll. Allergen-specific immunoglobulin and splenocyte cytokines responses were determined for each mouse. Mice fed with either Ll or rLl showed significant alleviation of IgE and IgG₁ compared to the Sham group. Despite no significant decrease in Th2 (IL-4, IL-13, IL-6) or increase in Th1 (IFN-γ) cytokines, both groups showed lower IL-10 level, while the IL-4 : IFN-γ ratio was significantly lower for rLl compared to Ll group.

CONCLUSIONS

Oral administration of rLl harbouring Ara h 2.02 demonstrated alleviation of Th2-associated responses in allergen-challenged mice and a possible added allergen-specific prophylactic effect.

SIGNIFICANCE AND IMPACT OF THE STUDY

Ara h 2.02 coupled with the intrinsic properties of probiotic L. lactis as a delivery vehicle can be explored for the development of a commercially scalable vaccine.

Altered Cytokine Production in Mice Exposed to Lead Acetate

Previous investigations have shown that Pb exerts immunotoxic effects. Object of this study were Th1 and Th2-type immune responses of mice to Pb exposure. Adult Swiss male mice were administered 0, 40 and 400 mg/1 of Pb (as acetate) in drinking water for 14 days . At the end of the treatment, blood Pb was determined and two Th1 cytokines (IL-2, INF-γ) and one Th2 serum cytokine (IL-4) were measured. A significant increase in IL-4 production was observed in the mice exposed to 40 mg/1 of Pb, while a further increase in IL-4 production was associated with a decrease in IFN-γ production in mice exposed to 400 mg/1 of Pb. On the other hand, Pb exposure did not induce changes of serum IL-2 (involved also in the ThO immune pattern). Our findings indicate that low level Pb exposure enhances a Th2 response. A high Pb dose can either stimulate the Th2 immune activity or reduce the Th1 response; the result is an imbalance between Th1 and Th2 activation.

Immunological Events during the Early Phase of Infection with Schistosoma Mansoni in Mice

Naturally occurring infection in humans or experimental infection in mice by Schistosoma mansoni lead to a Th1 towards Th2 switch of cytokine response in the chronic late phase of the disease. It has been proposed that an initial Th1 response is successively down-regulated and followed by an egg-antigen driven Th2 response. Here we report the results of a kinetic study on the capacity of spleen cells from experimentally infected Balb/c mice to produce Th1 or Th2 cytokines, following mitogen stimulation, during the phase which precedes the granulomatous response associated to egg-deposition. The main results were identified as an early increase in IL-4 and IL-10 Th2 cytokine production, particularly pronounced for IL-10, only a slight and delayed decrease in IL-2 production and an invariable or actually enhanced capacity to produce IFN-γ. The emergence of Th2 response was associated with only slight and delayed modifications in spleen lymphocyte subsets, mainly represented by a decrease in CD3+ T cells and an increase in B cells. The initial unbalance of the Th1/Th2 response precedes thus the egg-deposition and the chronic phase of the infection, being evident 3 weeks after the challenge with the parasite. This observation could represent a novel finding useful in understanding the complex mechanisms involved in the immunopathogenesis of schistosomiasis.

Psychoneuroimmunology: Then and Now

Psychoneuroimmunology (PNI) emerged in the neurosciences in the late 1970s to early 1980s and has extended to influence the fields of psychology, psychiatry, endocrinology, physiology, and the biomedical research community. This review documents the journey of PNI from the early 1980s to the present. Today, we recognize that the highly complex immune system interacts with an equally complex nervous system in a bidirectional manner. Evolutionarily old signals continue to play a role in these communications, as do mechanisms for protection of the host. The disparity between physical and psychological stressors is only an illusion. Host defense mechanisms respond in adaptive and meaningful ways to both. The present review will describe a new way of thinking about evolutionarily old molecules, heat shock proteins, adding to a body of evidence suggesting that activation of the acute stress response is a double-edged sword that can both benefit and derail optimal immunity.

Serum 25-hydroxyvitamin D predict prognosis in radioiodine therapy of Graves' disease

PURPOSE

To investigate serum 25-hydroxyvitamin D 25(OH)D status and assess the predictability of outcome in patients with Graves' disease (GD) who received a patient-specific calculated dose of radioiodine therapy (RIT).

METHODS

128 patients with GD who received RIT from July 2010 to September 2010 were included. Pre-therapy serum levels of 25(OH)D, calcium, phosphorus, parathyroid hormone, free triiodothyronine, free thyroxine, thyroid stimulating hormone and creatinine were measured. 60 age- and BMI-matched healthy subjects were chosen as the normal control group.

RESULTS

Post-therapy follow-up results revealed that therapy failed in 25.00 % of the patients. Serum 25(OH)D levels were found to be significantly lower in patients who failed in therapy. The prevalence of vitamin D deficiency in GD patients was significantly higher compared with control subjects (56.25 vs. 10.00 %, P < 0.001), and therapy failed in 27 (37.50 %) of these patients whose serum 25(OH)D levels < 20 ng/ml. Out of the 56 patients (43.75 %) in whom serum 25(OH)D levels ≥20 ng/ml, therapy was unsuccessful in only 5 (8.93 %). Cox regression analysis suggested that serum 25(OH)D levels <20 ng/ml might be an independent risk factor for predicting failure of RIT in GD patients (relative risk = 8.83, 95 % confidence interval = 3.34-23.38, P < 0.001).

CONCLUSIONS

Serum 25(OH)D levels were lower in patients who failed than in those who succeeded in RIT of GD. Therefore, serum 25(OH)D < 20 ng/ml might be an independent risk factor for predicting failure of RIT in GD patients.

Modulation of peanut-induced allergic immune responses by oral lactic acid bacteria-based vaccines in mice

Peanut allergy (PNA) has becoming a non-negligible health concern worldwide. Thus far, allergen-specific immunotherapy aimed at inducing mucosal tolerance has widely been regarded as a major management strategy for PNA. The safety profiles and the intrinsic probiotic properties of lactic acid bacteria (LAB) render them attractive delivery vehicles for mucosal vaccines. In the present study, we exploited genetically modified Lactococcus lactis to produce peanut allergen Ara h 2 via different protein-targeting systems and their immunomodulatory potency for allergic immune responses in mice were investigated. By comparison with the strain expressing the cytoplasmic form of Ara h 2 (LL1), the strains expressing the secreted and anchored forms of Ara h 2 (LL2 and LL3) were more potent in redirecting a Th2-polarized to a non-allergic Th1 immune responses. Induction of SIgA and regulatory T cells were also observed at the local levels by orally administration of recombinant L. lactis. Our results indicate that allergen-producing L. lactis strains modulated allergic immune responses and may be developed as promising mucosal vaccines for managing allergic diseases.

The discovery of how gender influences age immunological mechanisms in health and disease, and the identification of ageing gender-specific biomarkers, could lead to specifically tailored treatment and ultimately improve therapeutic success rates

The control of human health and diseases in the elderly population is becoming a challenge, since mean age and life expectation are progressively increasing as well as chronic degenerative diseases. These disorders are of complex diagnosis and they are difficult to be treated, but it is hoped that the predictive medicine will lead to more specific and effective treatment by using specific markers to identify persons with high risk of developing disease, before the clinical manifestation. Peripheral blood targets and biomarkers are currently the most practical, non-invasive means of disease diagnosing, predicting prognosis and therapeutic response. Human longevity is directly correlated with the optimal functioning of the immune system. Recent findings indicate that the sexual dimorphism of T helper (Th) cytokine pathways and the regulation of Th cell network homeostasis are normally present in the immune response and undergoes to adverse changes with ageing. Furthermore, immune senescence affects both men and women, but it does not affect them equally. Therefore, we hypothesize that the comprehension of the interferences between these gender specific pathways, the ageing immunological mechanism in pathological or healthy state and the current therapies, could lead to specifically tailored treatment and eventually improve the therapeutic success rates. Reaching this aim requires the identification of ageing gender-specific biomarkers that could easily reveal the above mentioned correlations.

T lymphocyte immunity in host defence against Chlamydia trachomatis and its implication for vaccine development

Chlamydia trachomatis is an obligate intracellular bacterial pathogen that causes several significant human infectious diseases, including trachoma, urethritis, cervicitis and salpingitis, and is an important cofactor for transmission of human immunodeficiency virus. Until very recently, over three decades of research effort aimed at developing a C trachomatis vaccine had failed, due mainly to the lack of a precise understanding of the mechanisms for protective immunity. Although most studies concerning protective immunity to C trachomatis have focused on humoral immune responses, recent studies have clearly shown that T helper-1 (Th1)-like CD4 T cell-mediated immune responses play the dominant role in protective immunity. These studies suggest a paradigm for chlamydial immunity and pathology based on the concept of heterogeneity (Th1/Th2) in CD4 T cell immune responses. This concept for chlamydial immunity offers a rational template on which to base renewed efforts for development of a chlamydial vaccine that targets the induction of cell-mediated Th1 immune responses.

Relative vitamin D insufficiency in Hashimoto's thyroiditis

BACKGROUND

Vitamin D insufficiency, defined as serum levels of 25-hydroxyvitamin D [25(OH)D3] lower than 30 ng/mL, has been reported to be prevalent in several autoimmune diseases such as multiple sclerosis and type 1 diabetes mellitus. The goal of the present study was to assess whether vitamin D insufficiency is also a feature of Hashimoto's thyroiditis (HT).

METHODS

We performed a prevalence case-control study that included 161 cases with HT and 162 healthy controls. Serum levels of 25(OH)D3, calcium, phosphorus, and parathyroid hormone were measured in all 323 subjects.

RESULTS

The prevalence of vitamin D insufficiency in HT cases (148 of 161, 92%) was significantly higher than that observed in healthy controls (102 of 162, 63%, p < 0.0001). Among HT cases, the prevalence rate of vitamin D insufficiency showed a trend to be higher in patients with overt hypothyroidism (47 of 50, 94%) or subclinical hypothyroidism (44 of 45, 98%) than in those with euthyroidism (57 of 66, 86%), but the differences were not significant (p = 0.083).

CONCLUSION

Vitamin D insufficiency is associated with HT. Further studies are needed to determine whether vitamin D insufficiency is a casual factor in the pathogenesis of HT or rather a consequence of the disease.

Vitamin D and aging: beyond calcium and bone metabolism

BACKGROUND

Low serum 25-hydroxyvitamin D (25[OH]D) levels are common and may be associated with morbidity and mortality (and indeed with frailty more generally). This association is not restricted to the links between vitamin D and calcium and bone metabolism.

OBJECTIVE

To review the influences of vitamin D on the aging process other than those related to bone and calcium. Its effect on mortality is also assessed.

METHODS

The PubMed database was searched for English-language articles relating to vitamin D, using the following MeSH terms: vitamin D, mortality, cardiovascular diseases, and frailty. In addition, searches were carried out with Google.

RESULTS

Although some of the reported results have proved controversial, overall the evidence seems to support an association between low serum 25[OH]D levels and mortality rates (all-cause and cardiovascular). Frailty is a condition frequently associated with low serum 25[OH]D levels.

CONCLUSION

The aging process and mortality are associated with low vitamin D levels. Prospective controlled trials are warranted to determine whether vitamin D supplements can increase longevity and reduce the incidence of certain conditions.

Role of IL-4 and Th2 responses in allograft rejection and tolerance

PURPOSE OF REVIEW

Due to the dominance of Th1 cytokines in rejection and the ability of Th2 cytokines, particularly IL-4, to inhibit Th1 responses, it has long been held that Th2 cytokines can improve transplant outcomes. Although there is some support for this, there is mounting evidence that IL-4 and Th2 cytokines can promote graft dysfunction. These disparate effects are reviewed.

RECENT FINDINGS

The role of Th2 cytokines in graft dysfunction is not necessarily due to promotion of humoral immunity, but is due to their ability to drive T-cell and non-T-cell responses including alternative activation of macrophages. Alternatively, activated macrophages compete with classically activated macrophages for arginine and they are mutually exclusive, analogous to mutual competition between Th1 and Th2 cells. Recent findings also point to two subsets of regulatory T cells (Tregs), each dependent on either Th1 or Th2 cytokines. In addition to its effects on bone marrow-derived cells, IL-4 affects parenchymal cells by signalling through the type II receptor, which consists of the IL-4R alpha chain (IL-4Ralpha) and the IL-13Ralpha1, which also binds IL-13.

SUMMARY

The effects of Th2 cytokines in transplantation depend on their cellular targets, the timing and form of administration and on Th2 cytokine-dependent Tregs.

Low dose oral administration of cytokines for treatment of allergic asthma

Many inflammatory diseases are characterized by an imbalance among lymphocyte populations, in particular Th1, Th2 and the recently described Th17 cells. The Th1/Th2 imbalance is linked to many factors, but certainly the role of cytokines is essential. In Th2 diseases IL-4 expression is predominant, while Th1 pathologies are characterized by high expression of IFN-gamma and IL-12. Though today the therapeutical proposal for many inflammatory diseases aims to re-establish normal levels of Th1/Th2 cytokines, the pharmacological use of cytokines, which are very active molecules, is limited by the possible collateral effects. Therefore, our study aims to determine, in a murine model of allergic asthma, the possible therapeutic activity of low dose cytokines solutions, mechanically activated. We found that oral administration of low doses IL-12 plus IFN-gamma is able to solve the bronchial hyperresponsiveness condition of mice, establishing normal cytokine levels. The anti-asthma activity was confirmed by histological analysis of lungs and broncho-alveolar lavage fluid cell count. Serum ovalbumin-specific IgE was also significantly inhibited by treatment with low dose activated cytokines solution. These findings may suggest a novel approach to diseases which involve a Th1/Th2 imbalance.

CCL5 regulation of mucosal chlamydial immunity and infection

Background

Following genital chlamydial infection, an early T helper type 1 (Th1)-associated immune response precedes the activation and recruitment of specific Th1 cells bearing distinct chemokine receptors, subsequently leading to the clearance of Chlamydia. We have shown that CCR5, a receptor for CCL5, is crucial for protective chlamydial immunity. Our laboratory and others have also demonstrated that CCL5 deficiencies found in man and animals can increase the susceptibility and progression of infectious diseases by modulating mucosal immunity. These findings suggest the CCR5-CCL5 axis is necessary for optimal chlamydial immunity. We hypothesized CCL5 is required for protective humoral and cellular immunity against Chlamydia.

Results

The present study revealed that CCR5 and CCL5 mRNAs are elevated in the spleen, iliac lymph nodes (ILNs), and genital mucosa following Chlamydia muriduram challenge. Antibody (Ab)-mediated inhibition of CCL5 during genital chlamydial infection suppressed humoral and Th1 > Th2 cellular responses by splenic-, ILN-, and genital mucosa-derived lymphocytes. Antigen (Ag)-specific proliferative responses of CD4⁺ T cells from spleen, ILNs, and genital organs also declined after CCL5 inhibition.

Conclusion

The suppression of these responses correlated with delayed clearance of C. muriduram, which indicate chlamydial immunity is mediated by Th1 immune responses driven in part by CCL5. Taken together with other studies, the data show that CCL5 mediates the temporal recruitment and activation of leukocytes to mitigate chlamydial infection through enhancing adaptive mucosal humoral and cellular immunity.

The role of Helicobacter pylori in gastritis and its progression to peptic ulcer disease

Helicobacter pylori infection is now recognized as the major cause of chronic gastritis throughout the world. A fraction of infected persons develop peptic ulcer disease or gastric cancer, accounting for its clinical significance. The pathophysiology of this infection can be better understood by considering five central concepts--heterogeneity of strains, persistence of infection, immunological down-regulation, physiological consequences and variability in outcome. Microbial, host and environmental factors must each contribute to the outcome variation.

Special regulatory T-cell review: T-cell dependent suppression revisited

The concept of T-cell dependent regulation of immune responses has been a central tenet of immunological thinking since the delineation of the two cell system in the 1960s. Indeed T-cell dependent suppression was discovered before MHC restriction. When reviewing the data from the original wave of suppression, it is intriguing to reflect not just on the decline and fall of suppressor T cells in the 1980s, but on their equally dramatic return to respectability over the past decade. Hopefully their resurgence will be supported by solid mechanistic data that will underpin their central place in our current and future understanding of the immune system. Cannon to right of them, Cannon to left of them, Cannon in front of them Volley'd and thunder'd Storm'd at with shot and shell, Boldly they rode and well, Into the jaws of Death, Into the mouth of Hell, Rode the six hundred (suppressionists). (Adapted from The Charge of the Light Brigade, Alfred, Lord Tennyson)

Trans-sialidase recombinant protein mixed with CpG motif-containing oligodeoxynucleotide induces protective mucosal and systemic trypanosoma cruzi immunity involving CD8+ CTL and B cell-mediated cross-priming

The Trypanosoma cruzi trans-sialidase (TS) is a unique enzyme with neuraminidase and sialic acid transfer activities important for parasite infectivity. The T. cruzi genome contains a large family of TS homologous genes, and it has been suggested that TS homologues provide a mechanism of immune escape important for chronic infection. We have investigated whether the consensus TS enzymatic domain could induce immunity protective against acute and chronic, as well as mucosal and systemic, T. cruzi infection. We have shown that: 1) TS-specific immunity can protect against acute T. cruzi infection; 2) effective TS-specific immunity is maintained during chronic T. cruzi infection despite the expression of numerous related TS superfamily genes encoding altered peptide ligands that in theory could promote immune tolerization; and 3) the practical intranasal delivery of recombinant TS protein combined with a ssDNA oligodeoxynucleotide (ODN) adjuvant containing unmethylated CpG motifs can induce both mucosal and systemic protective immunity. We have further demonstrated that the intranasal delivery of soluble TS recombinant Ag combined with CpG ODN induces both TS-specific CD4(+) and CD8(+) T cells associated with vaccine-induced protective immunity. In addition, optimal protection induced by intranasal TS Ag combined with CpG ODN requires B cells, which, after treatment with CpG ODN, have the ability to induce TS-specific CD8(+) T cell cross-priming. Our results support the development of TS vaccines for human use, suggest surrogate markers for use in future human vaccine trials, and mechanistically identify B cells as important APC targets for vaccines designed to induce CD8(+) CTL responses.

Dendritic cells in allergic airway inflammation

Dendritic cells (DCs) are primary antigen-presenting cells involved in interactions with T cells leading to the proliferation of TH1 or TH2 cell types. In asthma, predominance of TH2 cells appears to be responsible for disease pathogenesis. Differentiation of TH2 cells is driven by a variety of factors such as the expression of high levels of costimulatory molecules, the cytokine profile, and the subset of DCs. Many inflammatory cells involved in the pathogenesis of asthma either directly or indirectly modulate DC function. Traditional treatments for asthma decrease the number of airway DCs in animals as well as in patients with asthma. Immunomodulators including interleukin (IL)-10, transforming growth factor (TGF)-beta, cytosine-phosphate-guanosine-containing oligodeoxynucleotides (CpG-ODN), 1alpha,25-dihydroxyvitamin D3, and fetal liver tyrosine kinase 3 ligand (Flt3L) are involved in the modulation of the function of DCs. Based on the critical review of the interaction between DCs and other inflammatory cells, we propose that activation of T cells by DCs and sensitization to inhaled allergen and resulting airway inflammation are dependent on plasmacytoid and myeloid subset of lung DCs to induce an immune response or tolerance and are tightly regulated by T-regulatory cells. Effects of various therapeutic agents to modulate the function of lung myeloid DCs have been discussed.

Lymphotoxin αβ2 (Membrane Lymphotoxin) Is Critically Important for Resistance toLeishmania majorInfection in Mice

Although the essential role of TNF-alpha in the control of intracellular pathogens including Leishmania major is well established, it is uncertain whether the related cytokine lymphotoxin alphabeta2 (LTalpha1beta2, membrane lymphotoxin) plays any role in this process. In this study, we investigated the contribution of membrane lymphotoxin in host response to L. major infection by using LTbeta-deficient (LTbeta(-/-)) mice on the resistant C57BL/6 background. Despite mounting early immune responses comparable to those of wild-type (WT) mice, LTbeta(-/-) mice developed chronic nonhealing cutaneous lesions due to progressive and unresolving inflammation that is accompanied by uncontrolled parasite proliferation. This chronic disease was associated with striking reduction in IL-12 and Ag-specific IFN-gamma production by splenocytes from infected mice. Consistent with defective cellular immune response, infected LTbeta(-/-) mice had significantly low Ag-specific serum IgG1 and IgG2a levels compared with WT mice. Although administration of rIL-12 to L. major-infected LTbeta(-/-) mice caused complete resolution of chronic lesions, it only partially (but significantly) reduced parasite proliferation. In contrast, blockade of LIGHT signaling in infected LTbeta(-/-) mice resulted in acute and progressive lesion development, massive parasite proliferation, and dissemination to the visceral organs. Although infected LTbeta(-/-) WT bone marrow chimeric mice were more resistant than LTbeta(-/-) mice, they still had reduced ability to control parasites and showed defective IL-12 and IFN-gamma production compared with infected WT mice. These results suggest that membrane lymphotoxin plays critical role in resistance to L. major by promoting effective T cell-mediated anti-Leishmania immunity.

Reversal of polarized T helper 1 and T helper 2 cell populations in murine leishmaniasis

T helper 1 (Th1) and Th2 cells are the major subsets of fully differentiated CD4+ T cells in the mouse. The spectrum of cytokines characteristic of each subset determines the distinctive regulatory and effector functions mediated by each subset. We have used the murine model of Leishmania major infection to study the question of whether highly polarized populations of normal T cells are as stable in their cytokine phenotype as Th clones or whether the phenotype can be altered with regulatory cytokines. Interleukin 4 (IL-4) appears to be a key cytokine for Th2 responses as it is necessary for both the initial differentiation of Th responses to L. major and the stability of ongoing responses. Furthermore, IL-4 is capable of converting highly polarized Th1 responses to Th2 responses either in vitro or when adoptively transferred to severe combined immunodeficiency mice.

Are immunological mechanisms involved in colon cancer and are they possible markers for biotherapy improvement?

This paper focuses on our data on colon cancer patients. Our overall results lead us to believe that the suppressive effect of specific cytokines in colon cancer patients alters the functionality of TH1 and TH2 subsets of CD4+ T-cells, with an expansion of TH2 cells and a malfunctioning of TH1 cells. This immunological disregulation appears to increase with stage progression, suggesting a direct role in the mechanisms that allow the tumour to locate and expand within the host. It is also clear that in order to identify disease markers and generate an in vivo immune response that corrects the imbalance between TH1 and TH2 cells, we need to understand how tumour mechanisms cause this imbalance to begin with.

Colon cancer and gene alterations: their immunological implications and suggestions for prognostic indices and improvements in biotherapy

Studies have shown that changes occur in c-Ki-ras, p53, and Bcl2 gene structure and function during the various stages of human colon carcinogenesis. Alterations of these genes are responsible for the establishment of a state of continuous stimulus for cell division and apoptotic inhibition at physiological and pharmacological levels. This paper focuses on the results of our research aimed at investigating how these gene alterations influence tumoral mechanisms on an immunological level and how immunological parameters can be used as prognostic markers for the passage of normal tissue to adenoma and adenoma to carcinoma. Overall, our data suggest that an alteration in the c-Ki-ras gene results in a switch to a suppressive type of immune response, determining an impairment of immune cell activation at both antigen- presenting-cell and T-cell levels. c-Ki-ras gene mutations, p53 deletions, and Bc12 expression, on the other hand, can be used as prognostic markers for the passage of normal tissue to adenoma and adenoma to carcinoma. The p53 oncogene does not appear to impair patients' immunological response further. In conclusion, an evaluation of c-Ki-ras, rather than p53 gene alterations, would seem to be more relevant in colon cancer prevention programs and biotherapy improvement.

Cytokine secretion profile associated with periportal fibrosis in S. mansoni-infected Egyptian patients

Periportal fibrosis (PPF) is a major pathological consequence of S. mansoni infection. Ultrasonography is a well-established tool for diagnosis and grading of schistosomiasis-related pathology. This work is performed to study the effect of schistosomiasis mansoni infection on the cytokine secretion profile in S. mansoni-infected patients at various grades of fibrosis, as determined by ultrasonography using Cairo Working Group classification. The levels of IL-2, IL-4, IL5, IL-10, IFN-gamma, and TNF-alpha were measured in the absence of in vitro antigen stimulation and after stimulation with worm and egg antigens. Simple intestinal (INT) patients are characterized by strong proliferation to worm antigen and high levels of IL-10 and TNF-alpha compared to patients at various grades of infection. GradeII (GdII)-infected patients are characterized by higher IL-5 production than are patients with other clinical forms of the disease. Sharp reduction of almost all cytokines in response to both worm and egg antigens was detected in GdIII-infected patients. These results stressed the role of both IL-10 and TNF-alpha in the early stages of hepatic fibrosis, while IL-5 could be employed as a potential predictive marker for advanced stages. In conclusion, PPF is associated with cytokine production profiles that vary with the magnitude of the fibrosis.

Differential regulation of IL-2 and IL-4 in patients with tobacco-related oral squamous cell carcinoma

AIM

The aim of the study was to investigate the systemic immunity in terms of major lymphocyte subsets and the expression of IL-2 and IL-4 in T-cell subsets from peripheral blood of patients with tobacco-related intraoral squamous cell carcinoma.

METHODS

CD3+, CD4+ and CD8+ T-cell subsets and CD16+ CD56+ natural killer cells, and intracellular cytokines in T-cell subsets were determined by two-colour flow cytometry and confocal microscopy.

RESULTS

Oral cancer patients showed a significantly reduced (P < 0.001) CD3+ and CD4+ T-cell subsets with a lower CD4/CD8 ratio when compared with the normal controls. The frequency of CD3+ IL-4+ and CD8+ IL-4+ T cells were significantly higher (P < 0.001) while CD4+ IL-2+ were significantly lower (P < 0.02) in patients when compared with the normal controls. Late stage of the tumour was associated with reduced expression of IL-2 in both CD4+ (P < 0.05) and CD8+ (P < 0.03) subsets.

CONCLUSIONS

The tobacco-related intraoral squamous cell carcinoma seems to be associated with multiple systemic immune defects particularly, an impaired CD3+ and CD4+ T cells in the peripheral blood as well as a differential regulation of IL-2 and IL-4 in CD4+ and CD8+ T-cell subsets. The cytokine response in these patients seems to be skewed from protective Th1 to immunosuppressive Th2 type. Thus these patients could be ideal candidate for immunomodulation therapy.

Type 1 and 2 T helper cell-mediated colitis

PURPOSE OF REVIEW

Abrogation of mucosal T cell homeostasis by exaggerated not only T helper 1, but also T helper 2 cells is a major problem that leads to intestinal inflammation. In this regard, it is important to understand these different aspects of mucosal inflammation.

RECENT FINDINGS

Both T helper 1 and 2 cells play central roles in the induction of mucosal immune responses including secretory IgA antibody production, which would be the most beneficial aspect for the host defense mechanism. T helper 1- and 2-type responses, however, exhibit other roles in the abrogation of intestinal homeostasis. Although it has been shown that T helper 1-type immune responses are key players in the induction of intestinal inflammation in mice colitis models and also in inflammatory bowel diseases in humans, studies in murine colitis models clearly show that T helper 2-type responses are also involved in the pathophysiology of the intestinal inflammation. Both regulatory type T cells and T helper 17 cells are involved to down- or upregulate aberrant T helper 1 and 2 cell responses.

SUMMARY

Understanding the cellular and molecular mechanisms of crosstalk among T helper 1, 2, 17 and T regulatory 1 cells is central for the prevention or treatment of inflammatory bowel diseases.

The Study of a Patient's Immune System May Prove to be a Useful Noninvasive Tool for Stage Classification in Colon Cancer

Therapy, and, therefore, prognosis, is strictly related to cancer stage, and hence, screening tests that can contribute to the early classification of disease stage represent a step forward in treatment. Unfortunately, few prognostic indices are available, especially noninvasive ones. Our study of the physiological network of the immune response, however, leads us to believe that it may well be possible to define immunological indices for the classification of cancer stage using blood parameters. In this paper, we show how the study of a patient's immune system can be used as a noninvasive tool for early-stage classification.

Host defence against disseminated Candida albicans infection and implications for antifungal immunotherapy

The different manifestations of Candida albicans infection are dictated by an underlying defect in the immune response of the host. Protective immunity to disseminated candidiasis, the manifestation of C. albicans infection discussed in this review, has traditionally been ascribed to innate immunity with emphasis on the role of granulocytes. Lately, however, immunological studies have learned that host defence against disseminated candidiasis is based on a complex interplay between innate and cell-mediated immunity. Despite the availability of new antifungal agents, mortality associated with disseminated C. albicans infection remains high. Immunotherapy that augments host defence is an important strategic option in the battle against disseminated candidiasis. Here, the authors review the chronological events in the pathogenesis of disseminated candidiasis that aid in predicting the impact of existing immunotherapy and the development of future immunomodulating strategies.

The adjuvant potential of synthetic alkylglycerols

Alkylglycerols (AGs) have shown immune stimulant and adjuvant activity in many studies, but natural sources are not so accessible and their extraction from them is very complicated. Therefore, a group of chemists at IFAL have synthesized AG analogs. The aim of this work was to evaluate the adjuvant potential of different synthetic AGs. A mix of ovoalbumin (Ova) and AGs increase anti-Ova IgG antibodies production in sera of immunized mice. The predominant subclass was IgG1 although higher levels of IgG2a were observed as the carbon chain length of AGs increased. AGs also induced the production of IL-12 and nitric oxide (NO) in the U937 human histiocyte and J774 mouse macrophage cell lines, respectively. These results indicate that synthetic AGs are effective adjuvants for the standardized antigen, Ova.

Oral administration of bovine colostrum stimulates intestinal intraepithelial lymphocytes to polarize Th1-type in mice

Th1 stimulus for Th2-skewed immune response during infancy is important for reduction of incidence of allergic diseases. We examined effects of oral administration of bovine colostrum on local immunity in intestine in adult mice. C57BL/6 mice were orally given bovine colostrum or control milk for 1, 3 or 6 months and intestinal microflora, fecal IgA, and lymphocyte population of gut-associated lymphoid tissues and their abilities of cytokine production were examined. Although the cell populations of intestinal intraepithelial lymphocytes (i-IEL) were not remarkably changed, the T cells in i-IEL were polarized to Th1 type after oral administration of bovine colostrum. Intestinal microflora and IgA levels in feces were not changed by oral administration of bovine colostrum. These results suggest that colostrum stimulates directly to i-IEL to polarize Th1 type, which may protect from infectious diseases and allergic diseases mediated by Th2 type responses.

Type 1 immunity provides both optimal mucosal and systemic protection against a mucosally invasive, intracellular pathogen

It has been hypothesized that optimal vaccine immunity against mucosally invasive, intracellular pathogens may require the induction of different types of immune responses in mucosal and systemic lymphoid tissues. Mucosal type 2/3 responses (producing interleukin-4 [IL-4], IL-6 and/or transforming growth factor beta) could be necessary for optimal induction of protective secretory immunoglobulin A responses. On the other hand, systemic type 1 responses (including gamma interferon [IFN-gamma], tumor necrosis factor alpha, and optimal cytotoxic T-cell responses) are likely to be critical for protection against the disseminated intracellular replication that occurs after mucosal invasion. Despite these predictions, we recently found that vaccines inducing highly polarized type 1 immunity in both mucosal and systemic tissues provided optimal mucosal and systemic protection against the protozoan pathogen Trypanosoma cruzi. To further address this important question in a second model system, we now have studied the capacity of knockout mice to develop protective immune memory. T. cruzi infection followed by nifurtimox treatment rescue was used to immunize CD4, CD8, beta2-microglobulin, inducible nitric oxide synthase (iNOS), IL-12, IFN-gamma, and IL-4 knockout mice. Despite the previously demonstrated importance of CD4(+) T cells, CD8(+) T cells, and nitric oxide for T. cruzi immunity, CD4, CD8, and iNOS knockout mice developed mucosal and systemic protective immunity. However, IL-12, IFN-gamma, and beta2-microglobulin-deficient mice failed to develop mucosal or systemic protection. In contrast, IL-4 knockout mice developed maximal levels of both mucosal and systemic immune protection. These results strongly confirm our earlier conclusion from studies with polarizing vaccination protocols that type 1 immunity provides optimal mucosal and systemic protection against a mucosally invasive, intracellular pathogen.

IFNbeta-1a treatment and reestablishment of Th1 regulation in MS patients: dose effects

The authors evaluated the relationships between clinical and pharmacologic parameters and the Th1/Th2/Th3 cytokine network in patients with relapsing-remitting multiple sclerosis treated with differing doses of interferon-beta1a (IFN-beta1a). Their results show that low doses are ineffective but that high doses restore Th1 regulation of the maturation and activation of monocytes, T cells, immature dendritic cells, dendritic cells, and T regulatory cells for central and peripheral self-tolerance. Interaction between interleukin (IL)-10, IL-12 p70, and IL-6 production appears to play an important role in the control of the maturation and activation states of dendritic cells and T regulatory cells, and is at the basis of the benefit of high doses. The results also indicate that the physiologic mechanisms involved in aging help immunologic reestablishment in IFNbeta-1a-treated patients. Finally, it would appear that the failure of IFNbeta-1a therapy to resolve multiple sclerosis completely is due to the suppression of IL-12 p70 mechanisms (responsible for the physiologic deletion of self-reactive cells) in activation conditions, probably by IFNbeta-1a itself.

Blood monocytes: differing effector role in experimental visceral versus cutaneous leishmaniasis

Irrespective of the tissue infected or the strain involved, all Leishmania species selectively parasitize and replicate within the resident tissue macrophage. Henry Murray here discusses the role of a second mononuclear phagocyte, the blood monocyte, which is also attracted to leishmanial lesions, but which appears to play quite different roles in experimental visceral versus cutaneous infection: in visceral disease, the monocyte is a critical host defense effector cell, in cutaneous disease, it may, paradoxically, serve to perpetuate intracellular infection.

Immunostimulating properties of intragastrically administered Acetobacter-derived soluble branched (1,4)-beta-D-glucans decrease murine susceptibility to Listeria monocytogenes

We previously found that AC-1, an extracellular polysaccharide, produced by Acetobacter xylinum and composed of (1,4)-beta-D-glucan with branches of glucosyl residues, showed a strong activity to induce production of interleukin-12 (IL-12) p40 and tumor necrosis factor alpha by macrophages in vitro via Toll-like receptor 4 (TLR-4) signaling. In the present study, we examined the effect of oral administration of AC-1 on protective immunity against Listeria monocytogenes. Mice were given AC-1 or phosphate-buffered saline (PBS) intragastrically 2 days before, on the day of, and 2 days after an intraperitoneal inoculation of L. monocytogenes. The survival rate of AC-1-treated mice was significantly improved and bacterial growth in AC-1-treated mice was severely retarded compared to those of PBS-treated mice after infection with L. monocytogenes. IL-12 p40 levels in serum and magnitudes of CD4+ Th1 and CD8+ Tc1 responses against Listeria antigen were significantly higher in AC-1-treated mice than in PBS-treated mice. The effect of AC-1 on antilisterial activity was diminished in C3H/HeJ mice carrying mutated TLR-4. Thus, AC-1, a potent IL-12 inducer through TLR-4, enhanced protective immunity against L. monocytogenes via augmentation of Th1 responses. These results suggest that infectious processes driven by intracellular microorganisms could be prevented to develop by the (1,4)-beta-D-glucan.

Homeostatic control of immunity by TCR peptide-specific Tregs

Regulation of the immune response is a multifaceted process involving lymphocytes that function to maintain both self tolerance as well as homeostasis following productive immunity against microbes. There are 2 broad categories of Tregs that function in different immunological settings depending upon the context of antigen exposure and the nature of the inflammatory response. During massive inflammatory conditions such as microbial exposure in the gut or tissue transplantation, regulatory CD4+CD25+ Tregs broadly suppress priming and/or expansion of polyclonal autoreactive responses nonspecifically. In other immune settings where initially a limited repertoire of antigen-reactive T cells is activated and expanded, TCR-specific negative feedback mechanisms are able to achieve a fine homeostatic balance. Here I will describe experimental evidence for the existence of a Treg population specific for determinants that are derived from the TCR and are expressed by expanding myelin basic protein-reactive T cells mediating experimental autoimmune encephalomyelitis, an animal prototype for multiple sclerosis. These mechanisms ensure induction of effective but appropriately limited responses against foreign antigens while preventing autoreactivity from inflicting escalating damage. In contrast to CD25+ Tregs, which are most efficient at suppressing priming or activation, these specific Tregs are most efficient in controlling T cells following their activation.

Vitamin D status, 1,25-dihydroxyvitamin D3, and the immune system

Vitamin D is an important immune system regulator. The active form of vitamin D, 1,25-dihydroxyvitamin D3 [1,25(OH)2D3], has been shown to inhibit the development of autoimmune diseases, including inflammatory bowel disease (IBD). Paradoxically, other immune system-mediated diseases (experimental asthma) and immunity to infectious organisms were unaffected by 1,25(OH)2D3 treatment. There are similar paradoxical effects of vitamin D deficiency on various immune system functions. Vitamin D and vitamin D receptor (VDR) deficiency resulted in accelerated IBD. Experimental asthma was unaffected by 1,25(OH)2D3 treatment and was less severe among VDR-deficient mice. Vitamin D is a selective regulator of the immune system, and the outcome of 1,25(OH)2D3 treatment, vitamin D deficiency, or VDR deficiency depends on the nature of the immune response (eg, infectious disease, asthma, or autoimmune disease). An additional factor that determines the effect of vitamin D status on immune function is dietary calcium. Dietary calcium has independent effects on IBD severity. Vitamin D-deficient mice on low-calcium diets developed the most severe IBD, and 1,25(OH)2D3 treatment of mice on low-calcium diets improved IBD symptoms. However, the best results for IBD were observed when the calcium concentration was high and 1,25(OH)2D3 was administered. Both the type of immune response and the calcium status of the host determine the effects of vitamin D status and 1,25(OH)2D3 on immunity.

Ginseng modulates the immune response by induction of interleukin-12 production

In infections with intracellular microorganisms such as mycobacteria and Leishmania parasites as well as certain extracellular chronic infections such as Pseudomonas aeruginosa a Th1 response with activation of macrophages is desirable. Several studies indicate that such a response is associated with better recovery from infection, improved course of the chronic infection, and higher survival rate. In Th1 responses there is increased interferon-gamma (IFN-gamma) and interleukin-12 (IL-12) production, whereas that of interleukin-10 (IL-10) is decreased. The present study indicated that Ginseng modulation of stimulated peripheral blood mononuclear cells (PBMC) results in a higher IL-12 production. The enhanced IL-12 production could induce a stronger Th1 response, resulting in better protection against infection with a variety of pathogens.

Granulocyte chemotactic protein-2 mediates adaptive immunity in part through IL-8Rbeta interactions

Chemokines constitute a large family of structurally related proteins that play a role in leukocyte migration and differentiation. Indeed, the early expression of human CXC chemokine receptor 1 (hCXCR1) and hCXCR2 [homologous to mouse interleukin (IL)-8Rbeta] ligands by the epithelium is a hallmark of the mucosal host defense. Mice lack IL-8; however, granulocyte chemotactic protein-2 (GCP-2)/lipopolysaccharide-induced CXC chemokine, a murine homologue of human GCP-2, has 32% and 61% sequence identity to human IL-8 and GCP-2, respectively, and binds hCXCR1, hCXCR2, and mouse IL-8Rbeta. To better understand the role of GCP-2 in adaptive immunity and as a nasal adjuvant, we characterized the exogenous effects of this CXC chemokine on cellular and humoral mucosal immune responses. GCP-2 significantly enhanced serum immunoglobulin G (IgG) and mucosal IgA antibodies through increased cytokine secretion by CD4+ T cells. These alterations in humoral and cellular responses were preceded by an increase in the number of B cells in the nasal tract, a decrease in the number of CD4+ T cells in the nasal tract as well as cervical lymph nodes, and an increase in the number of neutrophils in the nasal tract 12 h after GCP-2 immunization. This chemokine also modulated CD28 expression by CD4+ T cells during CD3epsilon stimulation of wild-type mice. GCP-2 increased CD80 and CD86 expression on B cells during in vitro stimulation in a dose-dependent manner. In contrast, cytokine and costimulatory molecule enhancement by GCP-2 was not induced by lymphocytes from IL-8Rbeta-/- mice, suggesting that GCP-2 modulates cellular immunity in part through IL-8Rbeta interactions.

IFN-gamma-inducible chemokines enhance adaptive immunity and colitis

T helper type 1 (Th1) cells secreting interferon-gamma (IFN-gamma) have been closely associated with Crohn's disease (CD). Monokine-induced by IFN-gamma (MIG), IFN-gamma-inducible T cell alpha chemoattractant (I-TAC), and IFN-gamma-inducible protein-10 (IP-10), are chemokines that bind CXCR3 and mediate the chemotaxis of leukocytes. IP-10, MIG, and CXCR3 have been shown to be expressed at sites of CD. The current study stems from our recent findings that IP-10, MIG, and I-TAC significantly contribute to the development of Th1-mediated inflammatory responses. To better understand the role of CXCR3 interactions during CD, we characterized the effects of IP-10, MIG, I-TAC, and CXCR3+ T cells on mucosal immune responses. IP-10, MIG, and I-TAC significantly enhanced antigen-specific serum and mucosal antibodies through Th1-mediated events and CD28 modulation. Additionally, the adoptive transfer of naive CXCR3+ T cells and CD4+CD45RB(HI) to T cell receptor beta (TCRbeta) x delta(-/-) mice resulted in the onset of murine colitis. Taken together, these studies suggest that IP-10, MIG, I-TAC, and CXCR3 interactions are involved in mucosal immune responses required for the induction of CD.

Host-dependent type 1 cytokine responses driven by inactivated viruses may fail to default in the absence of IL-12 or IFN-α/β

Replicating viruses generally induce type 1 immune responses, with high interferon (IFN)-γ levels and antibodies of the IgG2a isotype. In the present study we demonstrate the intrinsic ability of non-replicating virions to induce comparable immune responses in the notable absence of any adjuvant. Injection of inactivated pseudorabies virus, an alphaherpesvirus, by various routes into mice resulted in the generation of T helper (Th) 1 type immune response. Co-delivery of inactivated pseudorabies herpesvirus (iPRV) with protein redirected IgG1-dominated tetanus toxoid-specific responses towards an IgG1/IgG2a balanced response. Also inactivated preparations of viruses from the paramyxo- (Newcastle disease virus), rhabdo- (rabies virus), corona- (infectious bronchitis virus) and reovirus (avian reovirus) families led to IgG2a antibody responses; however, the genetic background of the host did result in considerable variation. Because disrupted virions also induced type 1 immune responses, we conclude that structural elements of virions inherently contribute to IFN-γ-dependent isotype switching by inactivated viruses. Strikingly, immunizations in gene-disrupted mice showed that a functional IFN-α/β, IFN-γ or interleukin (IL)-12 pathway was not required for the generation of a polarized Th1 type immune response initiated by inactivated virus particles. These findings have a bearing on the understanding of immune responsiveness to virus structures and the design of vaccines containing virus components.

Role of interleukin-4 in resistance to Cryptococcus neoformans infection

The role of interleukin (IL)-4 in cryptococcal disease was studied in IL-4 knockout (IL-4KO) and wild-type (WT) mice infected with Cryptococcus neoformans isolates that vary widely in their virulence. Delayed-type hypersensitivity responses were reduced in IL-4KO mice following primary infection with either isolate. Splenic T helper 1 (Th1) cytokine responses were increased in the IL-4KO mice infected with the weakly virulent isolate (184A) but did not change during infection with the highly virulent isolate (NU-2). Th2 cytokine responses (IL-5, IL-10) were downregulated in the IL-4KO mice infected with either isolate. Survival after primary infection with either isolate was not influenced by the absence of IL-4. Fewer colony-forming units were found in the lungs of 184A-infected, IL-4KO mice as compared to WT mice, suggesting that some immunity had developed. IL-4KO mice, primed with small doses of cryptococcal antigen (CneF), had significantly enhanced delayed-type hypersensitivity responses after intravenous infection with 184A and were more resistant to infection compared with WT mice. Increased expression of IL-5 with decreased interferon-gamma contributed to the inability of primed WT mice to resist infection with 184A. Enhanced immunity in the primed IL-4KO mice was reflected in a more moderate increase in IL-5 and IL-10 with maintenance of interferon-gamma levels.

Parenchymal organ, and not splenic, immunity correlates with host survival during disseminated candidiasis

We examined the relationship between host survival and renal and splenic immune responses in a murine model of hematogenously disseminated candidiasis. Male BALB/c mice were infected via tail vein injection with wild-type C. albicans or with an isogenic, Deltaefg1/Deltaefg1 hypha-deficient mutant. Host survival, organ fungal burden, intracellular cytokine content of splenic and kidney lymphocytes, and whole-organ cytokine profiles were determined. Wild-type C. albicans induced type 2 splenocyte responses with both nonfatal and fatal inocula. In the kidney, conversely, wild-type inocula causing no or low mortality induced type 1 responses and 100% fatal inocula induced type 2 or interleukin-10 (IL-10)-dominant responses. Hypha-deficient mutant C. albicans caused no or low mortality while inducing type 1 responses in both the spleen and kidney. To our knowledge, this is the first demonstration that host survival during systemic infection correlates with the type of immune response engendered in a nonlymphoid, parenchymal organ and not with the response in the spleen. Furthermore, the results provide in vivo confirmation that hyphal formation by C. albicans induces type 2 or IL-10-dominant host responses in tissues.

New generation of mucosal adjuvants for the induction of protective immunity

Invasion of infectious agents through mucosal surfaces can be prevented by use of the common mucosal immune system (CMIS), which interconnects inductive tissues, including Peyer's patches (PPs) and nasopharyngeal-associated lymphoreticular tissue (NALT), and effector tissues of the intestinal and respiratory tracts. In order for the CMIS to induce maximal protective mucosal immunity, co-administration of mucosal adjuvant has been shown to be essential. When vaccine antigen is administered together with mucosal adjuvant, antigen-specific T-helper (Th) 1 and Th2 cells, cytotoxic T lymphocytes (CTLs) and IgA B cell responses are effectively induced by oral or nasal routes via the CMIS. In the early stages of induction of mucosal immune response, the uptake of orally or nasally administered antigens is achieved through a unique set of antigen-sampling cells, M cells located in follicle-associated epithelium (FAE) of inductive sites. After successful uptake, the antigens are immediately processed and presented by the underlying dendritic cells (DCs). Elucidation of the molecular/cellular characteristics of M cells and mucosal DCs will greatly facilitate the design of a new generation of effective mucosal adjuvants and of a vaccine delivery vehicle that maximises the use of the CMIS. Our recent efforts at mucosal vaccine development have focused on nasal administration of vaccine antigen together with nontoxic mutant-based or cytokine-/chemokine-based adjuvant for the induction of the protective immunity. To this end, a chimeric form of a nontoxic adjuvant combining the merits of mutant cholera toxin A subunit (mCT-A) and heat labile toxin B subunit (LT-B) was created as the second generation of detoxified toxin-based mucosal adjuvant. When a vaccine antigen was coexpressed together with an immune stimulatory/delivery molecule in crop seed, this edible vaccine is not only effective but also extremely practical in that it can be produced in huge quantities and preserved and shipped over long distances at room temperature without altering the quality of the vaccine. Because such qualities would greatly facilitate global vaccination, this new generation edible vaccines with a built-in adjuvant and/or M cell-targeted edible vaccine promises to be a powerful weapon for combating infectious diseases and bioterrorism.

Intrinsic and extrinsic pathways signaling during HIV-1 mediated cell death

Infection with human immunodeficiency virus (HIV) is characterized by the gradual depletion of CD4+ T lymphocytes. The incorporation of the concept of apoptosis as a rationale to explain progressive T cell depletion has led to growing research in this field during the last 10 years. In parallel, the biochemical pathways implicated in programmed cell death have been extensively studied. Thus, the influence of mitochondrial control in the two major apoptotic pathways-the extrinsic and intrinsic pathways-is now well admitted. In this review, we summarized our current knowledge of the different pathways involved in the death of T cells in the course of HIV infection.

Cytomegalovirus M43 gene modulates T helper cell response

Role of viral genes in modulating T helper 1 (Th1) and T helper 2 (Th2) balance is of principal interest in the study of cytomegalovirus (CMV) immunity. Murine CMV (MCMV) mutants were used to explore a possible mechanism for the ability of virus to induce a predominant Th1 response and to suppress Th2 response by examining the production of Th1 (IFN-gamma, IL-2) and Th2 (IL-4, IL-10) cytokines by the splenocytes of mice infected with wild type (WT) and MCMV mutants. Results (n=6) show that as compared with WT, the MCMV mutant with specific disruption of M43 gene upregulates the production of IL-4 (P=0.0002) and to a lesser extent IL-10 (P=0.015) at 14 days post infection. This indicates that M43 gene may play a role in suppressing Th2 (IL-4) production, especially in the later stage of infection. The IL-4 and IL-10 production during infection with M43 mutant occurs in the presence of a strong IFN-gamma (Th1) response, overriding the cross-regulatory effects of these cytokines within the Th1/Th2 paradigm and suggesting that the predominant response during CMV infection is still a Th1 type response.

IL-12 plays a significant role in the apoptosis of human T cells in the absence of antigenic stimulation

Interleukin-12 (IL-12) is an immunoregulatory cytokine that plays an essential role in cell-mediated immunity. It is known to induce T cell apoptosis in in vivo systems such as graft-versus-host disease (GVHD) and experimental autoimmune uveitis (EAU). However, the role of IL-12 in T cell apoptosis in the absence of antigenic stimulation has not been clearly defined. This study was conducted to investigate whether IL-12, in the absence of an antigen, is able to induce T cell apoptosis, and also, which signalling pathways utilized by IL-12 are involved in this process. Our data clearly showed that IL-12 in the absence of an antigen induces apoptosis in T cells. Flow cytometry and ELISA showed FasL up-regulation and increased IFN-gamma synthesis in IL-12 treated T cells, while Fas and TNF-R1 showed little change. Semi-quantitative RT-PCR demonstrated that IL-12 was able to up-regulate TNF-alpha and FasL mRNA expression. Furthermore, IL-12 induced apoptosis was associated with caspase-3, caspase-2, caspase-7, DNA fragmentation factor 45 (DFF45) and Fas associated death domain (FADD) whereas TNF receptor associated death domain (TRADD) and receptor interacting protein (RIP) were not. Inhibition of Janus tyrosine kinase (JAK) was able to suppress IL-12 induced T cell apoptosis. Anti-FasL antibody was able to block IL-12 induced T cell apoptosis. In conclusion, our findings suggest that IL-12 is able to induce T cell apoptosis in the absence of an antigen. In addition, the present data suggest that this process is FasL mediated and caspase-3 dependent. Furthermore, JAK was shown to be involved in this process. These results may have significant implications in the understanding of IL-12 mediated T cell apoptosis.