Cellular environments and apoptosis: tissue microenvironments control activated T-cell death

Mitochondria during T cell aging

Mitochondrial dysfunction is a hallmark of aging that contributes to inflammaging. It is characterized by alterations of the mitochondrial DNA, reduced respiratory capacity, decreased mitochondrial membrane potential and increased reactive oxygen species production. These primary alterations disrupt other interconnected and important mitochondrial-related processes such as metabolism, mitochondrial dynamics and biogenesis, mitophagy, calcium homeostasis or apoptosis. In this review, we gather the current knowledge about the different mitochondrial processes which are altered during aging, with special focus on their contribution to age-associated T cell dysfunction and inflammaging.

Secondary Bile Acids and Short Chain Fatty Acids in the Colon: A Focus on Colonic Microbiome, Cell Proliferation, Inflammation, and Cancer

Secondary bile acids (BAs) and short chain fatty acids (SCFAs), two major types of bacterial metabolites in the colon, cause opposing effects on colonic inflammation at chronically high physiological levels. Primary BAs play critical roles in cholesterol metabolism, lipid digestion, and host–microbe interaction. Although BAs are reabsorbed via enterohepatic circulation, primary BAs serve as substrates for bacterial biotransformation to secondary BAs in the colon. High-fat diets increase secondary BAs, such as deoxycholic acid (DCA) and lithocholic acid (LCA), which are risk factors for colonic inflammation and cancer. In contrast, increased dietary fiber intake is associated with anti-inflammatory and anticancer effects. These effects may be due to the increased production of the SCFAs acetate, propionate, and butyrate during dietary fiber fermentation in the colon. Elucidation of the molecular events by which secondary BAs and SCFAs regulate colonic cell proliferation and inflammation will lead to a better understanding of the anticancer potential of dietary fiber in the context of high-fat diet-related colon cancer. This article reviews the current knowledge concerning the effects of secondary BAs and SCFAs on the proliferation of colon epithelial cells, inflammation, cancer, and the associated microbiome.

The role of the lipidome in obesity-mediated colon cancer risk

Obesity is a state of chronic inflammation influenced by lipids such as fatty acids and their secondary oxygenated metabolites deemed oxylipids. Many such lipid mediators serve as potent signaling molecules of inflammation, which can further alter lipid metabolism and lead to carcinogenesis. For example, sphingosine-1-phosphate activates cyclooxygenase-2 in endothelial cells resulting in the conversion of arachidonic acid (AA) to prostaglandin E₂ (PGE₂). PGE₂ promotes colon cancer cell growth. In contrast, the less studied path of AA oxygenation via cytochrome p450 enzymes produces epoxyeicosatetraenoic acids (EETs), whose anti-inflammatory properties cause shrinking of enlarged adipocytes, a characteristic of obesity, through the liberation of fatty acids. It is now thought that EET depletion occurs in obesity and may contribute to colon cell carcinogenesis. Meanwhile, gangliosides, a type of sphingolipid, are cell surface signaling molecules that contribute to the apoptosis of colon tumor cells. Many of these discoveries have been made recently and the mechanisms are still not fully understood, leading to an exciting new chapter of lipidomic research. In this review, mechanisms behind obesity-associated colon cancer are discussed with a focus on the role of small lipid signaling molecules in the process. Specifically, changes in lipid metabolite levels during obesity and the development of colon cancer, as well as novel biomarkers and targets for therapy, are discussed.

Is There a Potential Therapeutic Role for Caveolin-1 in Fibrosis?

Fibrosis is a process of dysfunctional wound repair, described by a failure of tissue regeneration and excessive deposition of extracellular matrix, resulting in tissue scarring and subsequent organ deterioration. There are a broad range of stimuli that may trigger, and exacerbate the process of fibrosis, which can contribute to the growing rates of morbidity and mortality. Whilst the process of fibrosis is widely described and understood, there are no current standard treatments that can reduce or reverse the process effectively, likely due to the continuing knowledge gaps surrounding the cellular mechanisms involved. Several cellular targets have been implicated in the regulation of the fibrotic process including membrane domains, ion channels and more recently mechanosensors, specifically caveolae, particularly since these latter contain various signaling components, such as members of the TGFβ and MAPK/ERK signaling pathways, all of which are key players in the process of fibrosis. This review explores the anti-fibrotic influences of the caveola, and in particular the key underpinning protein, caveolin-1, and its potential as a novel therapeutic target.

Differential expression of alarmins-S100A9, IL-33, HMGB1 and HIF-1α in supraspinatus tendinopathy before and after treatment

BACKGROUND

Alarmins, endogenous molecules released on tissue damage have been shown to play an important role in inflammatory musculoskeletal conditions including fracture repair andrheumatoid arthritis. However, the contribution of alarmins to the pathogenesis of tendon disease is not fully understood.

METHODS

We investigated expression of alarmin proteins (S100A9, high-mobility group box 1 (HMGB1) and interleukin-33 (IL-33) and hypoxia-inducible factor 1α (HIF-1α), a subunit of an oxygen sensitive transcription factor, in three cohorts of human supraspinatus tissues: healthy (n=6), painful diseased (n=13) and post-treatment pain-free tendon samples (n=5). Tissue samples were collected during shoulder stabilisation surgery (healthy) or by biopsy needle (diseased/treated). Immunohistochemistry was used to investigate the protein expression of these factors in these healthy, diseased and treated tendons. Kruskal-Wallis with pairwise post hoc Mann-Whitney U tests were used to test for differences in immunopositive staining between these tissue cohorts. Additionally, costaining was performed to identify the cell types expressing HIF-1α, S100A9, IL-33 and HMGB1 in diseased tendons.

RESULTS

Immunostaining showed HIF-1α and S100A9 were increased in diseased compared with healthy and post-treatment pain-free tendons (p<0.05). IL-33 was reduced in diseased compared with healthy tendons (p=0.0006). HMGB1 was increased in post-treatment pain-free compared with healthy and diseased tendons (p<0.01). Costaining of diseased tendon samples revealed that HIF-1α, S100A9 and IL-33 were expressed by CD68+ and CD68- cells, whereas HMGB1 was predominantly expressed by CD68- cells.

CONCLUSIONS

This study provides insight into the pathways contributing to the progressionand resolution of tendon disease. We found potential pro-inflammatory and pathogenic roles for HIF-1α and S100A9, a protective role fornuclear IL-33 and a potentially reparative function for HMGB1 in diseased supraspinatus tendons.

Bioactive Nutrients and Nutrigenomics in Age-Related Diseases

The increased life expectancy and the expansion of the elderly population are stimulating research into aging. Aging may be viewed as a multifactorial process that results from the interaction of genetic and environmental factors, which include lifestyle. Human molecular processes are influenced by physiological pathways as well as exogenous factors, which include the diet. Dietary components have substantive effects on metabolic health; for instance, bioactive molecules capable of selectively modulating specific metabolic pathways affect the development/progression of cardiovascular and neoplastic disease. As bioactive nutrients are increasingly identified, their clinical and molecular chemopreventive effects are being characterized and systematic analyses encompassing the "omics" technologies (transcriptomics, proteomics and metabolomics) are being conducted to explore their action. The evolving field of molecular pathological epidemiology has unique strength to investigate the effects of dietary and lifestyle exposure on clinical outcomes. The mounting body of knowledge regarding diet-related health status and disease risk is expected to lead in the near future to the development of improved diagnostic procedures and therapeutic strategies targeting processes relevant to nutrition. The state of the art of aging and nutrigenomics research and the molecular mechanisms underlying the beneficial effects of bioactive nutrients on the main aging-related disorders are reviewed herein.

Apoptotic effects of tamoxifen on leukocytes from horse peripheral blood and bronchoalveolar lavage fluid

A reduction in inflammatory cell apoptosis is an important concept in the maintenance of inflammation and a potential target for the resolution of inflammation in many inflammatory diseases. Dysregulation of apoptosis has been implicated in a range of diseases, including tumors, neurodegenerative disorders and autoimmunity, and may also be implicated in allergic asthma. In horses, recurrent airway obstruction (RAO) is an asthma-like condition that is characterized increased survival neutrophil bronchial. Tamoxifen is a synthetic, non-steroidal, anti-estrogen agent that is widely used for treating all stages of breast cancer and has been approved for the prevention of breast cancer in high-risk women. The observed efficacy of tamoxifen has been attributed to both growth arrest and the induction of apoptosis. Therefore, the aim of our study was to evaluate the ability of tamoxifen to induce apoptosis in vitro in granulocytic cells from peripheral blood and in mononuclear cells from bronchoalveolar lavage fluid (BALF) in horses. Flow cytometry using commercial AnnexinV-FITC and propidium iodide was used to quantify early and late apoptotic leukocytes, respectively. The results showed a significant increase in early apoptosis in peripheral blood and bronchial granulocytic cells treated with tamoxifen. The rate of early apoptosis of mononuclear cells from blood and BALF when incubated with tamoxifen was significantly lower compared with granulocytic cells. We did not observe a direct effect of tamoxifen on late apoptosis in any of the in vitro assays in the cell types used here. These results indicate that the apoptotic mechanisms under these experimental conditions would affect only blood and BALF granulocytic cells, particularly in early apoptosis. Finally, further in vitro and in vivo studies are needed to better understand apoptotic mechanisms because tamoxifen could be used to treat chronic, inflammatory pathologies associated with granulocytes and allergic diseases, such as asthma or equine RAO.

An aqueous birch leaf extract of Betula pendula inhibits the growth and cell division of inflammatory lymphocytes

ETHNOPHARMACOLOGICAL RELEVANCE

Leaf extracts of Betula pendula have been traditionally used for the treatment of patients with rheumatoid arthritis (RA) or osteoarthritis.

AIM OF THE STUDY

We investigated the anti-proliferative capacity of an aqueous leaf extract of Betula pendula (BPE) on human primary lymphocytes in vitro, because activated lymphocytes play a major role in the initiation and maintenance of RA.

MATERIALS AND METHODS

Lymphocyte proliferation and cell division was measured by the activity of mitochondrial dehydrogenases and by using the membrane-permeable dye carboxyfluorescein diacetate succinimidyl ester (CFSE), respectively. Apoptosis was analyzed by surface staining of phosphatidylserine and intracellular activation of effector caspases 3 and 7 in comparison to the drug methotrexate using flow cytometric and photometrical analysis. In addition, the impact of the extract on cell cycle distribution was investigated by propidium iodide staining of DNA. For the bioassays BPE concentrations of 10-160 μg/mL were investigated. A phytochemical analysis, using LC-MS and HPLC, was conducted to identify the polyphenolic constituents of the birch leaf extract.

RESULTS

Leaf extracts of Betula pendula inhibited the growth and cell division (CD8(+): 40 μg/mL: 45%; 80 μg/mL: 60%; 160 μg/mL: 87%) (CD4(+): 40 μg/mL: 33%; 80 μg/mL: 54%; 160 μg/mL: 79%) of activated, but not of resting T lymphocytes in a significant dose-dependent manner. The inhibition of lymphocyte proliferation due to apoptosis induction (compared to untreated control: 40 μg/mL: 163%; 80 μg/mL: 240%; 160 μg/mL: 348%) and cell cycle arrest was comparable to that of methotrexate. LC-MS analyses showed that the extract contains different quercetin-glycosides.

CONCLUSION

Our results give a rational basis for the use of Betula pendula leaf extract for the treatment of immune disorders, like rheumatoid arthritis, by diminishing proliferating inflammatory lymphocytes.

Are senescence and exhaustion intertwined or unrelated processes that compromise immunity?

Can the immune system be reactivated continuously throughout the lifetime of an organism or is there a finite point at which repeated antigenic challenge leads to the loss of lymphocyte function or the cells themselves or both? Replicative senescence and exhaustion are processes that control T cell proliferative activity and function; however, there is considerable confusion over the relationship between these two intrinsic cellular control mechanisms. In this Opinion article, we compare the molecular regulation of senescence and exhaustion in T cells. Available data suggest that both processes are regulated independently of each other and that it may be safer to block exhaustion than senescence to enhance immunity.

Increased apoptosis of CD4 and CD8 T lymphocytes in the airways of horses with recurrent airway obstruction

Recurrent airway obstruction (RAO, also known as equine heaves) is an inflammatory condition similar to human asthma caused by exposure of susceptible horses to poorly ventilated stable environments. The disease is characterized by neutrophilic airway inflammation, mucus hypersecretion and reversible bronchoconstriction. This inflammatory process is mediated by several factors, including antibodies, cytokines, resident cells of the airway and inflammatory cellular components that arrive in the respiratory tract. An increasing body of evidence has lent support to the concept that a dysregulation of T cell apoptosis may play a central role in the development of airway inflammation and the associated asthma. Therefore, the aim of this study was to investigate early and late apoptosis of CD4 and CD8 T cell subpopulations obtained from the airways of acute RAO-positive animals after exposure to hay/straw. The percentages of CD4 and CD8 T cells and their associated frequencies of apoptosis were quantified using flow cytometry. Hay/straw exposure induced clinical airway obstruction, airway neutrophilia and increased airway mucus production in RAO-positive horses. In addition, allergen exposure increased the percentage of CD4 T cells in RAO-positive horses as well as the frequency of early and late apoptosis in both CD4 and CD8 lymphocyte subpopulations. These results suggest that the higher frequency of lymphocyte apoptosis may play a role in disease progression of horses afflicted with RAO and may partially explain the characteristic remission of this pathological condition once the allergen source is removed. However, further studies are needed to clarify the role of T cell apoptosis in RAO-affected horses.

Immunomodulatory effect of water extract of cinnamon on anti-CD3-induced cytokine responses and p38, JNK, ERK1/2, and STAT4 activation

CONTEXT

Cinnamon bark is a very popular herb used in traditional medicine to treat various disorders such as chronic gastric symptoms, arthritis, and the common cold.

OBJECTIVE

The immunomodulatory effect of water extract of cinnamon bark (CWE) on cytokine secretion and involvement of intracellular signaling molecules in activated T cells have been examined.

MATERIALS AND METHODS

Mice were orally administered CWE for 7 days. Serum was obtained 90 min after intravenous injection of anti-CD3 antibody (Ab). Splenocytes were cultured with anti-CD3 Ab and CWE for cytokine expression, cell cycle, apoptotic/necrotic changes, and viability. IκBα, p38, JNK, ERK1/2, STAT4, and STAT6 were analyzed using western blotting.

RESULTS

Administration of CWE decreased systemic levels of IFN-γ, but not the levels of IL-4 or IL-2. In vitro, CWE inhibited anti-CD3 Ab-stimulated IFN-γ and IL-4 at the mRNA and secreted protein levels. Despite its inhibition of IL-2 transcript, CWE enhanced IL-2 secretion. CWE treatment caused a reduction in the sub-G1 phase, accompanied by an increased ratio of apoptotic cells to necrotic cells. The increased IL-2 secretion by CWE was not mediated by its direct effect on CD4 T cells. CWE inhibited the activation of p38, JNK, ERK1/2, and STAT4, but not IκBα degradation or STAT6.

DISCUSSION AND CONCLUSIONS

These observations provided evidence that CWE was able to down-regulate IFN-γ expression in activated T cells without altering IL-2 production, involving inhibition of p38, JNK, ERK1/2, and STAT4. Our results contribute to a better understanding of the immunomodulatory action of cinnamon bark for the application of inflammatory disorders.

Immune responses to recombinant Brugia malayi pepsin inhibitor homolog (Bm-33) in patients with human lymphatic filariaisis

Immune responses to recombinant Brugia malayi pepsin inhibitor homolog (rBm-33) were investigated in patients with human lymphatic filariasis (microfilaremics (MF) and chronic pathology (CP)) along with endemic normals (EN). Flow cytometric analysis (24 h) revealed CD4(+) T cell activation in patients (MF and CP) compared to normals (EN), with increased expression of CD69 and diminished levels of CD62L and CD127. This was associated with an elevated expression of CD154 but not CD28 and CTLA4 in CP patients. However, Bm-33-induced cytokine expression profile (IL-1β, IL-12, IL-8, IFN-γ, IL-10 and TGF-β) did not exhibit any significant difference between normals and patients at the same time point. Although CD4(+) T cell activation was observed initially in filarial patients (24 h), lymphoproliferation studies (96 h) suggested diminished proliferation compared to normals, indicating functional inactivation in the former upon prolonged antigen exposure. This indicates that rBm-33 induces an early T cell activation in MF and CP patients followed by a decreased lymphoproliferation that might contribute to immune suppression in these individuals.

Role of bacterial pathogens in atopic dermatitis

The skin of atopic dermatitis (AD) patients exhibits a striking susceptibility to colonization and infection with Staphylococcus aureus. This review summarizes our understanding about the role of S. aureus in AD. Indeed, S. aureus colonization is both a cause and a consequence of allergic skin inflammation. The mechanisms that allergic skin inflammation of AD promotes the increase of S. aureus colonization include skin barrier dysfunction, increased synthesis of the extracellular matrix adhesins for S. aureus, and defective innate immune responses due to decreased production of endogenous antimicrobial peptides. On the other hand, the exotoxins secreted by S. aureus are superantigens. Staphylococcal superantigens (SsAgs) may penetrate the skin barrier and contribute to the persistence and exacerbation of allergic skin inflammation in AD through the stimulation of massive T cells, the role of allergens, direct stimulation of antigen-presenting cells and keratinocytes, the expansion of skin-homing cutaneous lymphocyte-associated antigen-positive T cells, and the augmentation of allergen-induced skin inflammation. SsAgs also induce corticosteroid resistance. In therapeutic interventions, anti-inflammatory therapy alone is very effective in reducing S. aureus colonization on the skin, but antibiotic treatment alone is unable to improve the allergic skin inflammation of AD. Therefore, we recommend the combination therapy of anti-inflammatory drugs and antibiotics in the AD patients with secondary bacterial infection, exacerbated AD, or poorly controlled AD. However, when AD is well controlled by anti-inflammatory drugs alone, we do not recommend the antibiotic therapy.

Unrestrained glycogen synthase kinase-3 beta activity leads to activated T cell death and can be inhibited by natural adjuvant

Activated T cell death (ATCD) after peak clonal expansion is required for effective homeostasis of the immune system. Using a mouse model of T cell clonal expansion and contraction, we found that regulation of the proapoptotic kinase glycogen synthase kinase (GSK)-3beta plays a decisive role in determining the extent to which T cells are eliminated after activation. Involvement of GSK-3beta in ATCD was tested by measuring T cell survival after GSK-3beta inhibition, either ex vivo with chemical and pharmacological inhibitors or in vivo by retroviral expression of a dominant-negative form of GSK-3. We also measured amounts of inactivating phosphorylation of GSK-3beta (Ser9) in T cells primed in the presence or absence of LPS. Our results show that GSK-3beta activity is required for ATCD and that its inhibition promoted T cell survival. Adjuvant treatment in vivo maintained GSK-3beta (Ser9) phosphorylation in activated T cells, whereas with adjuvant-free stimulation it peaked and then decayed as the cells became susceptible to ATCD. We conclude that the duration of GSK-3beta inactivation determines activated T cell survival and that natural adjuvant stimulation decreases the severity of clonal contraction in part by keeping a critical proapoptotic regulatory factor, GSK-3beta, inactivated.

Elevated expression of prostaglandin receptor and increased release of prostaglandin E2 maintain the survival of CD45RO+ T cells in the inflamed human pleural space

Throughout the body, the distribution and differentiation of T-cell subsets varies in a way that optimizes host responses. The role of activation-induced cell death (AICD) in altering the distribution of T-lymphocyte subsets at an immune or inflammatory sites has been unexplored. The objective of this study was to assess whether pleural macrophages modulate AICD of specific pleural T-lymphocyte subsets. We found that pleural T-lymphocytes spontaneously undergo apoptosis, which is associated to increased expression of both FAS and FAS ligand, to decreased expression of Bcl 2 and to caspase 8 and 3 activation. While pleural T lymphocytes were partly protected from apoptosis, autologous peripheral blood T lymphocytes increased their apoptosis when cultured with exudative pleural fluids. Pleural CD45RO(+) T cells, in comparison to pleural CD45RA(+) T cells, were more susceptible to apoptosis, but were preferentially protected by exudative pleural fluids. Pleural prostaglandin E 2 (PGE(2)) was implicated in protecting T-lymphocytes from apoptosis because exudative pleural T lymphocytes highly express PGE(2) receptors, and because exudative pleural fluid contained high concentrations of PGE(2). Activated pleural macrophages released PGE(2) and reduced the spontaneous apoptosis of pleural T lymphocytes and depletion of PGE(2) from pleural fluids decreased this protective effect. This study demonstrates that PGE(2), released in the pleural fluids following pleural macrophage activation, prolongs the survival of specific T-cell subsets, resulting in differentiation of the T-cell repertoire within the inflamed pleural space.

Human CD4+ CD25hi Foxp3+ regulatory T cells are derived by rapid turnover of memory populations in vivo

While memory T cells are maintained by continuous turnover, it is not clear how human regulatory CD4+ CD45RO+ CD25hi Foxp3+ T lymphocyte populations persist throughout life. We therefore used deuterium labeling of cycling cells in vivo to determine whether these cells could be replenished by proliferation. We found that CD4+ CD45RO+ Foxp3+ CD25hi T lymphocytes were highly proliferative, with a doubling time of 8 days, compared with memory CD4+ CD45RO+ Foxp3- CD25- (24 days) or naive CD4+ CD45RA+ Foxp3- CD25- populations (199 days). However, the regulatory population was susceptible to apoptosis and had critically short telomeres and low telomerase activity. It was therefore unlikely to be self regenerating. These data are consistent with continuous production from another population source. We found extremely close TCR clonal homology between regulatory and memory CD4+ T cells. Furthermore, antigen-related expansions within certain TCR Vbeta families were associated with parallel numerical increases of CD4+ CD45RO+ CD25hi Foxp3+ Tregs with the same Vbeta usage. It is therefore unlikely that all human CD4+ CD25+ Foxp3+ Tregs are generated as a separate functional lineage in the thymus. Instead, our data suggest that a proportion of this regulatory population is generated from rapidly dividing, highly differentiated memory CD4+ T cells; this has considerable implications for the therapeutic manipulation of these cells in vivo.

[Expression of Fas and Fas-L in renal cell carcinoma]

INTRODUCTION

The previous investigations revealed that Fas-L expression on tumor cells can be one of the reasons of tumor growth, or tumor regression, with or without activation of the immune response.

OBJECTIVE

The objective of our study was to investigate the expression of Fas and Fas-L in situ in normal human renal tissue as well as in different types of renal cell carcinoma (RCC) according to tumor grading.

METHOD

Expression of Fas and Fas-L was examined in 25 RCCs classified according to nuclear grades: G1-G3 and to cell type: 17 clear cells, 3 chromophilics (2 eosinophilics, 1 basophilic), 2 chromophobes and 3 spindle cells. Ten normal human kidneys were analyzed, too. Indirect immunoperoxidase technique was applied. Spread and intensity of staining of Fas and Fas-L molecules expression were scored semiquantitatively.

RESULTS

Distribution of Fas expression in these RCC was typically diffuse. However, Fas-L was almost completely absent in clear cell RCC. In 3 clear cell RCC, some tumor stromal cells exhibited strong expression of Fas-L. On the contrary, chromophilic, chromophobe and spindle cell RCCs grading from G2-G3, manifested variable combinations of Fas and Fas-L expression.

CONCLUSION

The most of clear cell type low grade RCCs manifested intensive and extensive expression of Fas and completely absence of Fas-L. However, RCCs of high grade malignancy belonging to the clear cell, eosinophilic, chromophobe or spindle cell types can have various combinations of Fas and Fas-L expression. It may probably lead to development of different mechanisms of avoidance of immune response to RCC.

Chemokines CCL19 and CCL21 promote activation-induced cell death of antigen-responding T cells

Secondary lymphoid organs (SLOs) provide a niche for the initiation and regulation of T-cell responses, but the mechanisms have been poorly understood. We investigated the influence of chemokines CCL19 and CCL21 constitutively expressed in SLOs on activation-induced cell death (AICD) of CD4+ T cells. When paucity of lymph node T cells (plt) mutant mice lacking expression of CCL19/CCL21 were primed with OVA/CFA, both expansion of OVA-responding CD4+ T cells in the draining lymph nodes and an in vitro recall response were prolonged as compared with responses in wild-type (WT) mice. The apoptotic cell frequency among OVA-responding CD4+ T cells was similarly low in plt/plt and WT mice during the clonal expansion phase. However, during the clonal contraction phase, the frequency never increased in plt/plt mice, whereas in WT mice it continuously increased to a peak 18 days after immunization. The presence of CCL19/CCL21 during the in vitro stimulation of CD4+ T cells with anti-CD3 plus anti-CD28 significantly enhanced in vitro AICD induction of the restimulated T cells, partially through enhancing expression of Fas ligand. Our results suggest that CCL19/CCL21 produced by stromal cells and antigen-presenting cells regulate CD4+ T-cell immune responses in SLOs by promoting AICD.

Granzyme B is critical for T cell receptor-induced cell death of type 2 helper T cells

Although CD95L is required for T cell receptor (TCR)-induced cell death (TCR-ICD) in T helper 1 cells, the molecular mechanisms mediating TCR-ICD in Th2 cells are unknown. We found that death receptors were not involved in TCR-ICD of Th2 cells because blocking their cognate ligands had no effect on apoptosis of activated Th2 cells. Furthermore, we showed that caspases were not actively involved in TCR-ICD of Th2 cells. However, inhibition of granzyme B (GrB) activity abolished TCR-ICD in Th2 cells but not Th1 cells. Likewise, Th2 cells derived from GrB-deficient mice were resistant to TCR-ICD, and GrB deficiency or inhibition of GrB activity consequently enhanced the production of Th2 cytokines. GrB-deficient mice exhibited increased susceptibility to allergen-induced asthma. Thus, GrB plays a critical role in the TCR-ICD of Th2 cells.

Alterations of Mesenchymal and Endothelial Cells in Inflammatory Bowel Diseases

The pathogenesis of complex chronic diseases like inflammatory bowel disease (IBD) can no longer be viewed as a one-way street in which classical immune cells have exclusive control over the initiation, duration and outcome of the disease. There is enough experimental evidence to demonstrate that nonimmune cells, among which are mucosal mesenchymal and endothelial cells, also play a decisive role by interacting with immune cells and establishing a two-way reciprocal exchange of signals and responses that dictate the ultimate outcome of inflammation. Smooth muscle cells and fibroblasts/myofibroblasts display a variety of immune functions and modulate the activity and survival of T-cells. Mucosal microvascular cells, through the expression of adhesion molecules and secretion of chemokines, regulate the quantity and quality of leukocytes transmigrating into the interstitial space. A number of receptor-ligand pairs are expressed by immune and nonimmune cells that control their functional interplay, but the CD40/CD40 ligand system may be the most effective because CD40 is expressed by activated muscle and endothelial cells, while the CD40 ligand is expressed by activated T-cells and platelets. The activation of this system in IBD can lead to the establishment of a continuous cycle of nonimmune cell-dependent, antigen-independent interactions that perpetuates gut inflammation.

Protein kinase C-theta is an early survival factor required for differentiation of effector CD8+ T cells

CD8(+) T cells are crucial for host defense against invading pathogens and malignancies. However, relatively little is known about intracellular signaling events that control the genetic program of their activation and differentiation. Using CD8(+) T cells from TCR-transgenic mice crossed to protein kinase C-theta (PKCtheta)-deficient mice, we report that PKCtheta is not required for Ag-induced CD8(+) T cell proliferation, but is important for T cell survival and differentiation into functional, cytokine-producing CTLs. Ag-stimulated PKCtheta(-/-) T cells underwent accelerated apoptosis associated with deregulated expression of Bcl-2 family proteins and displayed reduced activation of ERKs and JNKs. Some defects in the function of PKCtheta(-/-) T cells (poor survival and reduced Bcl-2 and Bcl-x(L) expression, CTL activity, and IFN-gamma expression) were partially or fully restored by coculture with wild-type T cells or by addition of exogenous IL-2, whereas others (increased Bim(EL) expression and TNF-alpha production) were not. These findings indicate that PKCtheta, although not essential for initial Ag-induced proliferation, nevertheless plays an important role in promoting and extending T cell survival, thereby enabling the complete genetic program of effector CD8(+) differentiation. The requirement for PKCtheta in different types of T cell-dependent responses may, therefore, depend on the overall strength of signaling by the TCR and costimulatory receptors and may reflect, in addition to its previously established role in activation, an important, hitherto unappreciated, role in T cell survival.

FADD deficiency sensitises Jurkat T cells to TNF-alpha-dependent necrosis during activation-induced cell death

Activation-induced cell death (AICD) in activated T lymphocytes is largely mediated by Fas/Fas ligand (FasL) interaction. The cytoplasmic adaptor molecule Fas-associated death domain protein (FADD) plays an essential role in the apoptotic signalling of the Fas death pathway. In the present study, we observed that FADD deficient (FADD(-/-)) Jurkat T cells undergo AICD to a similar extent as wild-type cells. AICD in wild-type Jurkat T cells is via apoptosis, whereas it is non-apoptotic in FADD(-/-) cells. The latter took up propidium iodide, exhibit a loss in mitochondrial membrane potential and have no detectable cleavage products of caspase-8 or -3 activation, suggesting that these cells die by necrosis. Wild-type Jurkat T cells undergo apoptosis when incubated with recombinant FasL and Trail but not with TNF-alpha. In contrast, FADD(-/-) Jurkat T cells are resistant to FasL and Trail but die of necrosis when incubated with TNF-alpha. We showed that neutralising anti-TNF-alpha blocked AICD as well as TNF-alpha-induced necrosis in FADD(-/-) Jurkat T cells. Furthermore, down regulating the receptor interacting protein, RIP, with geldanamycin treatment, which is essential for TNF-alpha signalling, markedly inhibited AICD in FADD(-/-) Jurkat T cells. In addition, caspase-8-deficient Jurkat T cells are resistant to Fas- and TNF-alpha-induced cell death. Taken together, our results suggest that a deficiency in FADD and not caspase-8 or the inhibition of the Fas signalling pathway sensitises Jurkat T cells to TNF-alpha-dependent necrosis during AICD.

Inhibition of lymphocyte apoptosis by pancreatic stellate cells: impact of interleukin-15

There is growing evidence that pancreatic stellate cells (PSCs) produce cytokines and take part in the regulation of inflammatory processes in the pancreas. IL-15 inhibits apoptosis of various cell populations. This study was performed to investigate whether PSCs produce IL-15 and thereby can affect lymphocytes. Primary PSCs were isolated from the rat pancreas using density gradient centrifugation. mRNA expression of IL-15 was demonstrated by RT-PCR, and IL-15 protein was analyzed by immunoblotting. Lymphocytes obtained from rat mesenterial lymph nodes were cocultured with in vitro activated PSCs. Apoptosis has been quantified by the binding of annexin V-FITC with a flow cytometer. Proliferation was monitored using [3H]thymidine incorporation. PSCs express two splice variants of IL-15. The protein was detectable only in cell lysates but not in the cell culture supernatant. Cocultivation of lymphocytes with PSCs and IL-15 inhibited spontaneous lymphocyte apoptosis, and this effect was reduced by an anti-IL-15 antibody. Lymphocytes induced vice versa the proliferation and collagen production of PSCs. The inhibition of spontaneous lymphocyte apoptosis in cocultures with PSCs was at least partially mediated by cell-bound IL-15. This effect and the stimulation of PSCs by lymphocytes may lead to a circulus vitiosus, resulting in the persistence of inflammatory processes and the development of fibrosis during chronic pancreatitis.

Intestinal Fibroblast-Derived IL-10 Increases Survival of Mucosal T Cells by Inhibiting Growth Factor Deprivation- and Fas-Mediated Apoptosis

Mucosal T cells are essential to immune tolerance in the intestine, an organ constantly exposed to large amounts of dietary and bacterial Ags. We investigated whether local fibroblasts affect mucosal T cell survival, which is critical for maintenance of immune tolerance. Coculture with autologous fibroblasts significantly increased viability of mucosal T cells by inhibiting IL-2 deprivation- and Fas-mediated apoptosis, an effect that was both contact- and secreted product-dependent. Investigation of anti-apoptotic factors in the fibroblast-conditioned medium (FCM) revealed the presence of IL-10 and PGE2, but not IFN-beta, IL-2, or IL-15. Although recombinant IFN-beta, but not PGE2, effectively prevented T cell apoptosis, neutralizing Ab studies showed that only IL-10 blockade significantly increased T cells apoptosis, whereas neutralizing IFN-beta or IFN-alpha failed to inhibit the anti-apoptotic effect of FCM. To confirm that fibroblast-derived IL-10 was responsible for preserving mucosal T cell viability, IL-10 mRNA was demonstrated in fibroblasts by Southern blotting and RT-PCR. When FCM was submitted to HPLC fractionation, only the peak matching rIL-10 contained the anti-apoptotic activity, and this was eliminated by treatment with an IL-10-neutralizing Ab. Finally, when fibroblasts were transiently transfected with IL-10 antisense oligonucleotides, the conditioned medium lost its T cell anti-apoptotic effect, whereas medium from fibroblasts transfected with IFN-beta antisense oligonucleotides displayed the same anti-apoptotic activity of medium from untransfected fibroblasts. These results indicate that local fibroblast-derived IL-10 is critically involved in the survival of mucosal T cells, underscoring the crucial importance of studying organ-specific cells and products to define the mechanisms of immune homeostasis in specialized tissue microenvironments like the intestinal mucosa.

Inflammatory cell numbers and cytokine expression in atopic dermatitis after topical pimecrolimus treatment

BACKGROUND

In several clinical trials the topical application of pimecrolimus was shown to be effective in the treatment of atopic dermatitis (AD). By targeting calcineurin-dependent signaling pathways, pimecrolimus controls cytokine gene expression. The purpose of this study was to investigate the effect of pimecrolimus on the inflammatory infiltrate and cytokine expression pattern in AD upon topical therapy.

METHODS

From 10 patients with acute AD, skin biopsies as well as immunophenotype and cytokine production of peripheral blood mononuclear cells (PBMC) were examined before and 3 weeks after therapy.

RESULTS

The clinical improvement was associated with a marked regression of histopathological features. In particular, the density of the inflammatory infiltrate mostly containing lymphocytes and eosinophils declined. By double immunofluorescent staining, a reduced expression of the T helper (Th) 2 cytokines interleukin (IL)-5, IL-10, and IL-13 in both CD4+ and CD8+ T cells was demonstrated after therapy. Pimecrolimus therapy was also associated with a reduced expression of the Th1 cytokine interferon (IFN)-gamma. Interestingly, the numbers of epidermal CD1a+ dendritic cells increased following treatment. In the peripheral blood, a decrease of lymphocytes and eosinophils was noticed, but the distribution of lymphocyte subpopulations and their capacity of cytokine production did not change.

CONCLUSIONS

Topical pimecrolimus exhibits anti-inflammatory effects in AD by reducing the inflammatory cell infiltrate and cytokine expression in the dermis.

Early rheumatoid arthritis is characterized by a distinct and transient synovial fluid cytokine profile of T cell and stromal cell origin

Pathological processes involved in the initiation of rheumatoid synovitis remain unclear. We undertook the present study to identify immune and stromal processes that are present soon after the clinical onset of rheumatoid arthritis (RA) by assessing a panel of T cell, macrophage, and stromal cell related cytokines and chemokines in the synovial fluid of patients with early synovitis. Synovial fluid was aspirated from inflamed joints of patients with inflammatory arthritis of duration 3 months or less, whose outcomes were subsequently determined by follow up. For comparison, synovial fluid was aspirated from patients with acute crystal arthritis, established RA and osteoarthritis. Rheumatoid factor activity was blocked in the synovial fluid samples, and a panel of 23 cytokines and chemokines measured using a multiplex based system. Patients with early inflammatory arthritis who subsequently developed RA had a distinct but transient synovial fluid cytokine profile. The levels of a range of T cell, macrophage and stromal cell related cytokines (e.g. IL-2, IL-4, IL-13, IL-17, IL-15, basic fibroblast growth factor and epidermal growth factor) were significantly elevated in these patients within 3 months after symptom onset, as compared with early arthritis patients who did not develop RA. In addition, this profile was no longer present in established RA. In contrast, patients with non-rheumatoid persistent synovitis exhibited elevated levels of interferon-γ at initiation. Early synovitis destined to develop into RA is thus characterized by a distinct and transient synovial fluid cytokine profile. The cytokines present in the early rheumatoid lesion suggest that this response is likely to influence the microenvironment required for persistent RA.

Transition of late-stage effector T cells to CD27+ CD28+ tumor-reactive effector memory T cells in humans after adoptive cell transfer therapy

In humans, the pathways of memory T-cell differentiation remain poorly defined. Recently, adoptive cell transfer (ACT) of tumor-reactive T lymphocytes to metastatic melanoma patients after nonmyeloablative chemotherapy has resulted in persistence of functional, tumor-reactive lymphocytes, regression of disease, and induction of melanocyte-directed autoimmunity in some responding patients. In the current study, longitudinal phenotypic analysis was performed on melanoma antigen-specific CD8+ T cells during their transition from in vitro cultured effector cells to long-term persistent memory cells following ACT to 6 responding patients. Tumor-reactive T cells used for therapy were generally late-stage effector cells with a CD27Lo CD28Lo CD45RA- CD62 ligand- (CD62L-) CC chemokine receptor 7- (CCR7-) interleukin-7 receptor alphaLo (IL-7RalphaLo) phenotype. After transfer, rapid up-regulation and continued expression of IL-7Ralpha in vivo suggested an important role for IL-7R in immediate and long-term T-cell survival. Although the tumor antigen-specific T-cell population contracted between 1 and 4 weeks after transfer, stable numbers of CD27+)CD28+ tumor-reactive T cells were maintained, demonstrating their contribution to the development of long-term, melanoma-reactive memory CD8+ T cells in vivo. At 2 months after transfer, melanoma-reactive T cells persisted at high levels and displayed an effector memory phenotype, including a CD27+ CD28+ CD62L- CCR7- profile, which may explain in part their ability to mediate tumor destruction.

Defining a role for fibroblasts in the persistence of chronic inflammatory joint disease

The most surprising feature of the inflammatory response in rheumatoid arthritis is not that it occurs but that it does not resolve. The persistence of the chronic inflammatory response in conjunction with ongoing joint destruction is an all too familiar finding in many patients with rheumatoid arthritis. Despite the use of effective anti-inflammatory agents and disease modifying drugs, a significant proportion of patients with rheumatoid arthritis continue to have resistant disease. Complete clinical remission is unusual for more than six months and a formal cure of the disease remains elusive. In this report we focus on how attempts to address the question of why rheumatoid arthritis persists have led to a different interpretation of the pathogenesis of rheumatoid disease; one in which alterations in stromal cells such as fibroblasts play an important role in the switch from resolving to persistent disease.

Inhibition of T cell apoptosis in the aqueous humor of patients with uveitis by IL-6/soluble IL-6 receptor trans-signaling

A fundamental mechanism of immune privilege in the eye is the induction of T lymphocyte apoptosis. Intraocular inflammation in uveitis implies compromise of immune privilege. This study sought to determine whether apoptosis of T cells is actively inhibited in patients with uveitis and by what pathways this may occur. Apoptotic lymphocytes were found to be absent from aqueous humor (AqH) of virtually all patients with recent-onset uveitis. However, T cells removed from the eye were highly susceptible to both spontaneous and Fas ligand-induced apoptosis in vitro. AqH from patients with uveitis had no modulatory effect on Fas ligand-induced apoptosis, but strongly suppressed survival factor deprivation-induced apoptosis. In contrast, noninflammatory AqH from patients undergoing cataract surgery had no modulatory effects on apoptosis at all. These data suggest that triggering of the Fas pathway is diminished in uveitis, and also that homeostatic resolution through survival factor deprivation-induced apoptosis is inhibited by factors present in AqH. The most widely recognized pathways, common gamma-chain cytokines and type I IFNs, did not contribute to AqH-mediated T cell survival. High levels of both IL-6 and soluble IL-6R were found in AqH. IL-6 alone did not induce T cell survival, because IL-6R expression on T cells in AqH was too low to facilitate signaling. However, combinations of IL-6 and soluble IL-6R were highly effective inhibitors of T cell apoptosis, suggesting that the trans-signaling pathway is likely to be a key mediator of T cell apoptosis inhibition mediated by uveitis AqH.

Telomere erosion in memory T cells induced by telomerase inhibition at the site of antigenic challenge in vivo

The extent of human memory T cell proliferation, differentiation, and telomere erosion that occurs after a single episode of immune challenge in vivo is unclear. To investigate this, we injected tuberculin purified protein derivative (PPD) into the skin of immune individuals and isolated responsive T cells from the site of antigenic challenge at different times. PPD-specific CD4⁺ T cells proliferated and differentiated extensively in the skin during this secondary response. Furthermore, significant telomere erosion occurred in specific T cells that respond in the skin, but not in those that are found in the blood from the same individuals. Tissue fluid obtained from the site of PPD challenge in the skin inhibited the induction of the enzyme telomerase in T cells in vitro. Antibody inhibition studies indicated that type I interferon (IFN), which was identified at high levels in the tissue fluid and by immunohistology, was responsible in part for the telomerase inhibition. Furthermore, the addition of IFN-α to PPD-stimulated CD4⁺ T cells directly inhibited telomerase activity in vitro. Therefore, these results suggest that the rate of telomere erosion in proliferating, antigen-specific CD4⁺ T cells may be accelerated by type I IFN during a secondary response in vivo.

Fluticasone induces T cell apoptosis in the bronchial wall of mild to moderate asthmatics

BACKGROUND

Cytokines which signal via the gamma chain of the interleukin (IL)-2 receptor and the interferons (IFNs) have been shown to enhance T cell survival in vitro by rescuing cells from apoptosis.

METHODS

A study was undertaken to determine whether treatment with inhaled fluticasone propionate (FP; 250 microg twice daily) for 2 weeks could modulate production of IL-15 or IFN-beta and thereby affect T cell survival in bronchial tissue of 10 patients with mild/moderate asthma. Bronchial biopsy specimens were taken before and on completion of treatment.

RESULTS

The mean (95% CI) number of T cells per unit area decreased in the asthmatic group following 2 weeks of treatment with FP (from 7.0 (5.6 to 8.4) to 4.5 (4.0 to 5.1); p = 0.001). There was an increase in the percentage of T cells undergoing apoptosis following FP treatment as assessed by T cell/TUNEL staining (from 4.5 (2.6 to 6.4) to 8.7 (6.6 to 10.8); p = 0.0001). The percentage of cells staining for IL-15 and IFN-beta in the lamina propria, determined by an alkaline phosphatase biotin streptavidin technique, decreased significantly from baseline values of 31.6 (23.4 to 39.7) to 19.6 (12.5 to 26.7), p = 0.039 for IL-15 and from 18.9 (13.5 to 24.4) to 9.5 (5.9 to 13.1), p = 0.007 for IFN-beta following 2 weeks of treatment with FP. However, only the decrease in the percentage of cells staining for IL-15 was significantly correlated with an increased number of apoptotic T cells following treatment (p = 0.008).

CONCLUSION

These findings support a novel mechanism for the ability of inhaled corticosteroids to decrease T cell numbers, possibly by downregulation of the cytokine IL-15.

Inhibition of bovine T lymphocyte responses by extracts of the stomach worm Ostertagia ostertagi

Lowered immune responses during bovine ostertagiosis have been reported in both in vivo and in vitro assay systems. In the present study we have employed three different life cycle stages of the nematode Ostertagia ostertagi to determine if products of this economically important parasite inhibit in vitro proliferation of Con A-stimulated cells from uninfected animals. We have demonstrated an inhibitory effect upon the growth of Con A-stimulated lymphocytes after addition of fourth stage larval (L4) soluble extract (L4SE) to the cultures. In contrast, extracts from the third stage larvae (L3) had little or no inhibitory activity. The suppressive products were also shown to be secreted by the late L4. The suppressive activity is reversible if the L4 products are removed from culture. There is no immediate effect on proliferating cells and the L4SE must be in culture for 24-48 h before suppression is observable. The L4SE caused slight but not statistically significant decreases in the percentage of T cells and increases in B cell percentages in cultures when compared with cultures stimulated with Con A alone. No changes were seen in percentage of cells positive for markers for CD4, CD8, gammadelta T cells, or monocytes/macrophages as a consequence of the addition of L4SE. In contrast, there was a strong and significant reduction in the expression of the IL-2 receptors in cells cultured in the presence of the worm extract. There was no evidence of either necrosis or apoptosis resulting from the presence of L4 products in culture. The expression of messenger RNA for interleukin-2, -4, -13, tumor necrosis factor-alpha (TNF-alpha), and gamma-interferon (gamma-IFN) was decreased when L4SE was included in cultures of Con A-stimulated cells compared to cultures stimulated with Con A only. In contrast, messenger RNA expression of transforming growth factor-beta (TGF-beta) and interleukin-10 (IL-10) was increased in cells growing in the presence of L4 products. The potential role of these cytokines during ostertagiosis is discussed.

P-glycoprotein decreases with T cell maturation but is not responsible for resistance to CD95-induced apoptosis

P-glycoprotein (Pgp) is a membrane transporter responsible for resistance to chemotherapy in cancer cells. Its presence in T cells is very well documented, but its function in the immune system is still poorly understood. Recent findings suggest that Pgp may be involved in regulating programmed cell death by inhibiting caspase 8 and caspase 3. Utilising antigenically-activated T cells and the physiologically relevant apoptotic ligand, membrane CD95-L, we have previously reported that while T cells are generally resistant to CD95-induced death at early stages of activation, their susceptibility to apoptosis increases with successive activation and clonal expansion. In this study we investigated whether changes in apoptotic susceptibility were related to T cell Pgp function. Results showed that Pgp expression and function in T cells decreases with maturation, with CD8 cells having the highest Pgp function. However, although Pgp function inversely correlated with caspase 3 activity, no difference was observed between apoptotic susceptible CD25- cells and resistant CD25+ cells. In addition sorting of cells with high and low Pgp function showed no correlation with apoptotic capability. Therefore, whilst Pgp modulates caspase activity, it is not responsible for resistance to apoptosis of early activated T cells nor the increased susceptibility observed at the later stages of maturation in antigenically activated cells.

Proliferation and apoptosis of human CD8+CD28+ and CD8+CD28− lymphocytes during aging

It is commonly believed that the age-related decrease in the ratio CD28(+)/CD28(-) among CD8(+) T cells reflects replicative senescence of the lymphocytes. To verify this claim we measured the proliferation of CD8(+)CD28(+) and CD8(+)CD28(-) subsets by flow cytometry after PHA treatment of mononuclear lymphocytes from donors of different age, including centenarians. The fraction of CD28(+) cells decreases from ca. 80 to 40% (young to centenarians, respectively) with increasing age of the donors. Stimulation by PHA results in an increase in the ratio of CD28(+) relative to CD28(-) in all age groups. We found that not only CD8(+)CD28(+) but also CD8(+)CD28(-) cells were capable of proliferation. Moreover, the fraction of proliferation-competent CD28(-) cells was higher in the older donors compared with the younger ones. While PHA treatment led to apoptosis (as measured by DNA content and caspase-3 activation) of more than 20% of all lymphocytes, in the CD8(+) subset only ca. 10% died, irrespective of their CD28 status. Altogether, we showed over-representation of proliferating CD8(+)CD28(-) cells in aged people, which might not be particularly prone to undergo apoptosis.

Theiler's virus infection: a model for multiple sclerosis

Both genetic background and environmental factors, very probably viruses, appear to play a role in the etiology of multiple sclerosis (MS). Lessons from viral experimental models suggest that many different viruses may trigger inflammatory demyelinating diseases resembling MS. Theiler's virus, a picornavirus, induces in susceptible strains of mice early acute disease resembling encephalomyelitis followed by late chronic demyelinating disease, which is one of the best, if not the best, animal model for MS. During early acute disease the virus replicates in gray matter of the central nervous system but is eliminated to very low titers 2 weeks postinfection. Late chronic demyelinating disease becomes clinically apparent approximately 2 weeks later and is characterized by extensive demyelinating lesions and mononuclear cell infiltrates, progressive spinal cord atrophy, and axonal loss. Myelin damage is immunologically mediated, but it is not clear whether it is due to molecular mimicry or epitope spreading. Cytokines, nitric oxide/reactive nitrogen species, and costimulatory molecules are involved in the pathogenesis of both diseases. Close similarities between Theiler's virus-induced demyelinating disease in mice and MS in humans, include the following: major histocompatibility complex-dependent susceptibility; substantial similarities in neuropathology, including axonal damage and remyelination; and paucity of T-cell apoptosis in demyelinating disease. Both diseases are immunologically mediated. These common features emphasize the close similarities of Theiler's virus-induced demyelinating disease in mice and MS in humans.

Inhibition of fibrocyte differentiation by serum amyloid P

Wound healing and the dysregulated events leading to fibrosis both involve the proliferation and differentiation of fibroblasts and the deposition of extracellular matrix. Whether these fibroblasts are locally derived or from a circulating precursor population is unclear. Fibrocytes are a distinct population of fibroblast-like cells derived from peripheral blood monocytes that enter sites of tissue injury to promote angiogenesis and wound healing. We have found that CD14(+) peripheral blood monocytes cultured in the absence of serum or plasma differentiate into fibrocytes within 72 h. We purified the factor in serum and plasma that prevents the rapid appearance of fibrocytes, and identified it as serum amyloid P (SAP). Purified SAP inhibits fibrocyte differentiation at levels similar to those found in plasma, while depleting SAP reduces the ability of plasma to inhibit fibrocyte differentiation. Compared with sera from healthy individuals and patients with rheumatoid arthritis, sera from patients with scleroderma and mixed connective tissue disease, two systemic fibrotic diseases, were less able to inhibit fibrocyte differentiation in vitro and had correspondingly lower serum levels of SAP. These results suggest that low levels of SAP may thus augment pathological processes leading to fibrosis. These data also suggest mechanisms to inhibit fibrosis in chronic inflammatory conditions, or conversely to promote wound healing.

Apoptosis in feathers of Smyth line chickens with autoimmune vitiligo

Vitiligo is an acquired dermatological disorder characterized by a loss of epidermal melanocytes resulting in depigmentation of the skin. Mechanisms underlying the destruction of melanocytes in vitiligo remain unclear. An animal model to study spontaneously occurring autoimmune vitiligo is the mutant Smyth line (SL) of chickens. This investigation was designed to determine whether the pathogenesis of depigmentation in Smyth line chicken vitiligo (SLV) involves an apoptotic mechanism. Terminal deoxynucleotide transferase-mediated fluorescein-dUTP nick end labeling (TUNEL) was used to detect in situ cell apoptosis in cryostat sections of 2-week-old regenerating feathers. Two-week-old regenerating feathers were obtained from SL chickens and their normally pigmented controls including the parental Brown line (BL) and Light Brown Leghorn (LBL) chickens at 6, 8, 10 and 12 weeks of age. In feathers from vitiliginous SL chickens, the number of TUNEL+ cells was significantly (P<or=0.05) higher than that in the feathers of non-vitiliginous SL, BL or LBL chickens. These TUNEL+ cells were primarily located in the epithelial barb ridge where melanocyte cell bodies are located. The extent of this apoptosis in the feathers of SLV chickens varied with the severity of depigmentation of the feathers (i.e., highest in active depigmentation), suggesting a close association between apoptosis and the disappearance of melanocytes. In addition to TUNEL staining, most sections were double-stained with monoclonal antibodies specific to either CD8 or MHC class II molecules to further explore the relationship between CD8+ feather-infiltrating lymphocytes and this increase in apoptotic cells. Compared to normally pigmented controls, the number of CD8+ and MHC class II+ cells in the feather pulp and the barb ridge increased 2-4 weeks before the visible onset of SLV, and was directly related to the changes in the number of TUNEL+ cells prior to, at onset and during depigmentation. Moreover, some of these infiltrating CD8+ cells were localized next to or near the TUNEL+ cells. These observations suggest that enhanced apoptosis in the feather of SLV chickens is a pathogenic mechanism involved in the death of melanocytes and appears to be induced by infiltrating cytotoxic T lymphocytes (CD8+).

Apoptosis of infiltrating T cells in the central nervous system of mice infected with Theiler's murine encephalomyelitis virus

Theiler murine encephalomyelitis virus (TMEV), DA strain, induces in susceptible strain of mice a biphasic disease consisting of early acute disease followed by late chronic demyelinating disease. Both phases of the disease are associated with inflammatory infiltrates of the central nervous system (CNS). Late chronic demyelinating disease induced by TMEV serves as an excellent model to study human demyelinating disease, multiple sclerosis. During early acute disease, the virus is partially cleared from the CNS by CD3(+) T cells. These T cells express Fas, FasL, negligible levels of Bcl-2 proteins and undergo activation-induced cell death as determined by TUNEL assay leading to resolution of the inflammatory response. In contrast, during late chronic demyelinating disease, and despite dense perivascular and leptomeningeal infiltrates, only very few cells undergo apoptosis. Mononuclear cells infiltrating the CNS express Bcl-2. It appears that the lack of apoptosis of T cells during late chronic demyelinating disease leads to the accumulation of these cells in the CNS. These cells may play a role in the pathogenesis of the demyelinating disease.

Michael Mason prize essay 2003. Why do leucocytes accumulate within chronically inflamed joints?

Chronic inflammation is characterized by the accumulation of leucocytes within tissues. In rheumatoid arthritis the inflammatory infiltrate shares many architectural features with lymphoid tissue. For example, CD4 T cells and B cells accumulate in perivascular lymphoid structures within synovial tissue. CD8 T cells and neutrophils are found predominantly within synovial fluid. What drives these distinctive lymphoid microstructures and the relative contribution of lymphocytes and stromal cells such as fibroblasts to this process is the subject of this review. Cellular interactions between leucocytes and stromal cells such as macrophages and fibroblasts are important in generating tumour necrosis factor-alpha within the inflamed synovium. Therefore understanding how leucocytes accumulate within the inflamed synovium is likely to provide new therapeutic approaches to modify the inflammatory process. We have found that fibroblasts play a dominant role in defining the disordered synovial microenvironment in rheumatoid arthritis. Through their production of a variety of cytokines (interferon-beta, transforming growth factor-beta) and constitutive chemokines (stromal cell-derived factor-1, CXCL12) they directly alter the behaviour of lymphocytes that accumulate within chronically inflamed joints leading to their inappropriate survival and retention. We have extended these observations to another chronic persistent rheumatic disease, Sjögren's syndrome, and found that ectopic production of the constitutive B cell-attracting chemokine BCA-1 (CXCL13) is associated with lymphocyte accumulation and lymphoid tissue formation. These findings suggest that stromal cells such as fibroblasts play an important role in the switch from acute resolving to chronic persistent arthritis by allowing lymphocytes to accumulate in the wrong place at the wrong time.

Induction of CD4+ T cell apoptosis as a consequence of impaired cytoskeletal rearrangement in UVB-irradiated dendritic cells

Low dose UVB irradiation of dendritic cells (DC) dose-dependently decreases their allostimulatory capacity and inhibits alloreactive T cell proliferation. The reduction of the stimulatory capacity is not associated with a perturbation of CD28 costimulation. To examine the underlying mechanism, cell cycle analysis of T cells from cocultures with UVB-irradiated DC (UVB-DC) was performed, revealing no cell cycle arrest, but an increased number of apoptotic T cells in sub-G(0) phase. We confirmed T cells to undergo apoptosis after coincubation with UVB-DC by TUNEL staining and DNA laddering. To analyze whether T cell apoptosis requires the Fas/Fas ligand (FasL) pathway, MLRs were performed with Fas-, FasL-deficient, and wild-type DC and T cells. No differences were found on comparison of wild-type DC with Fas-/FasL-deficient DC or T cells. Likewise, addition of a neutralizing anti-TNF-alpha mAb to cocultures could not overcome inhibition of T cell proliferation by UVB-DC, excluding involvement of the TNF-alpha/TNF-alphaR pathway. FACS analysis of CD69 and CD25 revealed no up-regulation on T cells cocultured with UVB-DC, suggesting a perturbation of early T cell activation. Analysis of UVB-DC by confocal microscopy demonstrated impaired filamentous actin bundling, a process critical for T cell stimulation. To investigate the functional relevance of these observations, time lapse video microscopy was performed. Indeed, calcium signaling in CD4(+) T cells was significantly diminished after interaction with UVB-DC. In conclusion, UVBR of DC impairs their cytoskeletal rearrangement and induces apoptosis in CD4(+) T cells by disruption of early DC-T cell interaction, resulting in a reduced Ca(2+) influx in T cells.

Assessment of oral transmission using cell-free human immunodeficiency virus-1 in mice reconstituted with human peripheral blood leucocyte

Oral-genital contact is one of the risk factors for the transmission of human immunodeficiency virus (HIV) in adults. In recent reports, oral exposure to simian immunodeficiency virus (SIV) was found to have important implications for the achievement of mucosal transmission of HIV in a rhesus monkey animal model. In the present study, we aimed first to establish a small animal model which did not develop tonsils suitable for HIV oral mucosa transmission, using non-obese diabetic/severe combined immunodeficiency (NOD/SCID) mice and NOD/SCID B2m(null) mice grafted with human peripheral blood leucocytes (hu-PBL) and stimulated with interleukin (IL)-4, and second to investigate whether oral exposure to cell-free R5 and X4 HIV-1 could lead to oral transmission of HIV through intact or traumatized mucosal tissues in humanized mice. Both low and high concentrations of cell-free R5 and X4 viruses failed to cause oral transmission with or without trauma in hu-PBL-NOD/SCID and NOD/SCID Beta2m(null) mice, which presented a number of CD4+ cells in gingival tissues and oral cavities with or without tissue injury. The present results show that IL-4-administrated NOD/SCID B2m(null) mice are useful as a small-humanized model for the study of HIV oral infection, which may help to define the window of opportunity for oral transmission by the HIV virus in animal model experiments.

Treating Crohn's disease by inducing T lymphocyte apoptosis

Apoptosis is one of the most important regulatory mechanisms in immunological homeostasis. Disturbances in the apoptotic pathways lead to autoimmune disease. Crohn's disease is a chronic inflammatory bowel disease of unknown origin, which seems to be mediated by excessive T cell-mediated immunity. Recently, disturbances in apoptotic pathways of lamina propria T lymphocytes of patients with Crohn's disease have been identified. In the uninflamed, normal intestinal mucosa, lamina propria (LP) T cells are susceptible to activation-induced cell death, but these cells show a resistance to apoptosis based on several disturbances compared to controls. Recently, intriguing data were published using cytokine-targeted therapy (anti-IL12, anti-IL6 receptor, anti-TNF). Actually, these medications restored mucosal immunological imbalance by inducing apoptosis of the LP T cells and seemed to be beneficial in models of Crohn's disease. In this review, mechanisms of immunological homeostasis will be discussed. We will also discuss the fascinating new results of cytokine-targeted therapy in animal models of Crohn's disease and the effects of these drugs in patients with Crohn's disease.

Effects of human interleukin-18 and interleukin-12 treatment on human lymphocyte engraftment in NOD-scid mouse

NOD/LtSz-prkdc(scid)/prkdc(scid) (non-obese diabetic-severe combine immunodeficiency; NOD-scid) mice grafted with human peripheral blood lymphoid cells have been used as an in vivo humanized mouse model in various studies. However, cytotoxic human T cells are induced in this model during immune responses, which gives misleading results. To assist in grafting of human lymphocytes without the induction of cytotoxic human T cells, we investigated the effects of T helper type 1 (Th1) and Th2 cytokines on human lymphocyte grafting and migration, as well as the production of immunoglobulin deposited in glomeruli and human immunodeficiency virus-1 (HIV-1) infection using NOD-scid mice. Administration of interleukin-18 (IL-18) and IL-12 enhanced the grafting of human CD4+ and CD8+ T cells in the mice, whereas co-administration prevented grafting due to interferon-gamma-dependent apoptosis. Immunoglobulin A (IgA) deposits were observed in mice treated with IL-18 alone, but not in those given phosphate-buffered saline, IL-12 alone, or IL-18 + IL-12. A high rate of HIV infection was also observed in the IL-18-treated group. Together, these results indicate that IL-18 may be effective for the grafting and migration of CD4+ and CD8+ T cells, except for the induction of apoptosis and regulation of class-switching IgA. IL-18-administered NOD-scid mice provide a useful small humanized model for the study of HIV infection and IgA nephropathy.

Glutamine protects activated human T cells from apoptosis by up-regulating glutathione and Bcl-2 levels

Glutamine is the most abundant amino acid in the body. A decrease of plasma glutamine concentrations is found in catabolic stress and is related to susceptibility to infections. Glutamine is known to modulate lymphocyte activation; however, little is known about glutamine modulation of cell death of activated human T cells. Using Jurkat T cells, we investigated glutamine modulation of T-cell apoptosis activated by PMA plus ionomycin. We found that glutamine at various concentrations significantly enhanced IL-2 production, cell proliferation, and cell viability of Jurkat T cells. Glutamine also decreased the number of apoptotic cells stimulated with PMA plus ionomycin as demonstrated by flow cytometry. Meanwhile, glutamine down-regulated CD95 and CD95L expression, but up-regulated CD45RO and Bcl-2 expression in activated T cells. Further investigation of CD95-mediated caspase activities revealed that supplementation of glutamine significantly decreased caspase-3 and caspase-8 activities in activated T cells. Since oxidative stress is closely associated with induction of lymphocyte apoptosis, we found that glutamine significantly increased glutathione (GSH), but decreased reactive oxygen species levels in activated T cells. Blockade of intracellular GSH formation enhanced, but exogenous GSH supplementation decreased, activated T-cell apoptosis. Studying normal peripheral lymphoproliferation, we also found that the presence of glutamine increased lymphoproliferation as well as Bcl-2 and CD95 expression; but decreased CD95L and activation-induced T-cell death. Taken together, glutamine appeared to augment lymphoproliferation but suppressed activation-induced T-cell death in both Jurkat T cells and human peripheral T lymphocytes.

In vivo production of interferon beta by human Tenon's fibroblasts; a possible mediator for the development of chronic conjunctival inflammation

BACKGROUND

Chronic inflammation may develop from failure of the immune system to deactivate itself during resolution of the wound healing response, and is recognised as a major risk factor for trabeculectomy failure. Fibroblast/T cell interactions may contribute to aggressive scarring. Our previous research showed that in vitro human Tenon's fibroblast produced interferon beta was responsible for preventing T cell apoptosis, suggesting that this interaction could contribute to the development of chronic inflammation.

METHODS

Immunohistological techniques were used to investigate the in vivo components of this particular fibroblast/T cell interaction in conjunctival biopsies from glaucoma patients undergoing filtration surgery.

RESULTS

Fibroblast produced interferon beta and T lymphocytes were identified in human conjunctiva.

CONCLUSION

The components of fibroblast mediated prevention of T cell apoptosis were identified in vivo, suggesting that the development of this interaction is possible and that it may contribute to the development of chronic inflammation and excessive scarring.

Apoptosis in acute shigellosis is associated with increased production of Fas/Fas ligand, perforin, caspase-1, and caspase-3 but reduced production of Bcl-2 and interleukin-2

Shigella dysenteriae type 1-induced apoptotic cell death in rectal tissues from patients infected with Shigella dysenteriae type 1 was studied by the terminal deoxynucleotidyltransferase-mediated dUTP-biotin nick end labeling (TUNEL) technique and annexin V staining. Expression of proteins and cytokines participating in the apoptotic process (caspase-1, caspase-3, Fas [CD95], Fas ligand [Fas-L], perforin, granzyme A, Bax, WAF-1, Bcl-2, interleukin-2 [IL-2], IL-18, and granulocyte-macrophage colony-stimulating factor) in tissue in the acute and convalescent stages of dysentery was quantified at the single-cell level by in situ immunostaining. Apoptotic cell death in the lamina propria was markedly up-regulated at the acute stage (P < 0.05), where an increased number of necrotic cells were also seen. Phenotypic analysis of apoptotic cells revealed that 43% of T cells (CD3), 10% of granulocytes (CD15), and 5% of macrophages (CD56) underwent apoptosis. Increased activity of caspase-1 persisted in the rectum up to 1 month after onset. More-extensive expression of Fas, Fas-L, perforin, caspase-3, and IL-18, but not IL-2, at the acute stage than at the convalescent stage was observed. Increased expression of caspase-3 and IL-18 in tissues with severe inflammation compared to expression in those with mild inflammation was evident, implying a possible role in the perpetuation of inflammation. Significantly reduced cell death during convalescence was associated with a significant up-regulation of Bcl-2, Bax, and WAF-1 expression in the rectum compared to that in the acute phase of infection. Thus, induction of apoptosis at the local site in the early phase of S. dysenteriae type 1 infection was associated with a significant up-regulation of Fas/Fas-L and perforin and granzyme A expression and a down-regulation of Bcl-2 and IL-2, which promote cell survival.

Essential role for IL-2 in the regulation of antiviral extralymphoid CD8 T cell responses

IL-2 is a cytokine produced primarily by activated T cells and is thought to be the quintessential T cell growth factor. The precise role of IL-2 in the regulation of CD8 T cell responses to foreign Ag in vivo however remains enigmatic. Using an adoptive transfer system with IL-2- or IL-2R-deficient TCR transgenic CD8 T cells and MHC class I tetramers, we demonstrated that the expansion of antiviral CD8 T cells in secondary lymphoid tissues was IL-2 independent, whereas IL-2 played a more significant role in supporting the continued expansion of these cells within nonlymphoid tissues. Paradoxically, autocrine IL-2 negatively regulated the overall magnitude of the CD8 T cell response in nonlymphoid tissues via a Fas-independent mechanism. Furthermore, autocrine IL-2 did not regulate the contraction or memory phase of the response. These experiments identified a novel role for IL-2 in regulation of antiviral CD8 T cell responses and homeostasis in nonlymphoid tissues.