Could a loss of memory T cells limit responses to hepatitis C virus (HCV) antigens in blood leucocytes from patients chronically infected with HCV before and during pegylated interferon-α and ribavirin therapy?

The proportions and activation status of T cells may influence responses to hepatitis C virus (HCV) and treatment outcome in patients receiving pegylated interferon (IFN)‐α/ribavirin therapy. We confirmed that IFN‐γ enzyme‐linked immunospot (ELISPOT) responses to HCV are poor in HCV patients and showed that responses to HCV and cytomegalovirus (CMV) antigens decrease during therapy. This was most apparent in patients with sustained virological response (SVR). Baseline frequencies of CD4⁺ effector memory (T_EM) T cells were lower in SVR than non‐SVR. Proportions of CD4⁺ and CD8⁺ T_EM and terminally differentiated effector memory (T_EMRA) T cells declined on therapy in SVR, as did proportions of Fas⁺ CD8⁺ T_EMRA T cells. Baseline frequencies of programmed death (PD)‐1‐expressing CD4⁺ T_EM and T_EMRA T‐cells were higher in SVR. Therapy increased percentages of PD‐1⁺ CD4⁺ central memory (T_CM) T cells and PD‐1⁺ CD8⁺ T_EM and T_EMRA T cells in SVR. We conclude that successful therapy depletes circulating antigen‐specific CD4⁺ T cell responses. This paralleled decreases in proportions of effector memory T cells and higher percentages of CD4⁺ T_CM T cells expressing PD‐1.     

Asymptomatic CMV infections in long‐term renal transplant recipients are associated with the loss of FcRγ from LIR‐1+ NK cells

While it is established that cytomegalovirus (CMV) disease affects NK‐cell profiles, the functional consequences of asymptomatic CMV replication are unclear. Here, we characterize NK cells in clinically stable renal transplant recipients (RTRs; n = 48) >2 years after transplantation. RTRs and age‐matched controls (n = 32) were stratified by their CMV serostatus and the presence of measurable CMV DNA. CMV antibody or CMV DNA influenced expression of NKG2C, LIR‐1, NKp30, NKp46, and FcRγ, a signaling adaptor molecule, on CD56^dim NK cells. Phenotypic changes ascribed to CMV were clearer in RTRs than in control subjects and affected NK‐cell function as assessed by TNF‐α and CD107a expression. The most active NK cells were FcRγ^–LIR‐1⁺NKG2C^– and displayed high antibody‐dependent cell cytotoxicity responses in the presence of immobilized CMV glycoprotein B reactive antibody. However, perforin levels in supernatants from RTRs with active CMV replication were low. Overall we demonstrate that CMV can be reactivated in symptom‐free renal transplant recipients, affecting the phenotypic, and functional profiles of NK cells. Continuous exposure to CMV may maintain and expand NK cells that lack FcRγ but express LIR‐1.     

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.     

Mycobacterium tuberculosis‐specific CD8+ T cells are functionally and phenotypically different between latent infection and active disease

Protective immunity to Mycobacterium tuberculosis (Mtb) remains poorly understood and the role of Mtb‐specific CD8⁺ T cells is controversial. Here we performed a broad phenotypic and functional characterization of Mtb‐specific CD8⁺ T cells in 326 subjects with latent Mtb infection (LTBI) or active TB disease (TB). Mtb‐specific CD8⁺ T cells were detected in most (60%) TB patients and few (15%) LTBI subjects but were of similar magnitude. Mtb‐specific CD8⁺ T cells in LTBI subjects were mostly T_EMRA cells (CD45RA⁺CCR7^?), coexpressing 2B4 and CD160, and in TB patients were mostly T_EM cells (CD45RA^?CCR7^?), expressing 2B4 but lacking PD‐1 and CD160. The cytokine profile was not significantly different in both groups. Furthermore, Mtb‐specific CD8⁺ T cells expressed low levels of perforin and granulysin but contained granzymes A and B. However, in vitro‐expanded Mtb‐specific CD8⁺ T cells expressed perforin and granulysin. Finally, Mtb‐specific CD8⁺ T‐cell responses were less frequently detected in extrapulmonary TB compared with pulmonary TB patients. Mtb‐specific CD8⁺ T‐cell proliferation was also greater in patients with extrapulmonary compared with pulmonary TB. Thus, the activity of Mtb infection and clinical presentation are associated with distinct profiles of Mtb‐specific CD8⁺ T‐cell responses. These results provide new insights in the interaction between Mtb and the host immune response.     

Generation of specific effector and memory T cells with gut- and secondary lymphoid tissue- homing potential by oral attenuated CVD 909 typhoid vaccine in humans

Induction of effective memory T cells is likely to be critical to the level and duration of protection elicited by novel live oral typhoid vaccines. Using cells from volunteers who ingested Salmonella Typhi vaccine strain CVD 909, we characterized the induction of interferon (IFN)-γ-secreting central (T_CM, CD45RO⁺CD62L⁺) and effector (T_EM, CD45RO⁺CD62L⁻) memory T populations, and their gut-homing potential based on integrin α4/β7 expression. Both CD4⁺ T_EM and T_CM populations secreted IFN-γ. However, although CD4⁺ T_EM expressed, or not, integrin α₄/β₇, CD4⁺ T_CM cells were predominantly integrin α₄/β₇⁺. In contrast, IFN-γ-secreting CD8⁺ cells were predominantly classical T_EM and CD45RA⁺ T_EM (T_EMRA, CD45RO⁻CD62L⁻) subsets. However, although CD8⁺ T_EM expressed, or not, integrin α₄/β₇, CD8⁺ T_EMRA were predominantly integrin α₄/β₇⁺. This is the first demonstration that oral immunization of humans with S. Typhi elicits diverse IFN-γ-secreting CD4⁺ and CD8⁺ T_CM and T_EM subsets able to migrate to the gut and other lymphoid tissues.     

CD4+ CD25+ Treg regulate the contribution of CD8+ T-cell subsets in repopulation of the lymphopenic environment

Peripheral T‐cell expansion is of major relevance for immune function after lymphopenia. In order to promote regeneration, the process should result in a peripheral T‐cell pool with a similar subpopulation structure as before lymphopenia. We investigated the repopulation of the CD8⁺ central‐memory T cells (T_CM) and effector‐memory T cells (T_EM) pools after adoptive transfer of sorted CD8⁺ T cells from naïve, T_CM and T_EM subsets into T‐cell‐deficient hosts. We show that the initial kinetics of expansion are distinct for each subset and that the contribution to the repopulation of the CD8⁺ T‐cell pool by the progeny of each subset is not a mere function of its initial expansion. We demonstrate that CD4⁺CD25⁺ Treg play a major role in the repopulation of the CD8⁺ T‐cell pool and that CD8⁺ T‐cell subsets impact on each other. In the absence of CD4⁺CD25⁺ Treg, a small fraction of naïve CD8⁺ T cells strongly proliferates, correlating with further expansion and differentiation of co‐expanding CD8⁺ T cells. CD4⁺CD25⁺ Treg suppress these responses and lead to controlled repopulation, contributing decisively to the maintenance of recovered T_CM and T_EM fractions, and leading to repopulation of each pool with progeny of its own kind.     

Antigen presentation by B cells guides programing of memory CD4+ T‐cell responses to a TLR4‐agonist containing vaccine in mice

The contribution of B cells to immunity against many infectious diseases is unquestionably important and well characterized. Here, we sought to determine the role of B cells in the induction of T‐helper 1 (T_H1) CD4⁺ T cells upon vaccination with a tuberculosis (TB) antigen combined with a TLR4 agonist. We used B‐cell deficient mice (μMT^?/?), tetramer‐positive CD4⁺ T cells, markers of memory “precursor” effector cells (MPECs), and T‐cell adoptive transfers and demonstrated that the early antigen‐specific cytokine‐producing T_H1 responses are unaffected in the absence of B cells, however MPEC induction is strongly impaired resulting in a deficiency of the memory T_H1 response in μMT^?/? mice. We further show that antigen‐presentation by B cells is necessary for their role in MPEC generation using B‐cell adoptive transfers from wt or MHC class II knock‐out mice into μMT^?/? mice. Our study challenges the view that B‐cell deficiency exclusively alters the T_H1 response at memory time‐points. Collectively, our results provide new insights on the multifaceted roles of B cells that will have a high impact on vaccine development against several pathogens including those requiring T_H1 cell‐mediated immunity.     

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.     

Differential Sensitivity of Naïve and Memory Subsets of Human CD8+ T Cells to TNF-α-Induced Apoptosis

In this investigation, we have examined the relative sensitivity of human naïve, central memory (T_CM), and two types of effector memory CD8+ T cells (T_EM and T_EMRA) to TNF-α-induced apoptosis. Our data show that naïve and T_CM CD8+ T cells were sensitive, whereas T_EM and T_EMRA CD8+ T cells were relatively resistant to TNF-a-induced apoptosis. The apoptosis profile correlated with the activation of caspase-8 and caspase-3. However, no correlation was observed between relative sensitivity of four CD8 + T cell subsets to apoptosis and the expression of TNFR-I or TNFR-II. T_EM and T_EMRA CD8+ T cells displayed increased phosphorylation of IKKα/β and IκB and increased NF-κB activity as compared to naïve and T_CM CD8+ T cells. Bcl-2, Bcl-x_L and FLIP_L expression was higher and Bax expression was lower in T_EM and T_EMRA CD8+ T cells as compared to naïve and T_CM CD8+ T cells. These data suggest that signaling molecules downstream of TNFRs may be responsible for differential sensitivity among subsets of CD8+ T cells to TNF-α-induced apoptosis.     

Coordinated expansion of both memory T cells and NK cells in response to CMV infection in humans

NK cells are key players in the fight against persistent viruses. Human cytomegalovirus (HCMV) infection is associated with the presence of a population of CD16⁺ CD56^dim NKG2C⁺ NK cells in both acutely and latently infected individuals. Here, we studied the nature of these terminally differentiated NK cells in different human populations infected with HCMV: healthy donors stratified by age, thymectomized individuals, pregnant women suffering from primary CMV infection, and lung transplant patients. Both CD16⁺ CD56^dim NK‐ and CD8 T‐cell phenotypes as well as functional capacities were determined and stratified according to age and/or CMV event. Similarly to T‐cell responsiveness, we observe an accumulation over time of NKG2C⁺ NK cells, which preferentially expressed CD57. This accumulation is particularly prominent in elderly and amplified further by CMV infection. Latent HCMV infection (without replication) is sufficient for NKG2C⁺ CD57⁺ NK cells to persist in healthy individuals but is not necessarily required in old age. Collectively, the present work supports the emerging concept that CMV shapes both innate and adaptive immunity in humans.     

Circulating memory CD8+ T cells are limited in forming CD103+ tissue-resident memory T cells at mucosal sites after reinfection

Tissue-resident memory CD8⁺ T cells (T_RM) localize to barrier tissues and mediate local protection against reinvading pathogens. Circulating central memory (T_CM) and effector memory CD8⁺ T cells (T_EM) also contribute to tissue recall responses, but their potential to form mucosal T_RM remains unclear. Here, we employed adoptive transfer and lymphocytic choriomeningitis virus reinfection models to specifically assess secondary responses of T_CM and T_EM at mucosal sites. Donor T_CM and T_EM exhibited robust systemic recall responses, but only limited accumulation in the small intestine, consistent with reduced expression of tissue-homing and -retention molecules. Murine and human circulating memory T cells also exhibited limited CD103 upregulation following TGF-β stimulation. Upon pathogen clearance, T_CM and T_EM readily gave rise to secondary T_EM. T_CM also formed secondary central memory in lymphoid tissues and T_RM in internal tissues, for example, the liver. Both T_CM and T_EM failed to substantially contribute to resident mucosal memory in the small intestine, while activated intestinal T_RM, but not liver T_RM, efficiently reformed CD103⁺ T_RM. Our findings demonstrate that circulating T_CM and T_EM are limited in generating mucosal T_RM upon reinfection. This may pose important implications on cell therapy and vaccination strategies employing memory CD8⁺ T cells for protection at mucosal sites.     

The generation of human innate lymphoid cells is influenced by the source of hematopoietic stem cells and by the use of G‐CSF

NK cells play a central role in the haploidentical HSC transplantation (HSCT) to cure high‐risk leukemias. Other innate lymphoid cells (ILCs) have been proposed to exert a protective role in graft‐versus‐host disease and could also contribute to anti‐microbial defence and to lymphoid tissue remodeling. Thus, we investigated the ILC differentiation potential of HSCs isolated from BM, mobilized peripheral blood (PB), and umbilical cord blood (UCB). BM CD34⁺ cells are enriched in lymphoid‐committed precursors, while PB CD34⁺ cells preferentially contain myeloid precursors. In vitro differentiation experiments revealed that the highest and the lowest CD56⁺CD161⁺ ILC recovery was detected in UCB and PB HSC cultures, respectively. Among CD56⁺CD161⁺ ILCs, the ratio between NK cells and ILC3s was similar for all HSC analyzed. ILC recovery in PB CD34⁺ cultures was lower for G‐CSF‐mobilized HSCs (good mobilizers) than for G‐CSF+plerixafor‐mobilized HSC (poor mobilizers). Moreover, G‐CSF inhibited in vitro ILC recovery and the degree of inhibition was proportional to the time of exposure to the cytokine. Thus, although all common sources of HSC for transplant differentiate towards ILCs, substantial differences exist among different sources and G‐CSF may influence ILC recovery. These data offer new clues for a better understanding of the immune reconstitution after HSCT.     

Mouse pancreatic beta cells express MHC class II and stimulate CD4+ T cells to proliferate

Type 1 diabetes results from destruction of pancreatic beta cells by autoreactive T cells. Both CD4⁺ and CD8⁺ T cells have been shown to mediate beta‐cell killing. While CD8⁺ T cells can directly recognize MHC class I on beta cells, the interaction between CD4⁺ T cells and beta cells remains unclear. Genetic association studies have strongly implicated HLA‐DQ alleles in human type 1 diabetes. Here we studied MHC class II expression on beta cells in nonobese diabetic mice that were induced to develop diabetes by diabetogenic CD4⁺ T cells with T‐cell receptors that recognize beta‐cell antigens. Acute infiltration of CD4⁺ T cells in islets occurred with rapid onset of diabetes. Beta cells from islets with immune infiltration expressed MHC class II mRNA and protein. Exposure of beta cells to IFN‐γ increased MHC class II gene expression, and blocking IFN‐γ signaling in beta cells inhibited MHC class II upregulation. IFN‐γ also increased HLA‐DR expression in human islets. MHC class II⁺ beta cells stimulated the proliferation of beta‐cell‐specific CD4⁺ T cells. Our study indicates that MHC class II molecules may play an important role in beta‐cell interaction with CD4⁺ T cells in the development of type 1 diabetes.     

Donor bone marrow cells are essential for iNKT cell‐mediated Foxp3+ Treg cell expansion in a murine model of transplantation tolerance

Mixed chimerism induction is the most reliable method for establishing transplantation tolerance. We previously described a novel treatment using a suboptimal dose of anti‐CD40 ligand (anti‐CD40L) and liposomal formulation of a ligand for invariant natural killer T cells administered to sub‐lethally irradiated recipient mice after donor bone marrow cell (BMC) transfer. Recipient mice treated with this regimen showed expansion of a Foxp3‐positive regulatory T(Treg) cell phenotype, and formation of mixed chimera. However, the mechanism of expansion and bioactivity of Treg cells remains unclear. Here, we examine the role of donor BMCs in the expansion of bioactive Treg cells. The mouse model was transplanted with a heart allograft the day after treatment. The results showed that transfer of spleen cells in place of BMCs failed to deplete host interferon (IFN)‐γ‐producing CD8⁺T cells, expand host Ki67⁺CD4⁺CD25⁺Foxp3⁺ Treg cells, and prolong graft survival. Severe combined immunodeficiency mice who received Treg cells obtained from BMC‐recipients accepted skin grafts in an allo‐specific manner. Myeloid‐derived suppressor cells, which were a copious cell subset in BMCs, enhanced the Ki67 expression of Treg cells. This suggests that donor BMCs are indispensable for the expansion of host bioactive Treg cells in our novel treatment for transplant tolerance induction.     

Immunosuppressive evidence of Tityus serrulatus toxins Ts6 and Ts15: insights of a novel K+ channel pattern in T cells

The voltage‐gated potassium channel Kv1.3 is a novel target for immunomodulation of autoreactive effector memory T cells, which play a major role in the pathogenesis of autoimmune diseases. In this study, the Ts6 and Ts15 toxins isolated from Tityus serrulatus (Ts) were investigated for their immunosuppressant roles on CD4⁺ cell subsets: naive, effector (T_EF), central memory (T_CM) and effector memory (T_EM). The electrophysiological assays confirmed that both toxins were able to block Kv1.3 channels. Interestingly, an extended Kv channel screening shows that Ts15 blocks Kv2.1 channels. Ts6 and Ts15 significantly inhibit the proliferation of T_EM cells and interferon‐γ production; however, Ts15 also inhibits other CD4⁺ cell subsets (naive, T_EF and T_CM). Based on the Ts15 inhibitory effect of proliferation of all CD4⁺ cell subsets, and based on its blocking effect on Kv2.1, we investigated the Kv2.1 expression in T cells. The assays showed that CD4⁺ and CD8⁺ cells express the Kv2.1 channels mainly extracellularly with T_CM cells expressing the highest number of Kv2.1 channels. We also provide in vivo experimental evidence to the protective effect of Ts6 and Ts15 on delayed‐type hypersensitivity reaction. Altogether, this study presents the immunosuppressive behaviour of Ts6 and Ts15 toxins, indicating that these toxins could be promising candidates for autoimmune disease therapy. Moreover, this is the first report illustrating the involvement of a novel K⁺ channel subtype, Kv2.1, and its distribution in T‐cell subsets.     

OX40 and IL‐7 play synergistic roles in the homeostatic proliferation of effector memory CD4+ T cells

T‐cell homeostasis preserves the numbers, the diversity and functional competence of different T‐cell subsets that are required for adaptive immunity. Naïve CD4⁺ T (T_N) cells are maintained in the periphery via the common γ‐chain family cytokine IL‐7 and weak antigenic signals. However, it is not clear how memory CD4⁺ T‐cell subsets are maintained in the periphery and which factors are responsible for the maintenance. To examine the homeostatic mechanisms, CFSE‐labeled CD4⁺CD44^highCD62L^low effector memory T (T_EM) cells were transferred into sublethally‐irradiated syngeneic C57BL/6 mice, and the systemic cell proliferative responses, which can be divided distinctively into fast and slow proliferations, were assessed by CFSE dye dilution. We found that the fast homeostatic proliferation of T_EM cells was strictly regulated by both antigen and OX40 costimulatory signals and that the slow proliferation was dependent on IL‐7. The simultaneous blockade of both OX40 and IL‐7 signaling completely inhibited the both fast and slow proliferation. The antigen‐ and OX40‐dependent fast proliferation preferentially expanded IL‐17‐producing helper T cells (Th17 cells). Thus, OX40 and IL‐7 play synergistic, but distinct roles in the homeostatic proliferation of CD4⁺ T_EM cells.     

Combination of pegylated interferon-alpha and nucleos(t)ide analogue treatment enhances the activity of natural killer cells in nucleos(t)ide analogue experienced chronic hepatitis B patients

A combination of pegylated interferon-alpha (peg-IFN-α) and nucleos(t)ides analogue (NA) therapy can effectively reduce hepatitis B surface antigen (HBsAg), especially in NA-experienced chronic hepatitis B (CHB) patients. However, the immune mechanism of this therapy is unclear. Forty NA-experienced CHB patients were enrolled into this study. The frequencies of peripheral blood natural killer (NK) cells, dendritic cells (DCs), CD4⁺ T cells, CD8⁺ T cells, T helper (Th) cells, regulatory T cells (T_reg), B cells and follicular T helper (Tfh) cells were evaluated by flow cytometry. Seven of the 40 patients converted to peg-IFN-α combined with NA treatment, while the other 33 continued to NA therapy. The decrease in HBsAg was more pronounced in the combination treatment group, and only patients receiving combination treatment achieved HBsAg loss. The frequency and absolute number of CD56^bright NK cells in the combination treatment group increased significantly compared with the NA treatment group, whereas the CD56^dim NK cells were decreased. In the NA treatment group, the proportions of CD4⁺ T_N, CD8⁺ T_N, CD19⁺ B and cytotoxic T lymphocyte antigen-4 (CTLA-4)⁺CD4⁺ T cells were increased, while the proportions of CD4⁺ T_EM, CD8⁺ T_EM, CD25⁺CD4⁺ T_reg, CD25^highCD4⁺ T_reg, CD127^lowCD25⁺ T_reg, programmed cell death 1 (PD-1)⁺CD4⁺ T, PD-1⁺CD8⁺ T, CTLA-4⁺CD8⁺ T, CCR4⁺CD25⁺ T_reg and CCR4⁺CD25^high T_reg cells were decreased after therapy. For NA-experienced CHB patients who achieved low HBsAg levels, combination treatment is more likely to result in HBsAg decline and HBsAg clearance by increasing the activity of CD56^brightNK cells.     

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.     

Depletion of CD4+CD25+ regulatory T cells enhances natural killer T cell‐mediated anti‐tumour immunity in a murine mammary breast cancer model

Both invariant natural killer T (NK T) cells and CD4⁺CD25⁺ T regulatory cells (T_regs) regulate the immune system to maintain homeostasis. In a tumour setting, NK T cells activated by α‐galactosylceramide (α‐GalCer) execute anti‐tumour activity by secreting cytokines. By contrast, T_regs intrinsically suppress antigen‐specific immune responses and are often found to be elevated in tumour patients. In this study, we have shown that T_regs regulate NK T cell function negatively in vitro, suggesting a direct interaction between these cell types. In a murine mammary tumour model, we demonstrated that administration of either α‐GalCer or anti‐CD25 antibody alone markedly suppressed tumour formation and pulmonary metastasis, and resulted in an increase in the survival rate up to 44% (from a baseline of 0%). When treatments were combined, depletion of T_regs boosted the anti‐tumour effect of α‐GalCer, and the survival rate jumped to 85%. Our results imply a potential application of combining T_reg cell depletion with α‐GalCer to stimulate NK T cells for cancer therapy.     

Cell surface levels of endothelial ICAM‐1 influence the transcellular or paracellular T‐cell diapedesis across the blood–brain barrier

The extravasation of CD4⁺ effector/memory T cells (T_EM cells) across the blood–brain barrier (BBB) is a crucial step in the pathogenesis of experimental autoimmune encephalomyelitis (EAE) or multiple sclerosis (MS). Endothelial ICAM‐1 and ICAM‐2 are essential for CD4⁺ T_EM cell crawling on the BBB prior to diapedesis. Here, we investigated the influence of cell surface levels of endothelial ICAM‐1 in determining the cellular route of CD4⁺ T_EM‐cell diapedesis across cytokine treated primary mouse BBB endothelial cells under physiological flow. Inflammatory conditions, inducing high levels of endothelial ICAM‐1, promoted rapid initiation of transcellular diapedesis of CD4⁺ T cells across the BBB, while intermediate levels of endothelial ICAM‐1 favored paracellular CD4⁺ T‐cell diapedesis. Importantly, the route of T‐cell diapedesis across the BBB was independent of loss of BBB barrier properties. Unexpectedly, a low number of CD4⁺ T_EM cells was found to cross the inflamed BBB in the absence of endothelial ICAM‐1 and ICAM‐2 via an obviously alternatively regulated transcellular pathway. In vivo, this translated to the development of ameliorated EAE in ICAM‐1^null//ICAM‐2^?/?C57BL/6J mice. Taken together, our study demonstrates that cell surface levels of endothelial ICAM‐1 rather than the inflammatory stimulus or BBB integrity influence the pathway of T‐cell diapedesis across the BBB.