Selective infection of CD4 effector memory T lymphocytes leads to preferential depletion of memory T lymphocytes in R5 HIV-1-infected humanized NOD/SCID/IL-2Rγ mice

To investigate the events leading to the depletion of CD4⁺ T lymphocytes during long-term infection of human immunodeficiency virus type 1 (HIV-1), we infected human CD34⁺ cells-transplanted NOD/SCID/IL-2Rγ^null mice with CXCR4-tropic and CCR5-tropic HIV-1. CXCR4-tropic HIV-1-infected mice were quickly depleted of CD4⁺ thymocytes and both CD45RA⁺ naïve and CD45RA⁻ memory CD4⁺ T lymphocytes, while CCR5-tropic HIV-1-infected mice were preferentially depleted of CD45RA⁻ memory CD4⁺ T lymphocytes. Staining of HIV-1 p24 antigen revealed that CCR5-tropic HIV-1 preferentially infected effector memory T lymphocytes (T_EM) rather than central memory T lymphocytes. In addition, the majority of p24⁺ cells in CCR5-tropic HIV-1-infected mice were activated and in cycling phase. Taken together, our findings indicate that productive infection mainly takes place in the activated T_EM in cycling phase and further suggest that the predominant infection in T_EM would lead to the depletion of memory CD4⁺ T lymphocytes in CCR5-tropic HIV-1-infected mice.     

Human natural killer (NK) cells present staphylococcal enterotoxin B (SEB) to T lymphocytes

Superantigen-mediated T cell activation requires the participation of antigen-presenting cells (APC). Once superantigen has bound class II MHC molecules on the surface of APC, it then can interact with the T cell receptor to induce T cell activation. Superantigen-mediated T lymphocyte activation, along with its consequent cytokine production is thought to be the basis for the pathophysiology of conditions such as toxic shock syndrome, Kawasaki''s disease and possibly rheumatoid arthritis. We examined the role of CD56⁺ NK lymphocytes in the interaction between superantigens and T lymphocytes. First, we found that a subpopulation of CD56⁺ cells freshly isolated from human peripheral blood expressed class II MHC molecules. The amount of HLA-DR expression varied between individuals, ranging from 9.3% to 37.7%. CD56⁺ (NK) cells were purified from the peripheral blood by cell sorting and were tested for their ability to support SEB-mediated T cell activation as assessed by surface expression of IL-2 receptor α-chain (CD25) on CD3⁺ lymphocytes. We observed that when enriched T cells were incubated with SEB in the presence of NK cells, there was a significant up-regulation of CD25 expression on the T cells. When HLA-DR⁺ cells were removed from sorted CD56⁺ populations, the remaining HLA-DR⁻ NK cells were unable to support SEB-mediated T cell activation. Also, SEB up-regulated the expression of HLA-DR on CD56⁺ cells in peripheral blood mononuclear cell (PBMC) populations after 24 h of incubation, implying that the ability of NK cells to function as superantigen-presenting cells is up-regulated by superantigens themselves. Together, these data demonstrate for the first time that human CD56⁺HLA-DR⁺ NK cells can function as superantigen-presenting cells, and imply that NK cells may be involved in the activation of non-specific T cell reactivity during early host defences against superantigen-elaborating microorganisms in vivo. Furthermore, the physical linkage of NK cells and T cells by the interaction of superantigen with HLA class II molecules and T cell receptors, respectively, may lead to NK cell activation and augmented lytic potential, helping to clear the body of superantigen-elaborating microorganisms.     

Effects of Talaromyces marneffei infection on mortality of HIV/AIDS patients in southern China: a retrospective cohort study

Objective

Talaromyces marneffei is an opportunistic infection with high morbidity among human immunodeficiency virus (HIV)/AIDS patients in Southeast Asia and southern China. Its effects on mortality in HIV/AIDS patients has not been clearly elucidated.

Immune Markers Predictive of Neuropsychiatric Symptoms in HIV-Infected Youth

The purpose of this study was to evaluate possible associations between systemic immune dysregulation (activated CD8⁺ T lymphocytes and natural killer [NK] cell count/function) and symptoms of depression and anxiety in youth with horizontally (behaviorally) acquired HIV infection. This secondary analysis of a previously collected prospective cohort included 323 youth with horizontally acquired HIV infection enrolled in the Reaching for Excellence in Adolescent Care and Health (REACH) cohort of the NICHD/NIH. A multivariable linear regression model with generalized estimating equations for intraindividual repeated measures was used to examine the relationship between flow cytometry measurements of activated T lymphocytes (CD8⁺ CD38⁺), NK cells (CD3⁻ CD16⁺ CD56⁺), and NK cell functional activity (lytic units per NK cell and per peripheral blood mononuclear cell) and their association with subsequent symptoms of depression (Center for Epidemiologic Studies depression scale) and anxiety (Revised Children''s Manifest Anxiety Scale). Higher measures of NK cell functional activity were associated with fewer anxiety symptoms measured 12 months later in crude and adjusted analyses. Higher counts of activated T cells were associated with fewer depression symptoms measured 12 months later in adjusted analysis. NK cell function and activated T-lymphocyte count may be related to subsequent symptoms of depression and anxiety.     

Tim-3 Induces Th2-Biased Immunity and Alternative Macrophage Activation during Schistosoma japonicum Infection

T cell immunoglobulin- and mucin-domain-containing molecule 3 (Tim-3) has been regarded as an important regulatory factor in both adaptive and innate immunity. Recently, Tim-3 was reported to be involved in Th2-biased immune responses in mice infected with Schistosoma japonicum, but the exact mechanism behind the involvement of Tim-3 remains unknown. The present study aims to understand the role of Tim-3 in the immune response against S. japonicum infection. Tim-3 expression was determined by flow cytometry, and increased Tim-3 expression was observed on CD4⁺ and CD8⁺ T cells, NK1.1⁺ cells, and CD11b⁺ cells from the livers of S. japonicum-infected mice. However, the increased level of Tim-3 was lower in the spleen than in the liver, and no increase in Tim-3 expression was observed on splenic CD8⁺ T cells or CD11b⁺ cells. The schistosome-induced upregulation of Tim-3 on natural killer (NK) cells was accompanied by reduced NK cell numbers in vitro and in vivo. Tim-3 antibody blockade led to upregulation of inducible nitric oxide synthase and interleukin-12 (IL-12) mRNA in CD11b⁺ cells cocultured with soluble egg antigen and downregulation of Arg1 and IL-10, which are markers of M2 macrophages. In summary, we observed schistosome-induced expression of Tim-3 on critical immune cell populations, which may be involved in the Th2-biased immune response and alternative activation of macrophages during infection.     

Immunological role of CD4<Superscript>+</Superscript>CD28<Superscript>null</Superscript> T lymphocytes,natural killer cells,and interferon-gamma in pediatric patients with sickle cell disease: relation to disease severity and response to therapy

Sickle cell disease (SCD) is associated with alterations in immune phenotypes. CD4⁺CD28^null T lymphocytes have pro-inflammatory functions and are linked to vascular diseases. To assess the percentage of CD4⁺CD28^null T lymphocytes, natural killer cells (NK), and IFN-gamma levels, we compared 40 children and adolescents with SCD with 40 healthy controls and evaluated their relation to disease severity and response to therapy. Patients with SCD steady state were studied, focusing on history of frequent vaso-occlusive crisis, hydroxyurea therapy, and IFN-gamma levels. Analysis of CD4⁺CD28^null T lymphocytes and NK cells was done by flow cytometry. Liver and cardiac iron overload were assessed. CD4⁺CD28^null T lymphocytes, NK cells, and IFN-gamma levels were significantly higher in patients than controls. Patients with history of frequent vaso-occlusive crisis and those with vascular complications had higher percentage of CD4⁺CD28^null T lymphocytes and IFN-gamma while levels were significantly lower among hydroxyurea-treated patients. CD4⁺CD28^null T lymphocytes were positively correlated to transfusional iron input while these cells and IFN-gamma were negatively correlated to cardiac T2* and duration of hydroxyurea therapy. NK cells were correlated to HbS and indirect bilirubin. Increased expression of CD4⁺CD28^null T lymphocytes highlights their role in immune dysfunction and pathophysiology of SCD complications.     

Characterisation of simian immunodeficiency virus-infected cells in pigtail macaques

Defining which cells become infected with simian immunodeficiency virus (SIV) in vivo should assist in unravelling the pathogenesis of human immunodeficiency virus (HIV)/SIV infection. HIV/SIV infection of CD4⁺ T cells resulted in down-regulation of CD3 and CD4 surface molecules in vitro, however this phenomenon is poorly characterised in vivo. Intracellular SIV p27 was studied by flow cytometry in serial blood samples and lymph node samples during acute infection of 17 SIVmac-infected pigtail macaques. Two weeks after infection, a mean of 56±6.8% the p27⁺ cells were lymphocytes negative for surface CD4 and CD3, and indeed the highest proportion of SIV infected cells were found in the small subset of CD3^LoCD4⁻CD8⁻ lymphocytes, indicating that infection has lead to down-regulation of these markers in vivo. Furthermore, the relative amount of SIV p27 within lymphocytes (based of mean fluorescence intensity) was higher in CD3^LoCD4⁻ and CD3⁻ infected cells than in CD3⁺ or CD4⁺ p27⁺ populations, consistent with greater viral production in CD4⁺ T cells down-regulating CD3 and CD4 molecules. The CD3⁻CD4⁻ infected cells expressed T cell markers CD2 and CD5 and were negative for monocyte, NK and B cell markers. The majority of infected cells were CD28⁺CD95⁺ central memory T cells. Surprisingly, p27⁺ blood lymphocytes were mostly negative for activation markers CD25 and CD69, but most of the infected lymph nodes cells were activated. Our results characterise productively-infected macaque lymphocytes in vivo. The high proportion of SIV-infected lymphocytes that are CD3⁻CD4⁻ has important implications for the in vivo study of pathogenesis of SIV/HIV infections.     

B Cell Production of Tumor Necrosis Factor in Response to Pneumocystis murina Infection in Mice

Pneumocystis species are opportunistic fungal pathogens that induce tumor necrosis factor (TNF) production by alveolar macrophages. Here we report that B cells from the draining lymph nodes as well as lung CD4⁺ T cells are important producers of TNF upon Pneumocystis murina infection. To determine the importance of B cell-derived TNF in the primary response to P. murina, we generated bone marrow chimeras whose B cells were unable to produce TNF. The lung P. murina burden at 10 days postinfection in TNF knockout (TNFKO) chimeras was significantly higher than that in wild-type (WT) chimeras, which corresponded to reduced numbers of activated CD4⁺ T cells in the lungs at this early time point. Furthermore, CD4⁺ T cells isolated from P. murina-infected TNFKO chimeras were unable to stimulate clearance of P. murina upon adoptive transfer to recombinase-deficient (RAG1KO) hosts. Together, these data indicate that B cell-derived TNF plays an important function in promoting CD4⁺ T cell expansion and production of TNF and facilitating protection against P. murina infection.     

Numerical and Functional Characteristics of Lymphocyte Subsets in Centenarians

The immune system in the aged is a very interesting subject for study. In this study, analysis was extended to extrathymic T cells as well as NK cells and conventional T cells (i.e., thymus-derived T cells) in terms of their constitution and function in both healthy and unhealthy centenarians. Middle-aged persons were used as controls. Healthy and unhealthy centenarians showed lower levels in the proportion and absolute number of lymphocytes. The major change in the constitution of lymphocyte subsets was increased levels in the proportion of NK cells (CD56⁺/CD57⁺) and extrathymic T cells (CD3⁺CD57⁺). Inversely, conventional T cells decreased in proportion and function (i.e., proliferative response to mitogen). Although NK cells increased in centenarians, NK activity by whole lymphocytes and the purified NK fraction decreased. The difference between healthy and unhealthy centenarians was small in all parameters, the only difference being a lower level of expression of CD56 antigens on CD57⁺ T cells in unhealthy centenarians. These results indicate that there is a major shift in lymphcyte population from conventional T cells to NK cells and extrathymic T cells with aging. Concerning the age-associated increases in CD56⁺ T and CD57⁺ T cells, these cells correspond to NK1⁺ T cells in mice.     

Accelerated induction of mycobacterial antigen-specific CD8+ T cells in the Mycobacterium tuberculosis-infected lung by subcutaneous vaccination with Mycobacterium bovis bacille Calmette–Guérin

Both CD4⁺ and CD8⁺ T cells are important in protection against Mycobacterium tuberculosis infection. To evaluate the effect of vaccination with Mycobacterium bovis bacille Calmette–Guérin (BCG) on the CD8⁺ T-cell response to pulmonary M. tuberculosis infection, we analyzed the kinetics of CD8⁺ T cells specific to the mycobacterial Mtb32a_309–318 epitope, which is shared by M. tuberculosis and M. bovis BCG, in the lung of mice infected with M. tuberculosis. The CD8⁺ T cells were detected by staining lymphocytes with pentameric major histocompatibility complex (MHC) class I H-2D^b–Mtb32a_209–318 peptide complex and were analysed by flow cytometry. Mtb32a-specific CD8⁺ T cells became detectable on day 14, and reached a plateau on day 21, in the lung of M. tuberculosis-infected unvaccinated mice. Subcutaneous vaccination with M. bovis BCG in the footpads induced Mtb32a-specific CD8⁺ T cells in the draining lymph nodes (LNs) on day 7 and their numbers further increased on day 14. When M. bovis BCG-vaccinated mice were exposed to pulmonaryinfection with M. tuberculosis 4 weeks after vaccination, the Mtb32a-specific CD8⁺ T cells in the infected lung became detectable on day 7 and reached a plateau on day 14, which was 1 week earlier than in the unvaccinated mice. The pulmonary CD8⁺ T cells from the BCG-vaccinated M. tuberculosis-infected mice produced interferon-γ in response to Mtb32a_209–318 peptide on day 7 of the infection, whereas those of unvaccinated mice did not. The results demonstrate that induction of mycobacterial antigen-specific protective CD8⁺ T cells in the M. tuberculosis-infected lung is accelerated by subcutaneous vaccination with M. bovis BCG.     

Antibody-dependent cellular cytotoxicity (ADCC)-mediated destruction of human immunodeficiency virus (HIV)-coated CD4+ T lymphocytes by acquired immunodeficiency syndrome (AIDS) effector cells

The acquired immunodeficiency syndrome (AIDS) is defined in clinical terms by the development of Kaposi's sarcoma and/or severe opportunistic infections in persons without predisposing conditions. A hallmark of the syndrome has been a decrease in the number of CD4⁺ T helper cells. The reduction in the frequency of the CD4⁺ lymphocytes has been postulated to be primarily the result of human immunodeficiency virus (HIV) tropism and cytophathogenicity for the T-cell subset. Yet only a small percentage of cells is actually infected with HIV. Recently, we provided evidence indicating that AIDS patients' natural killer cells can mediate normal levels of antibody-dependent cellular cytotoxicity (ADCC) despite exhibiting a defect in natural killer (NK) effector function (J Immunol 139:55, 1987). This finding prompted us to investigate whether AIDS patients' effector cells could mediate ADCC against circulating CD4⁺ T cells infected with or expressing HIV antigen. The findings reported herein demonstrate that AIDS effector cells can mediate lysis of CEM (CD4⁺ T-cell line) coated with HIV protein in the presence of HIV-specific antibody. Lysis was specific, as non-HIV-coated CEM or the addition of HIV-negative serum resulted in no lysis. We then examined HIV-coated peripheral blood-derived CD4⁺ T lymphocytes as targets in ADCC. We demonstrate that in the presence of HIV-specific antibody, HIV-coated CD4⁺ T lymphocytes serve as targets for ADCC by AIDS effector cells. The lytic activity obtained with AIDS effector cells was comparable to that obtained with normal effector cells. These results demonstrate that AIDS effector cells can mediate ADCC against HIV-coated CD4⁺ T lymphocytes and suggest that ADCC may play a rolein vivo in the pathogenesis of AIDS.     

T cell reactions of Eimeria bovis primary- and challenge-infected calves

Eimeria bovis infections commonly have clinical impact only on young animals, as homologous reinfections generally are under immunological control. So far, the nature of the immune responses delivering protection to calves has not been investigated. In this study we therefore analysed local and peripheral proliferative T cell activities of primary- and challenge-infected calves and investigated the occurrence of T cell phenotypes in the peripheral blood and in mucosal gut segments isolated either by bioptic means or by necropsies. We show that lymphocytes of E. bovis-infected calves exhibit effective, transient antigen-specific proliferative responses in the course of prepatency of primary infection but fail to react after homologous reinfection suggesting early abrogation of parasite development. Whilst in primary infection an expansion of peripheral CD4⁺ T cells was observed, reinfection had no effect on the proportions of CD4⁺, CD8⁺ subsets or γδTCR⁺ T cells. In contrast, both E. bovis primary and challenge infections had an impact on local tissue T cell distribution. Primary infection was characterised by a CD4⁺ T cell infiltration early in prepatency in ileum and later in colon mucosa, whereas CD8⁺ T cells were only found accumulating in the latter gut segment. Challenge infection led to infiltration of both CD4⁺ and CD8⁺ T cells in small intestine and large intestine segments indicating protective functions of both cell types. In contrast, infiltration of ileum and colon mucosa with γδTCR⁺ T cells was restricted to primary infection.     

Specific prebiotics modulate gut microbiota and immune activation in HAART-naive HIV-infected adults: results of the "COPA" pilot randomized trial

Intestinal mucosal immune system is an early target for human immunodeficiency virus type 1 (HIV-1) infection, resulting in CD4⁺ T-cell depletion, deterioration of gut lining, and fecal microbiota composition. We evaluated the effects of a prebiotic oligosaccharide mixture in highly active antiretroviral therapy (HAART)-naive HIV-1-infected adults. In a pilot double-blind, randomized, placebo-controlled study, 57 HAART-naive HIV-1-infected patients received a unique oligosaccharide mixture (15 or 30 g short chain galactooligosaccharides/long chain fructooligosaccharides/pectin hydrolysate-derived acidic oligosaccharides (scGOS/lcFOS/pAOS) daily) or a placebo for 12 weeks. Microbiota composition improved significantly with increased bifidobacteria, decreased Clostridium coccoides/Eubacterium rectale cluster, and decreased pathogenic Clostridium lituseburense/Clostridium histolyticum group levels upon prebiotic supplementation. In addition, a reduction of soluble CD14 (sCD14), activated CD4⁺/CD25⁺ T cells, and significantly increased natural killer (NK) cell activity when compared with control group were seen in the treatment group. The results of this pilot trial highly significantly show that dietary supplementation with a prebiotic oligosaccharide mixture results in improvement of the gut microbiota composition, reduction of sCD14, CD4⁺ T-cell activation (CD25), and improved NK cell activity in HAART-naive HIV-infected individuals.     

Moesin: A novel receptor on NK lymphocytes binds to TOMM40 on K562 leukemia cells initiating cytolysis

Natural killer lymphocytes (NK cells) are the first line of defense (innate immunity) against viral infections and leukemia since they do not require activation to deliver a lethal hit to infected/aberrant cells. In contrast, T lymphocytes require stimulation by a foreign/neo – antigen, which may take days before they are active against the pathogen (adaptive immunity). A number of receptors on activated NK cells that kill the prototypical leukemia target cell line, K562, have been identified. To date, the receptor(s) by which freshly isolated unstimulated NK cells (naïve, nNK) kill K562 has not been fully elucidated. We provide peptide sequence and immune-blot data from ligand pull down experiments that moesin, a protein that typically links the inner leaf of the plasma membrane to the cytoskeleton, additionally, in NK cells, localizes to the cell surface where it may bind to its ligand, TOMM40 (aka Haymaker, HYMKR), on leukemia cells thereby initiating their destruction. Flow cytometry experiments with a mouse monoclonal antibody (Mab) to a moesin peptide (554 to 565) were performed. Moesin was detected on the surface of CD3^–, CD16⁺ nNK cells but was not detected on the surface of freshly isolated unstimulated CD3⁺, CD16^– T cells or CD19⁺, CD16^– B cells from healthy subjects. Moesin, is therefore another marker that distinguishes unstimulated CD3^–, CD16⁺ NK cells from other non-activated lymphocytes. The anti –moesin peptide Mab was highly effective (>95% inhibition) in blocking target cell cytolysis by CD16⁺ lymphocytes demonstrating that moesin–HYMKR interaction appears to be necessary for most of the observed cell death of K562 caused by unstimulated NK cells.     

Infection of Mice with Mycobacterium avium Primes CD8 Lymphocytes for Apoptosis upon Exposure to Macrophages

Mycobacterial infection is associated with granuloma formation in which the presence of apoptosis has been recognized. The role of CD4⁺ T and CD8⁺ T cells in host protection against mycobacterial infections has been demonstrated. Previous studies, however, have shown that CD8⁺ T cells have a limited role in host defense against Mycobacterium avium infection, and we hypothesize that M. avium infection could lead to T cell apoptosis. To investigate this hypothesis, C57BL/6 mice were infected with M. avium strain 101, and the rate of apoptosis of splenic lymphocytes cultured ex vivo with peritoneal macrophages was determined and compared with that of controls. When exposed to infected macrophages ex vivo, splenic lymphocytes from M. avium-infected mice underwent apoptosis, as determined by the TUNEL assay. This increased T cell apoptosis above the control level was observed after 3 weeks but not after only 1 week of infection in mice. No splenic T cell apoptosis was observed when lymphocytes from Mycobacterium smegmatis-infected mice were cultured in the presence of M. smegmatis-infected peritoneal macrophages. Likewise, macrophages infected in vitro with heat-killed M. avium did not trigger T cell apoptosis. Culture of macrophages in different chamber from lymphocytes, separated by a transwell membrane, was not associated with increase of apoptosis compared with uninfected control, suggesting a requirement for direct cell–cell interactions to trigger lymphocyte apoptosis. Using a double staining TUNEL followed by anti-mouse CD4 or anti-mouse CD8 monoclonal antibodies, it was observed that only CD8⁺ T cells but not CD4⁺ T cells underwent apoptosis at 3 weeks of infection. In conclusion, M. avium infection in C57/BL6 mice for 3 weeks renders CD8⁺ T cells prone to apoptosis when exposed ex vivo to macrophages infected with M. avium.     

Treatment with Interleukin-7 Restores Host Defense against Pneumocystis in CD4+ T-Lymphocyte-Depleted Mice

Pneumocystis pneumonia (PCP) is a major cause of morbidity and mortality in patients with HIV infection. CD4⁺ T lymphocytes are critical for host defense against this infection, but in the absence of CD4⁺ T lymphocytes, CD8⁺ T lymphocytes may provide limited host defense. The cytokine interleukin-7 (IL-7) functions to enhance lymphocyte proliferation, survival, and recruitment of immune cells to sites of infection. However, there is little known about the role of IL-7 in PCP or its potential use as an immunotherapeutic agent. We hypothesized that treatment with recombinant human IL-7 (rhIL-7) would augment host defense against Pneumocystis and accelerate pathogen clearance in CD4-depleted mice. Control and CD4-depleted mice were infected with Pneumocystis, and rhIL-7 was administered via intraperitoneal injection. Our studies indicate that endogenous murine IL-7 is part of the normal host response to Pneumocystis murina and that administration of rhIL-7 markedly enhanced clearance of Pneumocystis in CD4-depleted mice. Additionally, we observed increased recruitment of CD8⁺ T lymphocytes to the lungs and decreased apoptosis of pulmonary CD8⁺ T lymphocytes in rhIL-7-treated animals compared to those in untreated mice. The antiapoptotic effect of rhIL-7 was associated with increased levels of Bcl-2 protein in T lymphocytes. rhIL-7 immunotherapy in CD4-depleted mice also increased the number of gamma interferon (IFN-γ)-positive CD8⁺ central memory T lymphocytes in the lungs. We conclude that rhIL-7 has a potent therapeutic effect in the treatment of murine Pneumocystis pneumonia in CD4-depleted mice. This therapeutic effect is mediated through enhanced recruitment of CD8⁺ T cells and decreased apoptosis of lung T lymphocytes, with a preferential action on central memory CD8⁺ T lymphocytes.     

Double-negative T resident memory cells of the lung react to influenza virus infection via CD11chi dendritic cells

Immunity to Influenza A virus (IAV) is controlled by conventional TCRαβ⁺ CD4⁺ and CD8⁺ T lymphocytes, which mediate protection or cause immunopathology. Here, we addressed the kinetics, differentiation, and antigen specificity of CD4⁻CD8⁻ double-negative (DN) T cells. DNT cells expressed intermediate levels of TCR/CD3 and could be further divided in γδ T cells, CD1d-reactive type I NKT cells, NK1.1⁺ NKT-like cells, and NK1.1⁻ DNT cells. NK1.1⁻ DNT cells had a separate antigen-specific repertoire in the steady-state lung, and expanded rapidly in response to IAV infection, irrespectively of the severity of infection. Up to 10% of DNT cells reacted to viral nucleoprotein. Reinfection experiments with heterosubtypic IAV revealed that viral replication was a major trigger for recruitment. Unlike conventional T cells, the NK1.1⁻ DNT cells were in a preactivated state, expressing memory markers CD44, CD11a, CD103, and the cytotoxic effector molecule FasL. DNT cells resided in the lung parenchyma, protected from intravascular labeling with CD45 antibody. The recruitment and maintenance of CCR2⁺ CCR5⁺ CXCR3⁺ NK1.1⁻ DNT cells depended on CD11c^hi dendritic cells (DCs). Functionally, DNT cells controlled the lung DC subset balance, suggesting they might act as immunoregulatory cells. In conclusion, we identify activation of resident memory NK1.1⁻ DNT cells as an integral component of the mucosal immune response to IAV infection.     

Early Changes in Frequency of Peripheral Blood Lymphocyte Subpopulations in Severe Traumatic Brain‐Injured Patients

Infections are leading causes of increased morbidity and mortality of severe traumatic brain‐injured (STBI) patients. The mechanism underlying the susceptibility to the infections is still unexplained. The purpose of the study was to investigate changes in frequency of leucocytes subpopulations in peripheral blood of patients with STBI during the course of intensive care treatment. Twenty patients with STBI were included in the study. Healthy age‐ and sex‐ volunteers served as control. Peripheral blood samples were taken from these patients at day 1, 4 and 7, and peripheral blood mononuclear cells (PBMC) were isolated. The percentage of T, B lymphocyte, NK and NKT cells as well as monocytes was analysed by simultaneous detection of surface antigens using fluorochrome‐conjugated monoclonal antibodies. The two major subsets of T lymphocytes (CD3⁺CD56^?CD4⁺ and CD3⁺CD56^?CD8⁺) and NK cells (CD3^?CD56^+dim and CD3^?CD56^+bright) were also analysed by flow cytometry. Extracranial infections were presented in 55% patients with STBI. At day 4, the percentage of T lymphocytes with cytotoxic phenotype significantly diminished and their numbers restored at day 7. The frequency of NKT cells showed the identical time‐dependent pattern, whereas the percentage of NK cells diminished on day 4 but did not restore after 7 days. The frequency of B lymphocytes did not change significantly during the time investigated, whereas the percentage of monocytes increased immediately after the injury and gradually diminished. The decrease in cells with cytotoxic phenotype might explain high incidence of susceptibility to infection of patients with STBI.     

HTLV-1-infected thymic epithelial cells convey the virus to CD4+ T lymphocytes

The human T-lymphotropic virus type-1 (HTLV-1) is the causative agent of adult T cell leukemia/lymphoma (ATL) and HTLV-1 associated myelopathy/tropical spastic paraparesis (HAM/TSP). CD4⁺T cells are the main target of HTLV-1, but other cell types are known to be infected, including immature lymphocytes. Developing T cells undergo differentiation in the thymus, through migration and interaction with the thymic microenvironment, in particular with thymic epithelial cells (TEC) the major component of this three dimensional meshwork of non-lymphoid cells. Herein, we show that TEC express the receptors for HTLV-1 and can be infected by this virus through cell–cell contact and by cell-free virus suspensions. The expression of anti-apoptosis, chemokine and adhesion molecules genes are altered in HTLV-1-infected TEC, although gene expression of antigen presentation molecules remained unchanged. Furthermore, HTLV-1-infected TEC transmitted the virus to a CD4⁺ T cell line and to CD4⁺ T cells from healthy donors, during in vitro cellular co-cultures. Altogether, our data point to the possibility that the human thymic epithelial cells play a role in the establishment and progression of HTLV-1 infection, functioning as a reservoir and transmitting the virus to maturing CD4⁺ T lymphocytes, which in turn will cause disease in the periphery.