Cell-to-cell interactions and signals involved in the reconstitution of peripheral CD8 T(CM) and T(EM) cell pools

We here describe novel aspects of CD8⁺ and CD4⁺ T cell subset interactions that may be clinically relevant and provide new tools for regulating the reconstitution of the peripheral CD8⁺ T cell pools in immune-deficient states. We show that the reconstitution capacity of transferred isolated naïve CD8⁺ T cells and their differentiation of effector functions is limited, but both dramatically increase upon the co-transfer of CD4⁺ T cells. This helper effect is complex and determined by multiple factors. It was directly correlated to the number of helper cells, required the continuous presence of the CD4⁺ T cells, dependent on host antigen-presenting cells (APCs) expressing CD40 and on the formation of CD4/CD8/APC cell clusters. By comparing the recovery of (CD44⁺CD62L^high) T_CM and (CD44⁺CD62L^low) T_EM CD8⁺ T cells, we found that the accumulation of T_CM and T_EM subsets is differentially regulated. T_CM-cell accumulation depended mainly on type I interferons, interleukin (IL)-6, and IL-15, but was independent of CD4⁺ T-cell help. In contrast, T_EM-cell expansion was mainly determined by CD4⁺ T-cell help and dependent on the expression of IL-2Rβ by CD8 cells, on IL-2 produced by CD4⁺ T-cells, on IL-15 and to a minor extent on IL-6.     

Impaired thymic export and apoptosis contribute to regulatory T-cell defects in patients with chronic heart failure

Objective

Animal studies suggest that regulatory T (T_reg) cells play a beneficial role in ventricular remodeling and our previous data have demonstrated defects of T_reg cells in patients with chronic heart failure (CHF). However, the mechanisms behind T_reg-cell defects remained unknown. We here sought to elucidate the mechanism of T_reg-cell defects in CHF patients.

Methods and Results

We performed flow cytometry analysis and demonstrated reduced numbers of peripheral blood CD4⁺CD25⁺FOXP3⁺CD45RO⁻CD45RA⁺ naïve T_reg (nT_reg) cells and CD4⁺CD25⁺FOXP3⁺CD45RO⁺CD45RA⁻ memory T_reg (mT_reg) cells in CHF patients as compared with non-CHF controls. Moreover, the nT_reg/mT_reg ratio (p<0.01), CD4⁺CD25⁺FOXP3⁺CD45RO⁻ CD45RA⁺CD31⁺ recent thymic emigrant T_reg cell (RTE-T_reg) frequency (p<0.01), and T-cell receptor excision circle levels in T_reg cells (p<0.01) were lower in CHF patients than in non-CHF controls. Combined annexin-V and 7-AAD staining showed that peripheral T_reg cells from CHF patients exhibited increased spontaneous apoptosis and were more prone to interleukin (IL)-2 deprivation- and CD95 ligand-mediated apoptosis than those from non-CHF individuals. Furthermore, analyses by both flow cytometry and real-time polymerase chain reaction showed that T_reg-cell frequency in the mediastinal lymph nodes or Foxp3 expression in hearts of CHF patients was no higher than that of the non-CHF controls.

Conclusion

Our data suggested that the T_reg-cell defects of CHF patients were likely caused by decreased thymic output of nascent T_reg cells and increased susceptibility to apoptosis in the periphery.     

Systemic BCG immunization induces persistent lung mucosal multifunctional CD4 T(EM) cells which expand following virulent mycobacterial challenge

To more closely understand the mechanisms of how BCG vaccination confers immunity would help to rationally design improved tuberculosis vaccines that are urgently required. Given the established central role of CD4 T cells in BCG induced immunity, we sought to characterise the generation of memory CD4 T cell responses to BCG vaccination and M. bovis infection in a murine challenge model. We demonstrate that a single systemic BCG vaccination induces distinct systemic and mucosal populations of T effector memory (T_EM) cells in vaccinated mice. These CD4⁺CD44^hiCD62L^loCD27⁻ T cells concomitantly produce IFN-γ and TNF-α, or IFN-γ, IL-2 and TNF-α and have a higher cytokine median fluorescence intensity MFI or ‘quality of response’ than single cytokine producing cells. These cells are maintained for long periods (>16 months) in BCG protected mice, maintaining a vaccine–specific functionality. Following virulent mycobacterial challenge, these cells underwent significant expansion in the lungs and are, therefore, strongly associated with protection against M. bovis challenge. Our data demonstrate that a persistent mucosal population of T_EM cells can be induced by parenteral immunization, a feature only previously associated with mucosal immunization routes; and that these multifunctional T_EM cells are strongly associated with protection. We propose that these cells mediate protective immunity, and that vaccines designed to increase the number of relevant antigen-specific T_EM in the lung may represent a new generation of TB vaccines.     

miR‐142‐3p restricts cAMP production in CD4+CD25− T cells and CD4+CD25+ TREG cells by targeting AC9 mRNA

Cyclic AMP (cAMP) is a ubiquitous second messenger that regulates diverse cellular functions. It has been found that CD4⁺CD25⁺ regulatory T (T_REG) cells exert their suppressor function by transferring cAMP to responder T cells. Here, we show that miR-142-3p regulates the production of cAMP by targeting adenylyl cyclase (AC) 9 messenger RNA in CD4⁺CD25⁻ T cells and CD4⁺CD25⁺ T_REG cells. miR-142-3p limits the level of cAMP in CD4⁺CD25⁻ T cells by inhibiting AC9 production, whereas forkhead box P3 (FOXP3) downregulates miR-142-3p to keep the AC9/cAMP pathway active in CD4⁺CD25⁺ T_REG cells. These findings reveal a new molecular mechanism through which CD4⁺CD25⁺ T_REG cells contain a high level of cAMP for their suppressor function, and also suggest that the microRNA controlling AC expression might restrict the final level of cAMP in various types of cells.     

BAFF promotes Th17 cells and aggravates experimental autoimmune encephalomyelitis

Background

BAFF, in addition to promoting B cell survival and differentiation, may affect T cells. The objective of this study was to determine the effect of BAFF on Th17 cell generation and its ramifications for the Th17 cell-driven disease, EAE.

Methodology/Principal Findings

Th17 cells were increased in BAFF-Tg B6 (B6.BTg) mice and decreased in B6.Baff^−/− mice. Th17 cells in B6.Baff^−/− mice bearing a BAFF Tg (B6.Baff^−/−.BTg mice) were identical to those in B6.BTg mice, indicating that membrane BAFF is dispensable for Th17 cell generation as long as soluble BAFF is plentiful. In T + non-T cell criss-cross co-cultures, Th17 cell generation was greatest in cultures containing B6.BTg T cells and lowest in cultures containing B6.Baff^−/− T cells, regardless of the source of non-T cells. In cultures containing only T cells, Th17 cell generation followed an identical pattern. CD4⁺ cell expression of CD126 (IL-6R α chain) was increased in B6.BTg mice and decreased in B6.Baff^−/− mice, and activation of STAT3 following stimulation with IL-6 + TGF-β was also greatest in B6.BTg cells and lowest in B6.Baff^−/− cells. EAE was clinically and pathologically most severe in B6.BTg mice and least severe in B6.Baff^−/− mice and correlated with MOG_35–55 peptide-induced Th17 cell responses.

Conclusions/Significance

Collectively, these findings document a contribution of BAFF to pathogenic Th17 cell responses and suggest that BAFF antagonism may be efficacious in Th17 cell-driven diseases.     

Deficient regulatory T cell activity and low frequency of IL-17-producing T cells correlate with the extent of cardiomyopathy in human Chagas' disease

Background

Myocardium damage during Chagas'' disease results from the immunological imbalance between pro- and production of anti-inflammatory cytokines and has been explained based on the Th1–Th2 dichotomy and regulatory T cell activity. Recently, we demonstrated that IL-17 produced during experimental T. cruzi infection regulates Th1 cells differentiation and parasite induced myocarditis. Here, we investigated the role of IL-17 and regulatory T cell during human Chagas'' disease.

Methodology/Principal Findings

First, we observed CD4⁺IL-17⁺ T cells in culture of peripheral blood mononuclear cells (PBMC) from Chagas'' disease patients and we evaluated Th1, Th2, Th17 cytokine profile production in the PBMC cells from Chagas'' disease patients (cardiomyopathy-free, and with mild, moderate or severe cardiomyopathy) cultured with T. cruzi antigen. Cultures of PBMC from patients with moderate and severe cardiomyopathy produced high levels of TNF-α, IFN-γ and low levels of IL-10, when compared to mild cardiomyopathy or cardiomyopathy-free patients. Flow cytometry analysis showed higher CD4⁺IL-17⁺ cells in PBMC cultured from patients without or with mild cardiomyopathy, in comparison to patients with moderate or severe cardiomyopathy. We then analyzed the presence and function of regulatory T cells in all patients. All groups of Chagas'' disease patients presented the same frequency of CD4⁺CD25⁺ regulatory T cells. However, CD4⁺CD25⁺ T cells from patients with mild cardiomyopathy or cardiomyopathy-free showed higher suppressive activity than those with moderate and severe cardiomyopathy. IFN-γ levels during chronic Chagas'' disease are inversely correlated to the LVEF (P = 0.007, r = −0.614), while regulatory T cell activity is directly correlated with LVEF (P = 0.022, r = 0.500).

Conclusion/Significance

These results indicate that reduced production of the cytokines IL-10 and IL-17 in association with high levels of IFN-γ and TNF-α is correlated with the severity of the Chagas'' disease cardiomyopathy, and the immunological imbalance observed may be causally related with deficient suppressor activity of regulatory T cells that controls myocardial inflammation.     

Direct Engagement of TLR4 in Invariant NKT Cells Regulates Immune Diseases by Differential IL-4 and IFN-γ Production in Mice

During interaction with APCs, invariant (i) NKT cells are thought to be indirectly activated by TLR4-dependently activated APCs. However, whether TLR4 directly activates iNKT cells is unknown. Therefore, the expression and function of TLR4 in iNKT cells were investigated. Flow cytometric and confocal microscopic analysis revealed TLR4 expression on the surface and in the endosome of iNKT cells. Upon LPS stimulation, iNKT cells enhanced IFN-γ production, but reduced IL-4 production, in the presence of TCR signals, depending on TLR4, MyD88, TRIF, and the endosome. However, enhanced TLR4-mediated IFN-γ production by iNKT cells did not affect IL-12 production or CD1d expression by DCs. Adoptive transfer of WT, but not TLR4-deficient, iNKT cells promoted antibody-induced arthritis in CD1d^−/− mice, suggesting that endogenous TLR4 ligands modulate iNKT cell function in arthritis. Furthermore, LPS-pretreated WT, but not TLR4-deficient, iNKT cells suppressed pulmonary fibrosis, but worsened hypersensitivity pneumonitis more than untreated WT iNKT cells, indicating that exogenous TLR4 ligands regulate iNKT cell functions in pulmonary diseases. Taken together, we propose a novel direct activation pathway of iNKT cells in the presence of TCR signals via endogenous or exogenous ligand-mediated engagement of TLR4 in iNKT cells, which regulates immune diseases by altering IFN-γ and IL-4 production.     

Serum amyloid A inhibits dendritic cell apoptosis to induce glucocorticoid resistance in CD4+ T cells

Mediators produced by the airway epithelium control the activation, recruitment, and survival of pulmonary dendritic cells (DC) that present antigen to CD4⁺ T cells during the genesis and exacerbation of allergic asthma. The epithelial-derived acute phase protein, serum amyloid A (SAA), induces DC maturation and T_H17 polarization. T_H17 responses are associated with severe forms of allergic asthma that are poorly controlled by corticosteroids. We sought to determine whether SAA would enhance the survival of DC during serum starvation and could then contribute to the development of a glucocorticoid-resistant phenotype in CD4⁺ T cells. Bone marrow-derived dendritic cells (BMDC) that were serum starved in the presence of SAA were protected from activation of caspase-3 and released less lactate dehydrogenase. In comparison with untreated serum-starved BMDC, treatment with SAA downregulated mRNA expression of the pro-apoptotic molecule Bim, increased production of the pro-survival heat shock protein 70 (HSP70), and induced secretion of pro-inflammatory cytokines. SAA-treated BMDC that were serum starved for 48 h remained capable of presenting antigen and induced OTII CD4⁺ T cells to secrete IL-17A, IL-17F, IL-21, IL-22, and IFNγ in the presence of ovalbumin. IL-17A, IL-17F, IL-21, and IFNγ production occurred even when the CD4⁺ T cells were treated with dexamethasone (Dex), whereas glucocorticoid treatment abolished cytokine secretion by T cells cocultured with untreated serum-starved BMDC. Measurement of Dex-responsive gene expression demonstrated CD4⁺ T cells as the target of glucocorticoid hyperresponsiveness manifest as a consequence of BMDC stimulation by SAA. Finally, allergic airway disease induced by SAA and antigen inhalation was unresponsive to Dex treatment. Our results indicate that apo-SAA affects DC to both prolong their viability and increase their inflammatory potential under apoptosis-inducing conditions. These findings reveal mechanisms through which SAA enhances the CD4⁺ T-cell-stimulating capacity of antigen-presenting cells that may actively participate in the pathogenicity of glucocorticoid-resistant lung disease.     

Nippostrongylus-Induced Intestinal Hypercontractility Requires IL-4 Receptor Alpha-Responsiveness by T Cells in Mice

Gut-dwelling helminthes induce potent IL-4 and IL-13 dominated type 2 T helper cell (T_H2) immune responses, with IL-13 production being essential for Nippostrongylus brasiliensis expulsion. This T_H2 response results in intestinal inflammation associated with local infiltration by T cells and macrophages. The resulting increased IL-4/IL-13 intestinal milieu drives goblet cell hyperplasia, alternative macrophage activation and smooth muscle cell hypercontraction. In this study we investigated how IL-4-promoted T cells contributed to the parasite induced effects in the intestine. This was achieved using pan T cell-specific IL-4 receptor alpha-deficient mice (iLck^creIL-4Rα^−/lox) and IL-4Rα-responsive control mice. Global IL-4Rα^−/− mice showed, as expected, impaired type 2 immunity to N. brasiliensis. Infected T cell-specific IL-4Rα-deficient mice showed comparable worm expulsion, goblet cell hyperplasia and IgE responses to control mice. However, impaired IL-4-promoted T_H2 cells in T cell-specific IL-4Rα deficient mice led to strikingly reduced IL-4 production by mesenteric lymph node CD4⁺ T cells and reduced intestinal IL-4 and IL-13 levels, compared to control mice. This reduced IL-4/IL-13 response was associated with an impaired IL-4/IL-13-mediated smooth muscle cell hypercontractility, similar to that seen in global IL-4Rα^−/− mice. These results demonstrate that IL-4-promoted T cell responses are not required for the resolution of a primary N. brasiliensis infection. However, they do contribute significantly to an important physiological manifestation of helminth infection; namely intestinal smooth muscle cell-driven hypercontractility.     

Local induction of immunosuppressive CD8+ T cells in the gut-associated lymphoid tissues

Background

In contrast to intestinal CD4⁺ regulatory T cells (T_regs), the generation and function of immunomodulatory intestinal CD8⁺ T cells is less well defined. To dissect the immunologic mechanisms of CD8⁺ T cell function in the mucosa, reactivity against hemagglutinin (HA) expressed in intestinal epithelial cells of mice bearing a MHC class-I-restricted T-cell-receptor specific for HA was studied.

Methodology and Principal Findings

HA-specific CD8⁺ T cells were isolated from gut-associated tissues and phenotypically and functionally characterized for the expression of Foxp3⁺ and their suppressive capacity. We demonstrate that intestinal HA expression led to peripheral induction of HA-specific CD8⁺Foxp3⁺ T cells. Antigen-experienced CD8⁺ T cells in this transgenic mouse model suppressed the proliferation of CD8⁺ and CD4⁺ T cells in vitro. Gene expression analysis of suppressive HA-specific CD8⁺ T cells revealed a specific up-regulation of CD103, Nrp1, Tnfrsf9 and Pdcd1, molecules also expressed on CD4⁺ T_reg subsets. Finally, gut-associated dendritic cells were able to induce HA-specific CD8⁺Foxp3⁺ T cells.

Conclusion and Significance

We demonstrate that gut specific antigen presentation is sufficient to induce CD8⁺ T_regs in vivo which may maintain intestinal homeostasis by down-modulating effector functions of T cells.     

1,25-Dihydroxyvitamin D3 inhibits the differentiation and migration of T(H)17 cells to protect against experimental autoimmune encephalomyelitis

Background

Vitamin D₃, the most physiologically relevant form of vitamin D, is an essential organic compound that has been shown to have a crucial effect on the immune responses. Vitamin D₃ ameliorates the onset of the experimental autoimmune encephalomyelitis (EAE); however, the direct effect of vitamin D₃ on T cells is largely unknown.

Methodology/Principal Findings

In an in vitro system using cells from mice, the active form of vitamin D₃ (1,25-dihydroxyvitamin D₃) suppresses both interleukin (IL)-17-producing T cells (T_H17) and regulatory T cells (Treg) differentiation via a vitamin D receptor signal. The ability of 1,25-dihydroxyvitamin D₃ (1,25(OH)₂D₃) to reduce the amount of IL-2 regulates the generation of Treg cells, but not T_H17 cells. Under T_H17-polarizing conditions, 1,25(OH)₂D₃ helps to increase the numbers of IL-10-producing T cells, but 1,25(OH)₂D₃''s negative regulation of T_H17 development is still defined in the IL-10^−/− T cells. Although the STAT1 signal reciprocally affects the secretion of IL-10 and IL-17, 1,25(OH)₂D₃ inhibits IL-17 production in STAT1^−/− T cells. Most interestingly, 1,25(OH)₂D₃ negatively regulates CCR6 expression which might be essential for T_H17 cells to enter the central nervous system and initiate EAE.

Conclusions/Significance

Our present results in an experimental murine model suggest that 1,25(OH)₂D₃ can directly regulate T cell differentiation and could be applied in preventive and therapeutic strategies for T_H17-mediated autoimmune diseases.     

Regulatory T cells in the pathogenesis and healing of chronic human dermal leishmaniasis caused by Leishmania (Viannia) species

Background

The inflammatory response is prominent in the pathogenesis of dermal leishmaniasis. We hypothesized that regulatory T cells (Tregs) may be diminished in chronic dermal leishmaniasis (CDL) and contribute to healing during treatment.

Methodology/Principal Findings

The frequency and functional capacity of Tregs were evaluated at diagnosis and following treatment of CDL patients having lesions of ≥6 months duration and asymptomatically infected residents of endemic foci. The frequency of CD4⁺CD25^hi cells expressing Foxp3 or GITR or lacking expression of CD127 in peripheral blood was determined by flow cytometry. The capacity of CD4⁺CD25⁺ cells to inhibit Leishmania-specific responses was determined by co-culture with effector CD4⁺CD25⁻ cells. The expression of FOXP3, IFNG, IL10 and IDO was determined in lesion and leishmanin skin test site biopsies by qRT-PCR. Although CDL patients presented higher frequency of CD4⁺CD25^hiFoxp3⁺ cells in peripheral blood and higher expression of FOXP3 at leishmanin skin test sites, their CD4⁺CD25⁺ cells were significantly less capable of suppressing antigen specific-IFN-γ secretion by effector cells compared with asymptomatically infected individuals. At the end of treatment, both the frequency of CD4⁺CD25^hiCD127⁻ cells and their capacity to inhibit proliferation and IFN-γ secretion increased and coincided with healing of cutaneous lesions. IDO was downregulated during healing of lesions and its expression was positively correlated with IFNG but not FOXP3.

Conclusions/Significance

The disparity between CD25^hiFoxp3⁺ CD4 T cell frequency in peripheral blood, Foxp3 expression at the site of cutaneous responses to leishmanin, and suppressive capacity provides evidence of impaired Treg function in the pathogenesis of CDL. Moreover, the concurrence of increased Leishmania-specific suppressive capacity with induction of a CD25^hiCD127⁻ subset of CD4 T cells during healing supports the participation of Tregs in the resolution of chronic dermal lesions. Treg subsets may therefore be relevant in designing immunotherapeutic strategies for recalcitrant dermal leishmaniasis caused by Leishmania (Viannia) species.     

Assessing the role of CD103 in immunity to an intestinal helminth parasite

Background

In the intestine, the integrin CD103 is expressed on a subset of T regulatory (T_reg) cells and a population of dendritic cells (DCs) that produce retinoic acid and promote immune homeostasis. However, the role of CD103 during intestinal helminth infection has not been tested.

Methodology/Principal Findings

We demonstrate that CD103 is dispensable for the development of protective immunity to the helminth parasite Trichuris muris. While we observed an increase in the frequency of CD103⁺ DCs in the lamina propria (LP) following acute high-dose infection with Trichuris, lack of CD103 had no effect on the frequency of CD11c⁺ DCs in the LP or mesenteric lymph nodes (mLN). CD103-deficient (CD103^−/−) mice develop a slightly increased and earlier T cell response but resolve infection with similar kinetics to control mice. Similarly, low-dose chronic infection of CD103^−/− mice with Trichuris resulted in no significant difference in immunity or parasite burden. Absence of CD103 also had no effect on the frequency of CD4⁺CD25⁺Foxp3⁺ T_reg cells in the mLN or LP.

Conclusions/Significance

These results suggest that CD103 is dispensable for intestinal immunity during helminth infection. Furthermore, lack of CD103 had no effect on DC or T_reg recruitment or retention within the large intestine.     

IL-17A expression is localised to both mononuclear and polymorphonuclear synovial cell infiltrates

Introduction

This study examines the expression of IL-17A-secreting cells within the inflamed synovium and the relationship to in vivo joint hypoxia measurements.

Methods

IL-17A expression was quantified in synovial tissue (ST), serum and synovial fluid (SF) by immunohistochemistry and MSD-plex assays. IL-6 SF and serum levels were measured by MSD-plex assays. Dual immunofluorescence for IL-17A was quantified in ST CD15+ cells (neutrophils), Tryptase+ (mast cells) and CD4+ (T cells). Synovial tissue oxygen (tpO₂) levels were measured under direct visualisation at arthroscopy. Synovial infiltration was assessed using immunohistochemistry for cell specific markers. Peripheral blood mononuclear and polymorphonuclear cells were isolated and exposed to normoxic or 3% hypoxic conditions. IL-17A and IL-6 were quantified as above in culture supernatants.

Results

IL-17A expression was localised to mononuclear and polymorphonuclear (PMN) cells in inflamed ST. Dual immunoflourescent staining co-localised IL-17A expression with CD15+ neutrophils Tryptase+ mast cells and CD4+T cells. % IL-17A positivity was highest on CD15+ neutrophils, followed by mast cells and then CD4+T-cells. The number of IL-17A-secreting PMN cells significantly correlated with sublining CD68 expression (r = 0.618, p<0.01). IL-17A SF levels correlated with IL-6 SF levels (r = 0.675, p<0.01). Patients categorized according to tp0₂< or >20mmHg, showed those with low tp0₂<20mmHg had significantly higher IL-17A+ mononuclear cells with no difference observed for PMNs. Exposure of mononuclear and polymorphonuclear cells to 3% hypoxia, significantly induced IL-6 in mononuclear cells, but had no effect on IL-17A expression in mononuclear and polymorphonuclear cells.

Conclusion

This study demonstrates IL-17A expression is localised to several immune cell subtypes within the inflamed synovial tissue, further supporting the concept that IL-17A is a key mediator in inflammatory arthritis. The association of hypoxia with Il-17A expression appears to be indirect, probably through hypoxia-induced pro-inflammatory pathways and leukocyte influx within the joint microenvironment.     

Non-classical Natural Killer T Cells Modulate Plasmid DNA Vaccine Antigen Expression and Vaccine-elicited Immune Responses by MCP-1 Secretion after Interaction with a ��2-Microglobulin-independent CD1d

The magnitude and durability of a plasmid DNA vaccine-induced immune response is shaped by immune effector molecules at the site of vaccination. In the present study, we show that antigen expression is modified by type II NKT cells, after interaction with a β2-microglobulin-independent CD1d receptor. After activation, during the first days following plasmid DNA vaccination, NKT cells release IL-5 and MCP-1, leading to a T helper 0 (T_H0) cytokine/chemokine profile and a stronger CD8⁺/CD4⁺ T cell immune response. Our data indicate that this phenomenon was induced through the strong T_H1 chemokine MCP-1 during the early phases of plasmid DNA vaccination because injecting the type II NKT cell-associated MCP-1 during the first 5 days led to 2–3-fold increases in vaccine-elicited T cell responses. This study demonstrates a critical role for NKT cells in plasmid DNA vaccine-induced immune responses. Manipulation of NKT cell function or co-administration of MCP-1 may represent novel methods for enhancing immune responses to plasmid DNA vaccines.     

Differential expression of NK receptors CD94 and NKG2A by T cells in rheumatoid arthritis patients in remission compared to active disease

Objective

TNF inhibitors (TNFi) have revolutionised the treatment of rheumatoid arthritis (RA). Natural killer (NK) cells and Natural Killer Cell Receptor⁺ T (NKT) cells comprise important effector lymphocytes whose activity is tightly regulated through surface NK receptors (NKRs). Dysregulation of NKRs in patients with autoimmune diseases has been shown, however little is known regarding NKRs expression in patients with TNFi-induced remission and in those who maintain remission vs disease flare following TNFi withdrawal.

Methods

Patients with RA were recruited for this study, (i) RA patients in clinical remission following a minimum of one year of TNFi therapy (n = −15); (2) Active RA patients, not currently or ever receiving TNFi (n = 18); and healthy control volunteers (n = 15). Patients in remission were divided into two groups: those who were maintained on TNFi and those who withdrew from TNFi and maintained on DMARDS. All patients underwent full clinical assessment. Peripheral blood mononuclear cells were isolated and NKR (CD94, NKG2A, CD161, CD69, CD57, CD158a, CD158b) expression on T-(CD3⁺CD56⁻), NK-(CD3⁻CD56⁺) and NKT-(CD3⁺CD56⁺) cells was determined by flow cytometry.

Results

Following TNFi withdrawal, percentages and numbers of circulating T cells, NK cells or NKT cell populations were unchanged in patients in remission versus active RA or HCs. Expression of the NKRs CD161, CD57, CD94 and NKG2A was significantly increased on CD3⁺CD56-T cells from patients in remission compared to active RA (p<0.05). CD3⁺CD56-T cell expression of CD94 and NKG2A was significantly increased in patients who remained in remission compared with patients whose disease flared (p<0.05), with no differences observed for CD161 and CD57. CD3⁺CD56⁻ cell expression of NKG2A was inversely related to DAS28 (r = −0.612, p<0.005).

Conclusion

High CD94/NKG2A expression by T cells was demonstrated in remission patients following TNFi therapy compared to active RA, while low CD94/NKG2A were associated with disease flare following withdrawal of therapy.     

Association of differentiation state of CD4+ T cells and disease progression in HIV-1 perinatally infected children

Background

In the USA, most HIV-1 infected children are on antiretroviral drug regimens, with many individuals surviving through adolescence and into adulthood. The course of HIV-1 infection in these children is variable, and understudied.

Methodology/Principal Findings

We determined whether qualitative differences in immune cell subsets could explain a slower disease course in long term survivors with no evidence of immune suppression (LTS-NS; CD4%≥25%) compared to those with severe immune suppression (LTS-SS; CD4%≤15%). Subjects in the LTS-NS group had significantly higher frequencies of naïve (CCR7+CD45RA+) and central memory (CCR7+CD45RA−) CD4+ T cells compared to LTS-SS subjects (p = 0.0005 and <0.0001, respectively). Subjects in the rapid progressing group had significantly higher levels of CD4+ T_EMRA (CCR7−CD45RA+) cells compared to slow progressing subjects (p<0.0001).

Conclusions/Significance

Rapid disease progression in vertical infection is associated with significantly higher levels of CD4+ T_EMRA (CCR7−CD45RA+) cells.     

The Retinoic Acid-Metabolizing Enzyme Cyp26b1 Regulates CD4 T Cell Differentiation and Function

The vitamin A metabolite retinoic acid (RA) has potent immunomodulatory properties that affect T cell differentiation, migration and function. However, the precise role of RA metabolism in T cells remains unclear. Catabolism of RA is mediated by the Cyp26 family of cytochrome P450 oxidases. We examined the role of Cyp26b1, the T cell-specific family member, in CD4⁺ T cells. Mice with a conditional knockout of Cyp26b1 in T cells (Cyp26b1 ^−/− mice) displayed normal lymphoid development but showed an increased sensitivity to serum retinoids, which led to increased differentiation under both inducible regulatory T (iT_reg) cell- and T_H17 cell-polarizing conditions in vitro. Further, Cyp26b1 expression was differentially regulated in iT_reg and T_H17 cells. Transfer of naïve Cyp26b1 ^−/− CD4⁺ T cells into Rag1 ^−/− mice resulted in significantly reduced disease in a model of T cell-dependent colitis. Our results show that T cell-specific expression of Cyp26b1 is required for the development of T cell-mediated colitis and may be applicable to the development of therapeutics that target Cyp26b1 for the treatment of inflammatory bowel disease.