Different interleukin‐17‐secreting Toll‐like receptor+ T‐cell subsets are associated with disease activity in multiple sclerosis

Signalling through Toll‐like receptors (TLRs) may play a role in the pathogenesis of autoimmune diseases, such as multiple sclerosis (MS). In the present study, the expression of TLR‐2, ‐4 and ‐9 was significantly higher on CD4⁺ and CD8⁺ T‐cells from MS patients compared to healthy individuals. Following in‐vitro activation, the proportion of interleukin (IL)‐17⁺ and IL‐6⁺ CD4⁺ and CD8⁺ T‐cells was higher in the patients. In addition, the proportion of IFN‐γ‐secreting TLR⁺ CD8⁺ T‐cells was increased in MS patients. Among different IL‐17⁺ T‐cell phenotypes, the proportion of IL‐17⁺ TLR⁺ CD4⁺ and CD8⁺ T‐cells producing IFN‐γ or IL‐6 were positively associated with the number of active brain lesions and neurological disabilities. Interestingly, activation of purified CD4⁺ and CD8⁺ T‐cells with ligands for TLR‐2 (Pam3Csk4), TLR‐4 [lipopolysaccharide (LPS)] and TLR‐9 [oligodeoxynucleotide (ODN)] directly induced cytokine production in MS patients. Among the pathogen‐associated molecular patterns (PAMPs), Pam3Csk4 was more potent than other TLR ligands in inducing the production of all proinflammatory cytokines. Furthermore, IL‐6, IFN‐γ, IL‐17 and granulocyte–macrophage colony‐stimulating factor (GM‐CSF) levels produced by Pam3Csk4‐activated CD4⁺ cells were directly associated with disease activity. A similar correlation was observed with regard to IL‐17 levels released by Pam3Csk4‐stimulated CD8⁺ T‐cells and clinical parameters. In conclusion, our data suggest that the expansion of different T helper type 17 (Th17) phenotypes expressing TLR‐2, ‐4 and ‐9 is associated with MS disease activity, and reveals a preferential ability of TLR‐2 ligand in directly inducing the production of cytokines related to brains lesions and neurological disabilities.     

Translational Mini‐Review Series on Immunology of Vascular Disease: Accelerated atherosclerosis in vasculitis

The cutaneous leucocyte‐associated antigen receptor (CLA) can direct Leishmania‐specific T lymphocytes towards inflamed skin lesions. Homing receptors [CLA, lymphocyte‐associated antigen 1 (LFA‐1) or CD62L] were analysed in lymphocytes from blood and cutaneous leishmaniasis (CL) lesions. CL patients with active lesions (A‐CL) presented lower levels of T lymphocytes expressing the CLA⁺ phenotype (T CD4⁺ = 10·4% ± 7·5% and T CD8⁺ = 5·8% ± 3·4%) than did healthy subjects (HS) (T CD4⁺ = 19·3% ± 13·1% and T CD8⁺ = 21·6% ± 8·8%), notably in T CD8⁺ (P < 0·001). In clinically cured patients these percentages returned to levels observed in HS. Leishmanial antigens up‐regulated CLA in T cells (CLA⁺ in T CD4⁺ = 33·3% ± 14·1%; CLA⁺ in T CD8⁺ = 22·4% ± 9·4%) from A‐CL but not from HS. An enrichment of CLA⁺ cells was observed in lesions (CLA⁺ in T CD4⁺ = 45·9% ± 22·5%; CLA⁺ in T CD8⁺ = 46·4% ± 16·1%) in comparison with blood (CLA⁺ in T CD4⁺ = 10·4% ± 7·5%; CLA⁺ in T CD8⁺ = 5·8% ± 3·4%). Conversely, LFA‐1 was highly expressed in CD8⁺ T cells and augmented in CD4⁺ T from peripheral blood of A‐CL patients. In contrast, CD62L was not affected. These results suggest that Leishmania antigens can modulate molecules responsible for migration to skin lesions, potentially influencing the cell composition of inflammatory infiltrate of leishmaniasis or even the severity of the disease.     

Changes in the levels of some acute-phase proteins in human immunodeficiency virus-1 infected patients, following interleukin-2 treatment

Intermittent interleukin (IL)‐2 administration to human immunodeficiency virus (HIV)‐1 infected patients is well documented and generally used, but there is limited information about the changes of acute‐phase protein (APP) levels in response to this treatment. Fifteen patients undergoing highly active anti‐retroviral therapy (HAART) treatment, with undetectable viral load, but low CD4⁺ cell count (<300/µl), have been treated with 3·6 M IU Proleukine® administered twice daily by subcutaneous injection over 5 days. C‐reactive protein (CRP), d ‐dimer, C3, C9, C1‐inh and alpha‐2HS glycoprotein levels were measured immediately before IL‐2 administration, as well as on day 5 and 2–3 weeks thereafter. After IL‐2 administration, both mean d ‐dimer and CRP levels increased significantly (P < 0·001), but returned (P < 0·001) to baseline within the subsequent 2–3 weeks. Alpha‐2HS glycoprotein decreased immediately after IL‐2 administration. No significant differences were detected in the levels of C3, C9 and C1‐inh. A significant, positive correlation (r = 0·5178, P = 0·0008) was ascertained between the changes of CRP level, measured immediately before as well as 5 days after IL‐2 administration, and changes in CD4 T cell counts measured 2–3 weeks before and after treatment, respectively. IL‐2 administration induces rapid elevation of two major APPs (CRP, d ‐dimer). The positive correlation observed between the changes of CRP levels and CD4⁺ cell counts after IL‐2 administration may indicate that the abrupt, but transitory overproduction of CRP might contribute to the CD4⁺ cell count‐increasing effect of the drug and/ or may be associated with serious side effects.     

Unicompartmental and bicompartmental knee osteoarthritis show different patterns of mononuclear cell infiltration and cytokine release in the affected joints

It is still controversial which cell types are responsible for synovial inflammation in osteoarthritic (OA) joints. The aim of this study was to quantify the mononuclear cell populations and their cytokines in patients with different knee OA subtypes. Synovial membrane (SM), synovial fluid (SF) and peripheral blood (PB) were harvested from patients with unicompartmental (UC) and bicompartmental (BC) knee OA. Frequencies of mononuclear cells were assessed by flow cytometry in PB and SM. Naive SF samples were analysed for a broad variety of cytokines by multiplex analysis. SM of both groups displayed a distinct mononuclear cell infiltration, with CD14⁺ macrophages being the major cell population, followed by CD4⁺ T cells and only small numbers of CD8⁺ T, CD19⁺ B and CD16⁺CD56⁺ natural killer (NK) cells. Between the two groups, SM of BC OA showed significantly higher amounts of mononuclear cells (135·7 ± 180 versus 805 ± 675 cells/mg, P = 0·0009) and higher CD4⁺ T cell presence (3·4 ± 4·6 versus 9·1 ± 7·5%, P = 0·0267). SF of BC OA displayed significantly higher concentrations for a number of proinflammatory cytokines [CXCL1, eotaxin, interferon (IFN)‐γ, interleukin (IL)‐7, IL‐8, IL‐9, IL‐12]. UC and BC OA show significant differences in their synovial inflammatory pattern. Whereas in UC OA CD14⁺ macrophages are the predominant cell population, BC OA has a higher inflammatory profile and seems to be driven by CD14⁺ macrophages and CD4⁺ T cells. Inclusion of clinical information into the analysis of cellular and molecular results is pivotal in understanding the pathophysiology of OA.     

Effector memory CD4+ T cells differentially express activation associated molecules depending on the duration of American cutaneous leishmaniasis lesions

A high number of Leishmania‐responder T cells is found in cutaneous leishmaniasis lesions, suggesting that important immunological events occur at the site of infection. Although activated, cytotoxic and regulatory T cells infiltrating into lesions may influence disease pathogenesis, the role of the T cell differentiation pattern of lymphocytes in lesions is unknown. Our aim was to investigate whether the phase of lesion development (early or late) is influenced by the functional status of cells present in inflammatory infiltrate. Activation, cytotoxity and T cell differentiation molecules were evaluated in lesion mononuclear cells by flow cytometry. The frequency of T cells was correlated with the lesion area (r = 0·68; P = 0·020). CD4⁺CD25⁺ T cells predominated over CD4⁺CD69⁺ T cells in early lesions (less than 30 days), whereas late lesions (more than 60 days) exhibited more CD4⁺CD69⁺ T cells than CD4⁺CD25⁺ T cells. The duration of illness was correlated positively with CD4⁺CD69⁺ (r = 0·68; P = 0·005) and negatively with CD4⁺CD25⁺ T cells (r = ?0·45; P = 0·046). Most CD8⁺ T cells expressed cytotoxic‐associated molecules (CD244⁺), and the percentages were correlated with the lesion area (r = 0·52; P = 0·04). Both CD4⁺ and CD8⁺ effector memory T cells (T_EM‐CD45RO⁺CCR7^–) predominated in CL lesions and were significantly higher than central memory (T_CM‐CD45RO⁺CCR7⁺) or naive T cells (CD45RO^–CCR7⁺). An enrichment of T_EM cells and contraction of naive T cells were observed in lesions in comparison to blood (P = 0·006) for both CD4⁺ and CD8⁺ T cells. Lesion chronicity is associated with a shift in activation phenotype. The enrichment of T_EM and activated cytotoxic cells can contribute to immune‐mediated tissue damage.     

Direct recognition of LPS by human but not murine CD8+ T cells via TLR4 complex

LPS comprises a major PAMP and is a key target of the immune system during bacterial infection. While LPS can be recognised by innate immune cells via the TLR4 complex, it is unknown whether T lymphocytes, especially CD8⁺ T cells are also capable of doing so. We report here that naïve human CD8⁺ T cells, after activation by TCR stimulation, express surface TLR4 and CD14. These activated CD8⁺ T cells can then secrete high concentrations of IFN‐γ, granzyme and perforin in response to LPS. These effects can be specifically inhibited using siRNA for TLR4. Furthermore, LPS can synergise with IL‐12 to polarise the CD8⁺ T cells into cytotoxic T‐cell 1 (Tc1) that produce IFN‐γ but not IL‐4, with or without TCR activation. Moreover, CD8⁺CD45RO⁺ memory T cells constitutively expressed TLR4 and markedly enhanced IFN‐γ production when stimulated with LPS. In contrast, activated murine CD8⁺ T cells lack TLR4 and CD14 expression and fail to respond to LPS for proliferation and cytokine production. Thus, human but not murine CD8⁺ T cells are able to directly recognise bacterial LPS via LPS receptor complex and TLR4 provides a novel signal for the activation of effector and memory human CD8⁺ T cells.     

Programmed death (PD)‐1 molecule and its ligand PD‐L1 distribution among memory CD4 and CD8 T cell subsets in human immunodeficiency virus‐1‐infected individuals

Human immunodeficiency virus (HIV)‐1 causes T cell anergy and affects T cell maturation. Various mechanisms are responsible for impaired anti‐HIV‐1‐specific responses: programmed death (PD)‐1 molecule and its ligand PD‐L1 are negative regulators of T cell activity and their expression is increased during HIV‐1 infection. This study examines correlations between T cell maturation, expression of PD‐1 and PD‐L1, and the effects of their blockade. Peripheral blood mononuclear cells (PBMC) from 24 HIV‐1⁺ and 17 uninfected individuals were phenotyped for PD‐1 and PD‐L1 expression on CD4⁺ and CD8⁺ T cell subsets. The effect of PD‐1 and PD‐L1 blockade on proliferation and interferon (IFN)‐γ production was tested on eight HIV‐1⁺ patients. Naive (CCR7⁺CD45RA⁺) CD8⁺ T cells were reduced in HIV‐1 aviraemic (P = 0·0065) and viraemic patients (P = 0·0130); CD8 T effector memory subsets [CCR7^‐CD45RA^–(T_EM)] were increased in HIV‐1⁺ aviraemic (P = 0·0122) and viraemic (P = 0·0023) individuals versus controls. PD‐1 expression was increased in CD4 naive (P = 0·0496), central memory [CCR7⁺CD45RA^– (T_CM); P = 0·0116], T_EM (P = 0·0037) and CD8 naive T cells (P = 0·0133) of aviraemic HIV‐1⁺versus controls. PD‐L1 was increased in CD4 T_EMRA (CCR7^‐CD45RA⁺, P = 0·0119), CD8 T_EM (P = 0·0494) and CD8 T_EMRA (P = 0·0282) of aviraemic HIV‐1⁺versus controls. PD‐1 blockade increased HIV‐1‐specific proliferative responses in one of eight patients, whereas PD‐L1 blockade restored responses in four of eight patients, but did not increase IFN‐γ‐production. Alteration of T cell subsets, accompanied by increased PD‐1 and PD‐L1 expression in HIV‐1 infection contributes to anergy and impaired anti‐HIV‐1‐specific responses which are not rescued when PD‐1 is blocked, in contrast to when PD‐L1 is blocked, due possibly to an ability to bind to receptors other than PD‐1.     

Ro52/TRIM21‐deficient expression and function in different subsets of peripheral blood mononuclear cells is associated with a proinflammatory cytokine response in patients with idiopathic inflammatory myopathies

The presence of anti‐Ro52/tripartite motif 21 (Trim21) autoantibodies has been associated with a distinctive clinical profile and has gained value as a prognostic marker in idiopathic inflammatory myopathies (IIM). The aim of the present work was to analyse Ro52/Trim21 expression in different subsets of peripheral blood mononuclear cells (PBMCs) of patients with IIM, as well as the ubiquitination profile and its association with proinflammatory cytokine production. We included 18 patients with recent‐onset IIM and 18 age‐ and gender‐matched healthy donors. PBMCs were isolated and different subsets (CD4⁺, CD8⁺, CD14⁺) were purified by magnetic selection. The expression of Ro52/Trim21 in different PBMC subsets of patients with IIM and healthy donors was analysed by Western blot. We assessed the presence of myositis‐specific and associated autoantibodies by enzyme‐linked immunosorbent assay (ELISA). Cytokine levels were measured by cytometric bead array. Patients with IIM showed decreased protein expression of Ro52/Trim21 in comparison to healthy controls in PBMC (0·97 ± 0·60 versus 1·84 ± 0·92, P = 0·016), CD4⁺ lymphocytes (0·79 ± 0·54 versus 2·41 ± 0·78, P = 0·017), and monocytes (0·87 ± 0·35 versus 1·89 ± 0·20, P < 0·001). There were no significant differences among IIM groups. Also, a lower K48‐mediated ubiquitination profile was found, predominantly in CD4⁺ lymphocytes. Furthermore, after mitogenic stimulation, there was a higher synthesis of proinflammatory cytokines by T cells [interleukin (IL)‐17A and tumour necrosis factor (TNF)‐α] and monocytes [IL‐6 and interferon (IFN)‐α] from IIM patients compared with healthy controls. Our data suggest that patients with IIM, mainly DM, are characterized by a deficient expression of Ro52/TRIM21 in different PBMC subsets (CD4⁺ lymphocytes and monocytes), along with lower K48‐mediated ubiquitination, which is associated with a proinflammatory cytokine response.     

Evidence for autoantibody-induced CD4 depletion mediated by apoptotic and non-apoptotic mechanisms in HIV-positive long-term surviving haemophilia patients

It is believed that autoimmune phenomena and apoptosis contribute to CD4 depletion. We investigated 11 long‐term (>20 years) HIV‐infected haemophilia patients and 10 healthy controls. Using four‐colour‐fluorescence flow cytometry, we studied the proportions of CD3⁺CD4⁺ and CD3⁺CD4^– blood lymphocytes that were CD95⁺, CD95L⁺, immune complex⁺ (IC⁺, consisting of IgM, IgG, C3d and/or gp120), and were viable or non‐viable (propidium iodide⁺ = PI⁺). In addition, we studied viability of CD4⁺IgG⁺ patient lymphocytes using the apoptosis marker annexin and the permeability indicator 7‐amino actinomycin D (7‐AAD). HIV⁺ patients had a higher proportion of CD3⁺CD4⁺IgG⁺PI⁺ lymphocytes than healthy controls (median: 3·7%versus 0·3%; P = 0·00001). These non‐viable IgG‐coated lymphocytes might have been killed in vivo by ADCC or complement lysis; 9·1% of the circulating CD3⁺CD4⁺ blood lymphocytes were IgG⁺PI^– (controls: 2·5%; P = 0·001). These viable IgG‐coated lymphocytes might be targets for phagocytosis or anti‐CD95 autoantibody‐mediated apoptosis. Because HIV⁺ patients and healthy controls had similar proportions of PI⁺ or PI^– CD3⁺CD4⁺ lymphocytes that carried CD95L on the surface, and because CD3⁺CD4⁺CD95L⁺ cells that were IgG⁺, C3d⁺ and/or gp120^– were increased in HIV⁺ patients, the role of CD95L‐induced apoptosis in long‐term HIV‐infected haemophilia patients remains unclear. The findings that HIV⁺ patients had higher proportions of CD3⁺CD4⁺CD95⁺ (PI⁺: 6·5%versus 1·4%; P = 0·00002; PI^–: 55·8%versus 44·4%; P = 0·04) blood lymphocytes and that the proportion of CD4⁺IgG⁺Annexin⁺7‐AAD^– blood lymphocytes was associated inversely with peripheral CD4 counts (r = ?0·636; P < 0·05) suggest that attachment of IgG to CD4⁺ blood lymphocytes (anti‐CD95?) induces in some lymphocytes apoptosis with subsequent depletion of these IgG‐coated apoptotic CD4⁺ lymphocytes from the circulation. We found supporting evidence for the contention that autoantibody‐induced apoptotic and non‐apoptotic mechanisms contribute to CD4 depletion in long‐term HIV‐infected haemophilia patients.     

T cell activation profiles in different granulomatous interstitial lung diseases – a role for CD8+CD28null cells?

Lymphocytes play a crucial role in lung inflammation. Different interstitial lung diseases may show distinct lymphocyte activation profiles. The aim of this study was to examine the expression of a variety of activation markers on T lymphocyte subsets from blood and bronchoalveolar lavage fluid (BALF) of patients with different granulomatous interstitial lung diseases and healthy controls. Bronchoalveolar lavage cells and blood cells from 23 sarcoidosis patients, seven patients with hypersensitivity pneumonitis and 24 healthy controls were analysed. Lymphocyte activation status was determined by flow cytometry. Lymphocytes were stained with antibodies against CD3, CD4, CD8, CD25, CD28, CD69, very late antigen‐1 (VLA)‐1, VLA‐4 and human leucocyte antigen D‐related (HLA‐DR). In general, CD28, CD69 and VLA‐1 expression on BALF CD4⁺ lymphocytes and HLA‐DR expression on BALF CD8⁺ lymphocytes was different in patients with hypersensitivity pneumonitis and sarcoidosis patients with parenchymal involvement. This BALF lymphocyte phenotype correlated with carbon monoxide diffusing lung capacity (Dlco) values across interstitial lung diseases (ILD) (r² = 0·48, P = 0·0002). In sarcoidosis patients, CD8⁺CD28^null blood lymphocytes correlated with lower Dlco values (r = ?0·66, P = 0·004), chronic BALF lymphocyte activation phenotype (r² = 0·65, P < 0·0001), radiographic staging (stage I versus stage II and higher, P = 0·006) and with the need for corticosteroid treatment (P = 0·001). Higher expression of CD69, VLA‐1 and HLA‐DR and lower expression of CD28 on BALF lymphocytes suggests prolonged stimulation and chronic lymphocyte activation in patients with ILD. In sarcoidosis, blood CD8⁺CD28^null cells might be a new biomarker for disease severity but needs further investigation.     

A novel technique to explore the functions of bronchial mucosal T cells in chronic obstructive pulmonary disease: application to cytotoxicity and cytokine immunoreactivity

Bronchial mucosal CD8⁺ cells are implicated in chronic obstructive pulmonary disease (COPD) pathogenesis, but there are few data on their functional properties. We have developed a novel technique to outgrow these cells from COPD patients in sufficient numbers to examine effector functions. Endobronchial biopsies from 15 COPD smokers and 12 ex‐smokers, 11 control smokers and 10 non‐smokers were cultured with anti‐CD3/interleukin (IL)‐2 ± IL‐15. Outgrown CD3⁺ T cells were characterized in terms of phenotype (expression of CD4, 8, 25, 28, 69 and 56), cytotoxicity and expression of COPD‐related cytokines. Compared with IL‐2 alone, additional IL‐15 increased the yield and viability of biopsy‐derived CD3⁺ T cells (12–16‐day culture without restimulation) without alteration of CD4⁺/CD8⁺ ratios or expression of accessory/activation molecules. Biopsy‐derived T cells, principally CD8⁺/CD56⁺ cells, exhibited statistically significantly greater cytotoxic activity in current or ex‐smokers with COPD compared with controls (P < 0·01). Elevated percentages of CD8⁺ T cells expressed interferon (IFN)‐γ, tumour necrosis factor (TNF)‐α and IL‐13 (P < 0·01) in current COPD smokers compared with all comparison groups. It is possible to perform functional studies on bronchial mucosal T cells in COPD. We demonstrate increased CD8⁺CD56⁺ T cell cytotoxic activity and expression of remodelling cytokines in smokers who develop COPD.     

Low numbers of CD8+ T lymphocytes in hereditary haemochromatosis are explained by a decrease of the most mature CD8+ effector memory T cells

Low CD8⁺ T lymphocyte numbers have long been described in hereditary haemochromatosis (HH). Recently, two conserved haplotypes localized near the microsatellite D6S105 at the major histocompatibility complex (MHC) class I region were described predicting the clinical expression of HH and the CD8⁺ T lymphocyte numbers. The A‐A‐T haplotype was associated with a severe clinical expression of HH and low CD8⁺ T lymphocyte numbers, while the G‐G‐G haplotype was associated with a milder clinical expression of HH and high CD8⁺ T lymphocyte numbers. As CD8⁺ T lymphocytes are a very heterogeneous population, in this study we analysed the CD8⁺ subpopulations of naive, central memory (T_CM) and effector memory (T_EM), and further subsets of CD8⁺ T_EM cells in 47 HH patients and 68 controls. In addition, association studies were conducted between the conserved haplotypes and the CD8⁺ T cell subpopulations in HH. Variations of the numbers of naive and central memory cells with age were similar between HH patients and controls. For T_EM cells and the T_EM CD27^‐CD28^‐ subset no effect of age was observed in HH [R² = 0·001, not significant (n.s.) and R² = 0·01, n.s., respectively] contrasting with the increasing of these subpopulations with age in controls (R² = 0·09, P = 0·017 and R² = 0·22, P = 0·0005, respectively). Interestingly, patients homozygous for the A‐A‐T haplotype have lower numbers of CD8⁺ T_EM cells due especially to lower numbers of T_EM CD27^‐CD28^‐ (0·206 ± 0·119 and 0·066 ± 0·067 × 10⁶ cells/ml, respectively) than patients carrying the G‐G‐G haplotype (0·358 ± 0·195 and 0·246 ± 0·202 × 10⁶ cells/ml, respectively). This may suggest an inability of HH patients to differentiate the CD8⁺ T cells into the most mature phenotype.     

Lack of SIGIRR/TIR8 aggravates hydrocarbon oil‐induced lupus nephritis

Multiple genetic factors contribute to the clinical variability of spontaneous systemic lupus erythematosus (SLE) but their role in drug‐induced SLE remain largely unknown. Hydrocarbon oil‐induced SLE depends on mesothelial cell apoptosis and Toll‐like receptor (TLR)‐7‐mediated induction of type I interferons. Hence, we hypothesized that TIR8/SIGIRR, an endogenous TLR inhibitor, prevents oil‐induced SLE. Sigirr‐deficient dendritic cells expressed higher TLR7 mRNA levels and TLR7 activation resulted in increased IL‐12 production in vitro. In vivo, lack of SIGIRR increased surface CD40 expression on spleen CD11c⁺ dendritic cells and MX‐1, TNF, IL‐12, BAFF and BCL‐2 mRNA expression 6 months after pristane injection. Spleen cell counts of CD4^?/CD8^? ‘autoreactive’ T cells and B220⁺ B cells were also increased in Sigirr^?/? mice. Serum autoantibody analysis revealed that Sigirr deficiency specifically enhanced the production of rheumatoid factor (from 4 months of age) and anti‐snRNP IgG (from 5 months of age), while anti‐Smith IgG or anti‐dsDNA IgG were independent of the Sigirr genotype. This effect was sufficient to significantly aggravate lupus nephritis in Sigirr‐deficient mice. Structure model prediction identified the BB loop of SIGIRR's intracellular TIR domain to interact with TLR7 and MyD88. BB loop deletion was sufficient to completely abrogate SIGIRR's inhibitory effect on TLR7 signalling. Thus, TIR8/SIGIRR protects from hydrocarbon oil‐induced lupus by suppressing the TLR7‐mediated activation of dendritic cells, via its intracellular BB loop. Copyright © 2009 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.     

Low thymic output in the 22q11.2 deletion syndrome measured by CCR9+CD45RA+ T cell counts and T cell receptor rearrangement excision circles

Thymic hypoplasia is a frequent feature of the 22q11.2 deletion syndrome, but we know little about patients' age‐related thymic output and long‐term consequences for their immune system. We measured the expression of T cell receptor rearrangement excision circles (TREC) and used flow cytometry for direct subtyping of recent thymic emigrant (RTE)‐related T cells in 43 patients (aged 1–54 years; median 9 years) from all over Norway and in age‐matched healthy controls. Thymic volumes were estimated by ultrasound in patients. TREC levels correlated well with RTE‐related T cells defined by co‐expression of CD3, CD45RA and CCR9 (r = 0·84) as well as with the CD4⁺ and CD8⁺ T cell subtypes. RTE‐related T cell counts also paralleled age‐related TREC reductions. CD45RA⁺ T cells correlated well with absolute counts of CD4⁺ (r = 0·87) and CD8⁺ (r = 0·75) RTE‐related T cells. Apart from CD45RA^‐ T cells, all T cell subsets were lower in patients than in controls. Thymic volumes correlated better with RTE‐related cells (r = 0·46) than with TREC levels (r = 0·38). RTE‐related T cells and TREC levels also correlated well (r = 0·88) in patients without an identifiable thymus. Production of RTEs is impaired in patients with a 22q11.2 deletion, and CCR9 appears to be a good marker for RTE‐related T cells.     

Association between discordant immunological response to highly active anti‐retroviral therapy,regulatory T cell percentage,immune cell activation and very low‐level viraemia in HIV‐infected patients

The mechanisms sustaining the absence of complete immune recovery in HIV‐infected patients upon long‐term effective highly active anti‐retroviral therapy (HAART) remain elusive. Immune activation, regulatory T cells (T_regs) or very low‐level viraemia (VLLV) have been alternatively suspected, but rarely investigated simultaneously. We performed a cross‐sectional study in HIV‐infected aviraemic subjects (mean duration of HAART: 12 years) to concomitantly assess parameters associated independently with inadequate immunological response. Patients were classified as complete immunological responders (cIR, n = 48) and inadequate immunological responders (iIR, n = 39), depending on the CD4⁺ T cell count (> or < 500/mm³). Clinical and virological data (including very low‐level viraemia) were collected. In parallel, immunophenotyping of CD4⁺ lymphocytes, including T_reg subsets, and CD8⁺ T cells was performed. Percentages of activated CD4⁺ T cells, T_regs, effector T_regs and terminal effector T_regs were found to be significantly elevated in iIR. Neither the percentage of activated CD8⁺ T cells nor VLLV were found to be associated with iIR. In the multivariate analysis, nadir of CD4⁺ T cell count and percentage of T_regs were the only two parameters associated independently with iIR [odds ratio (OR) = 2·339, P = 0·001, and OR = 0·803, P = 0·041]. We present here the largest study investigating simultaneously the immune response to long‐term HAART, activation of CD4⁺ and CD8⁺ T cells, T_reg percentages and very low‐level viraemia. Causative interactions between T_regs and CD4⁺ T cells should now be explored prospectively in a large patients cohort.     

Characteristics of Schistosoma japonicum infection induced IFN‐γ and IL‐4 co‐expressing plasticity Th cells

Schistosoma japonicum infection can induce granulomatous inflammation and cause tissue damage in the mouse liver. The cytokine secretion profile of T helper (Th) cells depends on both the nature of the activating stimulus and the local microenvironment (e.g. cytokines and other soluble factors). In the present study, we found an accumulation of large numbers of IFN‐γ⁺ IL‐4⁺ CD4⁺ T cells in mouse livers. This IFN‐γ⁺ IL‐4⁺ cell population increased from 0·68 ± 0·57% in uninfected mice to 7·05 ± 3·0% by week 4 following infection and to 9·6 ± 5·28% by week 6, before decreasing to 6·3 ± 5·9% by week 8 in CD4 T cells. Moreover, IFN‐γ⁺ IL‐4⁺ Th cells were also found in mouse spleen and mesenteric lymph nodes 6 weeks after infection. The majority of the IFN‐γ⁺ IL‐4⁺ Th cells were thought to be related to a state of immune activation, and some were memory T cells. Moreover, we found that these S. japonicum infection‐induced IFN‐γ⁺ IL‐4⁺ cells could express interleukin‐2 (IL‐2), IL‐9, IL‐17 and high IL‐10 levels at 6 weeks after S. japonicum infection. Taken together, our data suggest the existence of a population of IFN‐γ⁺ IL‐4⁺ plasticity effector/memory Th cells following S. japonicum infection in C57BL/6 mice.     

TLR8‐mediated activation of human monocytes inhibits TL1A expression

TLR play important roles in inflammation and innate immune response to pathogens. TLR8 recognizes ssRNA and induces NF‐κB via MyD88 signaling. TL1A is a member of the TNF superfamily that markedly enhances IFN‐γ production by IL‐12/IL‐18‐stimulated peripheral and mucosal CD4⁺ T cells. TL1A expression is increased in the mucosa of patients with inflammatory bowel disease and is considered a key mediator of Crohn's disease (CD). We have previously shown that TL1A is strongly induced by immune complexes (IC) but not TLR ligands in antigen‐presenting cells. However, a potential interaction between these pro‐inflammatory signaling pathways has not been investigated. IC‐induced TL1A expression of monocytes was potently inhibited by a TLR8 or TLR7/8 ligand (R848) in a dose‐dependent manner. Furthermore, when co‐cultured with CD4⁺ T cells, TLR8 ligands inhibited TL1A production, resulting in almost complete inhibition of IFN‐γ production by the CD4⁺ T cells. Furthermore, we demonstrate that IFN‐α is not required for this suppressive effect by TLR8 signaling. Our data demonstrate for the first time a direct interaction between TLR and TL1A signaling pathways. TLR8 activation may be an important, novel pathway for targeted treatment of Th1‐mediated diseases, such as CD.