In vitro expansion of T-cell-receptor Valpha2.3(+) CD4(+) T lymphocytes in HLA-DR17(3), DQ2(+) individuals upon stimulation with Mycobacterium tuberculosis

Limited T cell receptor repertoire diversity in tuberculosis patients correlates with clinical severity

Background

The importance of CD4⁺ and CD8⁺ T cells in protection against tuberculosis (TB) is well known, however, the association between changes to the T cell repertoire and disease presentation has never been analyzed. Characterization of T-cells in TB patients in previous study only analyzed the TCR β chain and omitted analysis of the Vα family even though α chain also contribute to antigen recognition. Furthermore, limited information is available regarding the heterogeneity compartment and overall function of the T cells in TB patients as well as the common TCR structural features of Mtb antigen specific T cells among the vast numbers of TB patients.

Methodology/Principal Findings

CDR3 spectratypes of CD4⁺ and CD8⁺ T cells were analyzed from 86 patients with TB exhibiting differing degrees of disease severity, and CDR3 spectratype complexity scoring system was used to characterize TCR repertoire diversity. TB patients with history of other chronic disease and other bacterial or viral infections were excluded for the study to decrease the likely contribution of TCRs specific to non-TB antigens as far as possible. Each patient was age-matched with a healthy donor group to control for age variability. Results showed that healthy controls had a normally diversified TCR repertoire while TB patients represented with restricted TCR repertoire. Patients with mild disease had the highest diversity of TCR repertoire while severely infected patients had the lowest, which suggest TCR repertoire diversity inversely correlates with disease severity. In addition, TB patients showed preferred usage of certain TCR types and have a bias in the usage of variable (V) and joining (J) gene segments and N nucleotide insertions.

Conclusions/Significance

Results from this study promote a better knowledge about the public characteristics of T cells among TB patients and provides new insight into the TCR repertoire associated with clinic presentation in TB patients.

CD4+ T cells in sarcoidosis: targets and tools

Activated pulmonary T-helper type 1 lymphocytes are essential for the inflammatory process in sarcoidosis. Both the T cells and their mediators promoting inflammation may constitute possible targets for immunotherapy. A particular T-cell subset, the T-cell receptor AV2S3(+) CD4(+) T cells, are found at dramatically increased levels in the bronchoalveolar lavage fluid of a subpopulation of sarcoidosis patients with active disease. This particular T-cell subset may be used as a tool to reveal a sarcoidosis-specific antigen. Recent studies of natural killer T cells and T regulatory cells from patients with sarcoidosis have described abnormalities that may be relevant for the inflammatory process in this disease. These findings are exciting news and may be of help for designing new treatment strategies.

The Werner syndrome protein functions in repair of Cr(VI)-induced replication-associated DNA damage

Werner syndrome is a premature aging disorder characterized by cancer predisposition that is caused by loss of the Werner syndrome protein (WRN) helicase/exonuclease DNA repair protein. Hexavalent chromium is an environmental carcinogen and genotoxicant that is associated with respiratory cancers and induces several forms of DNA damage, including lesions that interfere with DNA replication. Based on the evidence that WRN protein facilitates repair of stalled and collapsed replication forks, we hypothesized that WRN functions in the cellular response to and recovery from Cr(VI)-induced genotoxicity and genomic instability. Here we report that human cells deficient in WRN protein are hypersensitive to Cr(VI) toxicity, and exhibit a delayed reduction in DNA breaks and stalled replication forks, indicated by gammaH2AX foci, during recovery from Cr(VI) exposure. Cr(VI)-induced WRN protein translocation from the nucleoli into nucleoplasmic foci in S-phase cells, and these foci colocalized with gammaH2AX foci indicating WRN responds to replication-associated DNA damage. As further evidence that Cr(VI) triggers stalled DNA replication, we observed Cr(VI) treatment induced an accumulation of cells in S-phase that exhibited high levels of gammaH2AX foci. Therefore, these data demonstrate a novel role for WRN protein in cellular protection against the environmental genotoxicant Cr(VI) and further provide evidence that Cr(VI) induces DNA replicative stress which has implications for aging and cancer.

T cell responses to mycobacterial catalase-peroxidase profile a pathogenic antigen in systemic sarcoidosis

Sarcoidosis is a systemic granulomatous disease associated with local epithelioid granulomas, CD4(+) T cells, and Th1 cytokines. The tissue Ags that drive this granulomatous inflammation are uncertain. In this study, we used IFN-gamma-ELISPOT assays and flow cytometry to assess lung and blood T cell responses to the candidate pathogenic Ag, Mycobacterium tuberculosis catalase-peroxidase (mKatG) in patients with sarcoidosis from two centers. Despite differences in patient phenotypic, genetic, and prognostic characteristics, we report that T cell responses to mKatG were remarkably similar in these cohorts, with higher frequencies of mKatG-reactive, IFN-gamma-expressing T cells in the blood of sarcoidosis patients compared with nontuberculosis sensitized healthy controls, and (in a subset) in greater numbers than T cells reactive to purified protein derivative. In sarcoidosis, mKatG-reactive CD4(+) Th1 cells preferentially accumulated in the lung, indicating a compartmentalized response. Patients with or without Löfgren syndrome had similar frequencies of mKatG specific IFN-gamma-expressing blood T cells. Circulating mKatG-reactive T cells were found in chronic active sarcoidosis but not in patients with inactive disease. Together, these results demonstrate that T cell responses to mKatG in sarcoidosis fit a profile expected for a pathogenic Ag, supporting an immunotherapeutic approach to this disease.

Influence of HLA-DRB1 alleles on Th1 and Th2 cytokine response to Mycobacterium tuberculosis antigens in pulmonary tuberculosis

The influence of human leukocyte antigens (HLA) on the immune response is well established. We investigated the regulatory role of HLA-DRB1 alleles on cytokine response to live M. tuberculosis and its culture filtrate antigen (CFA) in normal healthy subjects (NHS) and pulmonary tuberculosis (PTB) patients. Th1 (IFN-gamma and IL-12p40), Th2 (IL-4 and IL-5), pro-inflammatory (IL-6 and IL-8) and anti-inflammatory (TGF-beta and IL-10) cytokines were measured by ELISA in 72-h-old peripheral blood mononuclear cell culture supernatants from 58 NHS and 48 PTB patients. HLA-DRB1 genotyping was carried out by polymerase chain reaction and dot-blot hybridization with biotinylated sequence-specific oligonucleotide probes and detection by chemiluminescence. In response to live M. tuberculosis and CFA, significantly increased levels of IL-6, IL-8 and TGF-beta and decreased IFN-gamma, IL-12p40 and IL-10 were seen in PTB patients compared to NHS. We observed a significantly increased IFN-gamma response in HLA-DRB1*03-positive NHS (p=0.03) and decreased IFN-gamma response in HLA-DRB1*15-positive patients (p=0.04) than respective allele-negative individuals. An increased level of IL-12p40 in DRB1*10 (p=0.02) and IL-10 in DRB1*12- (p=0.03) positive NHS and an increased level of IL-6 in DRB1*04- (p=0.02) positive patients were observed. The study suggests that HLA-DRB1 alleles differentially modulate the various cytokine responses to M. tuberculosis antigens, which may influence the cellular and humoral immune responses to M. tuberculosis infection in a susceptible host.

Role of CD4+ T cells in sarcoidosis

Activated pulmonary CD4(+) T lymphocytes of the Th-1 type are essential for the inflammatory process in sarcoidosis, and IFN-gamma production is crucial for the characteristic granuloma formation. Both the T cells and their inflammatory mediators may constitute possible targets for immunotherapy. A particular T-cell subset, the T-cell receptor (TCR) AV2S3(+) bronchoalveolar lavage (BAL) CD4(+) T cells, is found at dramatically increased levels in the BAL fluid of human leukocyte antigen (HLA)-DRB1*0301-positive and/or HLA-DRB3*0101-positive patients with sarcoidosis. The AV2S3(+) BAL CD4(+) T cells strongly associate with the sarcoid inflammation, and future studies on this particular T-cell subset to reveal their specificity may lead to the identification of sarcoidosis-specific antigen(s). T-cell subpopulations with regulatory functions (i.e., natural killer T cells and T regulatory cells) have recently been described as abnormal in sarcoidosis. Dysfunctional regulatory T cells may allow T effector cells to contribute to the formation of granulomas, and they may thus be relevant for the inflammatory process in this disease. These findings are exciting news and will be of help in designing new treatment strategies.

Human CD56bright and CD56dim Natural Killer Cell Subsets Respond Differentially to Direct Stimulation with Mycobacterium bovis Bacillus Calmette-Guerin

Mycobacterium bovis bacillus Calmette-Guérin (BCG) is capable of directly stimulating several effector functions of human natural killer (NK) cells in the absence of interleukin-12 and professional antigen presenting cells. To assess the contribution of two main human NK-cell subsets (CD56(dim) and CD56(bright)) to the overall in vitro NK-cell response to BCG, peripheral blood mononuclear cells depleted of nylon wool-adherent cells or purified NK cells were stimulated with live BCG. By combining intranuclear bromodeoxyuridine (BrdU) staining and analysis of CD56 marker intensity, statistically higher percentages of BrdU(+) cells were found among the CD56(bright) subset than the CD56(dim) subset after 6 days of stimulation with BCG. Similarly, evaluation of intracellular interferon-gamma (IFN-gamma) revealed that CD56(bright) cells were those mainly involved in IFN-gamma production in response to BCG. In contrast, the CD56(dim) subset contained higher levels of perforin and granzyme A, two key molecules for exocytosis-mediated cytotoxicity, than the CD56(bright) subset. Although 16-20-h stimulation with BCG did not substantially alter the expression of cytotoxic molecules by the two subsets, a decrease in perforin content was observed in the CD56(dim), but not in the CD56(bright) subset, following 4-h incubation with the NK-sensitive target K562 cell line. This decrease in perforin content correlated with the induction by BCG-stimulated NK cells, of early markers of apoptosis on target cells to a greater extent than unstimulated cells suggesting a major role for the CD56(dim) subset in cytotoxic activity in response to BCG. Taken together, these results demonstrate that CD56(bright) and CD56(dim) human NK-cell subsets exert different functional activities in response to a live bacterial pathogen.

Functional characterization of human natural killer cells responding to Mycobacterium bovis bacille Calmette-Guérin

The kinetics of activation and induction of several effector functions of human natural killer (NK) cells in response to Mycobacterium bovis bacille Calmette-Guérin (BCG) were investigated. Owing to the central role of monocytes/macrophages (MM) in the initiation and maintenance of the immune response to pathogens, two different experimental culture conditions were analysed. In the first, monocyte-depleted nylon wool non-adherent (NW) cells from healthy donors were stimulated with autologous MM preinfected with BCG (intracellular BCG). In the second, the NW cells were directly incubated with BCG, which was therefore extracellular. In the presence of MM, CD4+ T lymphocytes were the cell subset mainly expressing the activation marker, CD25, and proliferating with a peak after 7 days of culture. In contrast, in response to extracellular BCG, the peak of the proliferative response was observed after 6 days of stimulation, and CD56+ CD3- cells (NK cells) were the cell subset preferentially involved. Such proliferation of NK cells did not require a prior sensitization to mycobacterial antigens, and appeared to be dependent upon contact between cell populations and bacteria. Following stimulation with extracellular BCG, the majority of interferon-gamma (IFN-gamma)-producing cells were NK cells, with a peak IFN-gamma production at 24-30 hr. Interleukin (IL)-2 and IL-4 were not detectable in NK cells or in CD3+ T lymphocytes at any time tested. IL-12 was not detectable in the culture supernatant of NW cells stimulated with extracellular BCG. Compared to the non-stimulated NW cells, the NW cells incubated for 16-20 hr with BCG induced the highest levels of expression of apoptotic/death marker on the NK-sensitive K562 cell line. BCG also induced expression of the activation marker, CD25, and proliferation, IFN-gamma production and cytotoxic activity, on negatively selected CD56+ CD3- cells. Altogether, the results of this study demonstrate that extracellular mycobacteria activate several NK-cell functions and suggest a possible alternative mechanism of NK-cell activation as the first line of defence against mycobacterial infections.

Human leucocyte antigen-A2 restricted and Mycobacterium tuberculosis 19-kDa antigen-specific CD8+ T-cell responses are oligoclonal and exhibit a T-cell cytotoxic type 2 response cytokine-secretion pattern

CD8+ T cells can be grouped into two different types of secretory T lymphocytes, based on the cytokine-secretion pattern upon antigen exposure: those with a T-cell cytotoxic type 1 response (Tc1), which secrete interferon-gamma (IFN-gamma), or those with a T-cell cytotoxic type 2 response, which secrete interleukin (IL)-4 and IL-10. We examined the CD8+ T-cell response directed against an immunodominant human leucocyte antigen (HLA)-A2-presented peptide derived from a 19-kDa Mycobacterium tuberculosis-associated antigen. T cells were examined by functional analysis and by T-cell receptor (TCR) complementarity-determining region 3 (CDR3)-spectratyping, which defines the complexity of a T-cell response. T-cell stimulation with the immunodominant VLTDGNPPEV epitope yielded a Tc2 (IL-4) cytokine-secretion pattern and resulted in oligoclonal expansion of TCR-variable beta chain (VB) families, which differed from patient to patient. Generation of T-cell clones corroborated the notion that the CD8+ T-cell response directed against the HLA-A2-presented VLTDGNPPEV epitope leads to a Tc2 cytokine-secretion pattern in CD8+ T cells, as defined by IL-4 and granulocyte-macrophage colony-stimulating factor (GM-CSF) release. Characterization of the cytokine-secretion profile in HLA-A2/VLTDGNPPEV-tetramer sorted T cells from patients with active tuberculosis supported this observation: peptide-specific T cells from three of three patients secreted IL-4 and only one of three patients produced IFN-gamma in response to the nominal target epitope. Permutation of this T-cell epitope may aid to elicit a qualitatively different CD8+ T-cell response in patients with M. tuberculosis infection.