Knocking 'em Dead: Pore-Forming Proteins in Immune Defense.

Immune cells use a variety of membrane-disrupting proteins [complement, perforin, perforin-2, granulysin, gasdermins, mixed lineage kinase domain-like pseudokinase (MLKL)] to induce different kinds of death of microbes and host cells, some of which cause inflammation. After activation by proteolytic cleavage or phosphorylation, these proteins oligomerize, bind to membrane lipids, and disrupt membrane integrity. These membrane disruptors play a critical role in both innate and adaptive immunity. Here we review our current knowledge of the functions, specificity, activation, and regulation of membrane-disrupting immune proteins and what is known about the mechanisms behind membrane damage, the structure of the pores they form, how the cells expressing these lethal proteins are protected, and how cells targeted for destruction can sometimes escape death by repairing membrane damage.

Decidual NK Cells Transfer Granulysin to Selectively Kill Bacteria in Trophoblasts.

Maternal decidual NK (dNK) cells promote placentation, but how they protect against placental infection while maintaining fetal tolerance is unclear. Here we show that human dNK cells highly express the antimicrobial peptide granulysin (GNLY) and selectively transfer it via nanotubes to extravillous trophoblasts to kill intracellular Listeria monocytogenes (Lm) without killing the trophoblast. Transfer of GNLY, but not other cell death-inducing cytotoxic granule proteins, strongly inhibits Lm in human placental cultures and in mouse and human trophoblast cell lines. Placental and fetal Lm loads are lower and pregnancy success is greatly improved in pregnant Lm-infected GNLY-transgenic mice than in wild-type mice that lack GNLY. This immune defense is not restricted to pregnancy; peripheral NK (pNK) cells also transfer GNLY to kill bacteria in macrophages and dendritic cells without killing the host cell. Nanotube transfer of GNLY allows dNK to protect against infection while leaving the maternal-fetal barrier intact.

Therapeutic effect of small extracellular vesicles from cytokine-induced memory-like natural killer cells on solid tumors.

Small extracellular vesicles (sEV) derived from diverse natural killer (NK) cell lines have proven their exceptional antitumor activities. However, sEV from human primary NK cells, especially memory-like NK cells, are rarely utilized for cancer treatment. In this study, we obtained sEV from IL-12, IL-15 and IL-18 cultured human memory-like NK cells (mNK-sEV) that showed strong cytokine-secretory ability. It was uncovered that mNK-sEV entered cancer cells via macropinocytosis and induced cell apoptosis via caspase-dependent pathway. Compared to sEV from conventionally cultured NK cells (conNK-sEV), mNK-sEV inhibited tumor growth to a greater extent. Concomitantly, pharmacokinetics and biodistribution results validated a higher accumulation of mNK-sEV than conNK-sEV in tumors of xenografted murine models. Notably, elevated containment of granulysin (GNLY) within mNK-sEV, at least in part, may contribute to the enhanced therapeutic effect. Herein our results present that mNK-sEV can be a novel class of therapeutic reagent for effective cancer treatment.

Granulysin-mediated reduction of PDZRN3 induces Cx43 gap junctions activity exacerbating skin damage in trichloroethylene hypersensitivity syndrome.

Trichloroethylene (TCE)-induced hypersensitivity syndrome (THS) has been a concern for many researchers in the field of environmental and occupational health. Currently, there is no specific treatment for THS, leaving patients to contend with severe infections arising from extensive skin lesions, consequently leading to serious adverse effects. However, the pathogenesis of severe skin damage in THS remains unclear. This study aims to investigate the specific danger signals and mechanisms underlying skin damage in THS through in vivo and in vitro experiments. We identified that cell supernatant containing 15 kDa granulysin (GNLY), released from activated CD3-CD56+NK cells or CD3+CD56+NKT cells in PBMC induced by TCE or its metabolite, promoted apoptosis in HaCaT cells. The apoptosis level decreased upon neutralization of GNLY in the supernatant by a GNLY-neutralizing antibody in HaCaT cells. Subcutaneous injection of recombinant 15 kDa GNLY exacerbated skin damage in the THS mouse model and better mimicked patients' disease states. Recombinant 15 kDa GNLY could directly induce cellular communication disorders, inflammation, and apoptosis in HaCaT cells. In addition to its cytotoxic effects, GNLY released from TCE-activated NK cells and NKT cells or synthesized GNLY alone could induce aberrant expression of the E3 ubiquitin ligase PDZRN3, causing dysregulation of the ubiquitination of the cell itself. Consequently, this resulted in the persistent opening of gap junctions composed of connexin43, thereby intensifying cellular inflammation and apoptosis through the "bystander effect". This study provides experimental evidence elucidating the mechanisms of THS skin damage and offers a novel theoretical foundation for the development of effective therapies targeting severe dermatitis induced by chemicals or drugs.

Involvement of M1-Activated Macrophages and Perforin/Granulysin Expressing Lymphocytes in IgA Vasculitis Nephritis.

We investigated the polarisation of CD68+ macrophages and perforin and granulysin distributions in kidney lymphocyte subsets of children with IgA vasculitis nephritis (IgAVN). Pro-inflammatory macrophage (M)1 (CD68/iNOS) or regulatory M2 (CD68/arginase-1) polarisation; spatial arrangement of macrophages and lymphocytes; and perforin and granulysin distribution in CD3+ and CD56+ cells were visulaised using double-labelled immunofluorescence. In contrast to the tubules, iNOS+ cells were more abundant than the arginase-1+ cells in the glomeruli. CD68+ macrophage numbers fluctuated in the glomeruli and were mostly labelled with iNOS. CD68+/arginase-1+ cells are abundant in the tubules. CD56+ cells, enclosed by CD68+ cells, were more abundant in the glomeruli than in the tubuli, and co-expressed NKp44. The glomerular and interstitial/intratubular CD56+ cells express perforin and granulysin, respectively. The CD3+ cells did not express perforin, while a minority expressed granulysin. Innate immunity, represented by M1 macrophages and CD56+ cells rich in perforin and granulysin, plays a pivotal role in the acute phase of IgAVN.

Clinical characteristics and immune profiles of patients with immune-mediated alopecia associated with COVID-19 vaccinations.

BACKGROUND: The clinical characteristics and pathomechanism for immune-mediated alopecia following COVID-19 vaccinations are not clearly characterized. OBJECTIVE: We investigated the causality and immune mechanism of COVID-19 vaccines-related alopecia areata (AA). STUDY DESIGN: 27 new-onset of AA patients after COVID-19 vaccinations and 106 vaccines-tolerant individuals were enrolled from multiple medical centers for analysis. RESULTS: The antinuclear antibody, total IgE, granulysin, and PARC/CCL18 as well as peripheral eosinophil count were significantly elevated in the patients with COVID-19 vaccines-related AA compared with those in the tolerant individuals (P = 2.03 × 10-5-0.039). In vitro lymphocyte activation test revealed that granulysin, granzyme B, and IFN-γ released from the T cells of COVID-19 vaccines-related AA patients could be significantly increased by COVID-19 vaccine excipients (polyethylene glycol 2000 and polysorbate 80) or spike protein (P = 0.002-0.04). CONCLUSIONS: Spike protein and excipients of COVID-19 vaccines could trigger T cell-mediated cytotoxicity, which contributes to the pathogenesis of immune-mediated alopecia associated with COVID-19 vaccines.

The altered HLA-DQ expression in peripheral blood T cells of chronic hepatitis B patients characterizes the function of T cells.

OBJECTIVE: This study aimed to clarify the expression of HLA-DQ and granulysin in peripheral blood T-cell subsets in patients with chronic hepatitis B virus (CHB) and to evaluate their significance in assisting CHB diagnosis and immune status assessment. METHODS: Peripheral blood from 34 CHB patients, 36 inactive HBsAg carriers and 33 healthy controls were collected, and HLA-DQ and granulysin in a series of T-cell subsets were analysed by flow cytometry. The ability to secrete IL-10 and IFN-γ and the functional T-cell subsets were measured in Treg and CD4 cells expressing HLA-DQ or not. Correlation analyses were further conducted between HLA-DQ/granulysin-related subsets and clinical indicators of HBV infection, and ROC curves were built to evaluate diagnosis efficiency of HLA-DQ-related subsets. RESULTS: HLA-DQ+ percentages in circulating CD4 T cells were downregulated in CHB patients. The proportions of HLA-DQ + Tfh in CHB were upregulated while HLA-DQ+ percentages in Treg were decreased. In terms of function, the IFN-γ secretion ability of CD4 + T cells and IL-10 secretion in Tregs were stronger in HLA-DQ+ than HLA-DQ- subsets. HLA-DQ + CD4 + T cells and HLA-DQ + Treg were negatively correlated with HBV-DNA, while HLA-DQ + Tfh and Tfc cells were positively correlated with HBV-DNA and ALT. HLA-DQ + Treg/Tfh/Tfc could help to distinguish CHB from inactive HBsAg carriers. CONCLUSION: HLA-DQ on T cells can characterize the function of T-cell subsets and analysis of HLA-DQ can help to evaluate immune status and assist in diagnosis of CHB.

Conjugation of the 9-kDa Isoform of Granulysin with Liposomes Potentiates Its Cytotoxicity.

Nine kDa granulysin (GRNLY) is a human cytolytic protein secreted by cytotoxic T lymphocytes (CTL) and NK cells of the immune system whose demonstrated physiological function is the elimination of bacteria and parasites. In previous studies by our group, the anti-tumor capacity of recombinant granulysin was demonstrated, both in vitro and in vivo. In the present work, we developed lipid nanoparticles whose surfaces can bind recombinant granulysin through the formation of a complex of coordination between the histidine tail of the protein and Ni2+ provided by a chelating lipid in the liposome composition and termed them LUV-GRNLY, for granulysin-bound large unilamellar vesicles. The objective of this formulation is to increase the granulysin concentration at the site of contact with the target cell and to increase the cytotoxicity of the administered dose. The results obtained in this work indicate that recombinant granulysin binds to the surface of the liposome with high efficiency and that its cytotoxicity is significantly increased when it is in association with liposomes. In addition, it has been demonstrated that the main mechanism of death induced by both granulysin and LUV-GRNLY is apoptosis. Jurkat-shBak cells are resistant to GRNLY and also to LUV-GRNLY, showing that LUV-GRNLY uses the mitochondrial apoptotic pathway to induce cell death. On the other hand, we show that LUV-GRNLY induces the expression of the pro-apoptotic members of the Bcl-2 family Bim and especially PUMA, although it also induced the expression of anti-apoptotic Bcl-xL. In conclusion, we demonstrate that binding of GRNLY to the surfaces of liposomes clearly augments its cytotoxic potential, with cell death executed mainly by the mitochondrial apoptotic pathway.

Upregulated serum granulysin levels in women with antiphospholipid antibody-associated recurrent miscarriage are downregulated by heparin treatment.

Purpose: Granulysin is a cytotoxic protein that simultaneously activates innate and cellular immunity. The authors aimed to evaluate whether granulysin is associated with the antiphospholipid antibody syndrome and whether heparin changes the granulysin levels. Methods: A cohort study was performed with women with antiphospholipid antibody-positive recurrent pregnancy loss (RPL). The authors examined granulysin levels under RPL and evaluated the changes in serum granulysin levels before and 1 week after the commencement of heparin treatment. Results: Serum granulysin levels before heparin treatment were significantly higher in women who tested positive for one or more types of antiphospholipid antibodies (2.75 ± 1.03 vs. 2.44 ± 0.69, p = 0.0341 by Welch's t test), particularly anti-phosphatidylethanolamine antibodies (IgG: 2.98 ± 1.09 vs. 2.51 ± 0.86, p = 0.0013; IgM: 2.85 ± 1.09 vs. 2.47 ± 0.77, p = 0.0024 by Welch's t test). After heparin treatment for 1 week, serum granulysin levels were significantly reduced (p = 0.0017 by the paired t test). The miscarriage rate was significantly higher in women whose serum granulysin levels were not reduced by heparin treatment (p = 0.0086 by Fisher's exact probability test). Conclusion: The results suggest that heparin may reduce the incidence of miscarriage by suppressing serum granulysin levels.

GRANULYSIN PEPTIDE AND GENE POLYMORPHISM IN THE PATHOGENESIS OF HASHIMOTO THYROIDITIS.

Background: Hashimoto thyroiditis (HT) is an autoimmune disease and the most common cause of hypothyroidism. The widespread lymphocyte infiltration in the thyroid gland and intolerance of the body against its thyroid antigens leads to the destruction of thyroid cells and impaired thyroid function. Granulysin (GNLY) is a cytolytic antimicrobial peptide that has been associated with a wide range of diseases such as various infections, cancer, transplantation, and skin problems. However, there are a few studies investigating the relationship between HT and granulysin. Aim: Our study aims to investigate whether granulysin levels and GNLY gene polymorphism contribute to the damaged immune response leading to HT. Material and Methods: 100 unrelated patients diagnosed with HT and 140 healthy individuals were included in our study. Frequencies of GNLY rs10180391 and rs7908 gene polymorphisms were determined using PCR- RFLP method and serum granulysin levels were determined using ELISA. Results: There is no statistical significance between patient and control groups in terms of genotype and allele frequencies of GNLY gene polymorphisms and serum levels of granulysin. Conclusion: In conclusion, granulysin and GNLY gene polymorphisms do not appear to relate to HT disease.

Gran1: A Granulysin-Derived Peptide with Potent Activity against Intracellular Mycobacterium tuberculosis.

Granulysin is an antimicrobial peptide (AMP) expressed by human T-lymphocytes and natural killer cells. Despite a remarkably broad antimicrobial spectrum, its implementation into clinical practice has been hampered by its large size and off-target effects. To circumvent these limitations, we synthesized a 29 amino acid fragment within the putative cytolytic site of Granulysin (termed "Gran1"). We evaluated the antimicrobial activity of Gran1 against the major human pathogen Mycobacterium tuberculosis (Mtb) and a panel of clinically relevant non-tuberculous mycobacteria which are notoriously difficult to treat. Gran1 efficiently inhibited the mycobacterial proliferation in the low micro molar range. Super-resolution fluorescence microscopy and scanning electron microscopy indicated that Gran1 interacts with the surface of Mtb, causing lethal distortions of the cell wall. Importantly, Gran1 showed no off-target effects (cytokine release, chemotaxis, cell death) in primary human cells or zebrafish embryos (cytotoxicity, developmental toxicity, neurotoxicity, cardiotoxicity). Gran1 was selectively internalized by macrophages, the major host cell of Mtb, and restricted the proliferation of the pathogen. Our results demonstrate that the hypothesis-driven design of AMPs is a powerful approach for the identification of small bioactive compounds with specific antimicrobial activity. Gran1 is a promising component for the design of AMP-containing nanoparticles with selective activity and favorable pharmacokinetics to be pushed forward into experimental in vivo models of infectious diseases, most notably tuberculosis.

The cytotoxic molecule granulysin is capable of inducing either chemotaxis or fugetaxis in dendritic cells depending on maturation: a role for Vδ2+ γδ T cells in the modulation of immune response to tumour?

Release of granulysin by γδ T cells contributes to tumour cell killing. A cytolytic 9000 MW isoform of granulysin kills tumour cells directly, whereas a 15 000 MW precursor has been hypothesized to cause both the maturation and migration of dendritic cell (DC) populations. Recruiting DC to a tumour is beneficial as these cells initiate adaptive immune responses, which contribute to the eradication of malignancies. In this study, Vδ2+ γδ T cells were activated by stimulation of peripheral blood mononuclear cells with zoledronic acid or Bacillus Calmette-Guérin (BCG), or were isolated and cultured with tumour targets. Although a large proportion of resting Vδ2+ γδ T cells expressed 15 000 MW granulysin, 9000 MW granulysin expression was induced only after stimulation with BCG. Increased levels of activation and granulysin secretion were also observed when Vδ2+ γδ T cells were cultured with the human B-cell lymphoma line Daudi. High concentrations of recombinant 15 000 MW granulysin caused migration and maturation of immature DC, and also initiated fugetaxis in mature DC. Conversely, low concentrations of recombinant 15 000 MW granulysin resulted in migration of mature DC, but not immature DC. Our data therefore support the hypothesis that Vδ2+ γδ T cells can release granulysin, which may modulate recruitment of DC, initiating adaptive immune responses.

Association between seminal granulysin and malondialdehyde in infertile men with varicocele and the potential effect of varicocelectomy.

This study assessed the seminal plasma granulysin and malondialdehyde (MDA) levels in patients suffering from varicocele-associated infertility prior to and after varicocelectomy. This study was conducted on 34 infertile men with varicocele (group A) and same patients after varicocelectomy (group B) and 32 fertile normozoospermic males (group C). A detailed history taking, clinical examination, scrotal doppler ultrasound for varicocele diagnosis and grading, semen analysis and estimation of seminal granulysin and MDA before and after varicocelectomy were done to all participants. The mean (SD) granulysin and MDA levels in patients with varicocele were higher than in controls with highly significant differences. Post-operatively, there was a significant reduction in mean (SD) granulysin and in MDA level. Basal seminal granulysin positively correlated with basal seminal MDA, abnormal forms and negatively correlated with basal sperm count, concentration, and progressive motility. The receiver operating characteristic curve of seminal granulysin and MDA levels were conducted for discrimination between infertility cases with varicocele and control groups. Excellent AUCs were found for both markers (AUC = 0.971, 0.991 respectively). We concluded that high levels of granulysin and MDA in the semen of infertile males with varicocele negatively impact their spermatogenesis. Varicocelectomy leads to the improvement of semen parameters and significantly decreases seminal plasma granulysin and MDA levels. Hence, seminal granulysin and MDA could be used as a prognostic test in infertile patients with varicocele.

Production of a Granulysin-Based, Tn-Targeted Cytolytic Immunotoxin Using Pulsed Electric Field Technology.

Granulysin is a protein present in the granules of human cytotoxic T lymphocytes (CTL) and natural killer (NK) cells, with cytolytic activity against microbes and tumors. Previous work demonstrated the therapeutic effect of the intratumoral injection of recombinant granulysin and of the systemic injection of an immunotoxin between granulysin and the anti-carcinoembryonic antigen single-chain Fv antibody fragment MFE23, which were produced in the yeast Pichia pastoris. In the present work, we developed a second immunotoxin combining granulysin and the anti-Tn antigen single-chain Fv antibody fragment SM3, that could have a broader application in tumor treatment than our previous immunotoxin. In addition, we optimized a method based on electroporation by pulsed electric field (PEF) to extract the remaining intracellular protein from yeast, augmenting the production and purificiation yield. The immunotoxin specifically recognized the Tn antigen on the cell surface. We also compared the thermal stability and the cytotoxic potential of the extracellular and intracellular immunotoxins on Tn-expressing human cell lines, showing that they were similar. Moreover, the bioactivity of both immunotoxins against several Tn+ cell lines was higher than that of granulysin alone.

Mechanisms of Apoptosis Resistance to NK Cell-Mediated Cytotoxicity in Cancer.

Natural killer (NK) cells are major contributors to immunosurveillance and control of tumor development by inducing apoptosis of malignant cells. Among the main mechanisms involved in NK cell-mediated cytotoxicity, the death receptor pathway and the release of granules containing perforin/granzymes stand out due to their efficacy in eliminating tumor cells. However, accumulated evidence suggest a profound immune suppression in the context of tumor progression affecting effector cells, such as NK cells, leading to decreased cytotoxicity. This diminished capability, together with the development of resistance to apoptosis by cancer cells, favor the loss of immunogenicity and promote immunosuppression, thus partially inducing NK cell-mediated killing resistance. Altered expression patterns of pro- and anti-apoptotic proteins along with genetic background comprise the main mechanisms of resistance to NK cell-related apoptosis. Herein, we summarize the main effector cytotoxic mechanisms against tumor cells, as well as the major resistance strategies acquired by tumor cells that hamper the extrinsic and intrinsic apoptotic pathways related to NK cell-mediated killing.

Systemic and Local Increase of Granulysin Expression in Cytotoxic Lymphocytes in Severe Psoriasis.

Psoriasis is considered to be a cytokine-driven immune-mediated disease, although the cell cytotoxicity mechanisms involved remain unrecognized. Herein, we analyzed granulysin expression in different lymphocyte subsets of peripheral blood of 40 psoriatic patients (20 with severe and 20 with mild psoriasis) and seven sample of psoriatic skin. The simultaneous detection of intracellular granulysin and cell surface antigens was performed using flow cytometry in peripheral blood and immunohistochemistry in skin lesions. The frequency of granulysin+ cells, mean fluorescence intensity for granulysin, and the frequency of CD8+ T lymphocytes, NK cells, and NKT cells expressing granulysin molecules in peripheral blood were significantly higher in patients with severe psoriasis compared to mild disease and healthy individuals. These were also correlated with disease severity. Furthermore, granulysin+ cells, CD8+granulysin+ T lymphocytes, and CD56+granulysin+ NK cells were present in a higher frequency in the epidermal basal cell layer and in the dermal infiltrate of lesional skin as compared to non-lesional and healthy skin. In conclusion, granulysin+ cytotoxic cells are upregulated in blood and lesions of patients with psoriasis suggesting the involvement of granulysin mediated cytotoxicity in psoriasis pathogenesis.

Granulysin as a novel factor for the prognosis of the clinical course of chickenpox.

Granulysin is a recently discovered cytolytic protein of natural killer (NK) cells and cytotoxic T lymphocytes. Studies of healthy and immunocompromised patients with primary or recurrent varicella-zoster infections demonstrate the importance of virus-specific cellular immunity in controlling viral replication, but also some studies presented granulysin as a molecule that can play a role in chickenpox immunopathogenesis. This study investigated possible correlation between serum granulysin levels and clinical course of chickenpox. A total of 69 patients with chickenpox were included in the study. We measured the levels of granulysin and percentage count for CD4+, CD8+ and NK cells in serum for all patients and healthy controls. For detection and quantification of granulysin in sera, we performed ELISA test and flow cytometry for detection, identification and percentage measurement of T and B lymphocytes. Descriptive methods, analysis of variance and multivariate logistic regression were used for statistical data analysis. We found respective correlation between serum granulysin level and severity of clinical presentation. These findings can be a good input for further studies, since there is no relevant prognostic parameter of chickenpox in everyday clinical practice. Granulysin, as a therapeutic, also deserves to be a point of interests in the future. If we prove its potential to stop dissemination of human herpes viruses, possibilities to use it in some life-threatening forms of viral disease can be very valuable.

Assessment of seminal granulysin in infertile men with varicocele.

Varicocele has a common association with male infertility, but its exact role is still debated. Apoptosis has been suggested as one of the mechanisms of varicocele-associated infertility. Granulysin is a molecule that plays a role in apoptosis with no previous study about its role in male infertility. This case-controlled study aimed to assess seminal plasma granulysin level in infertile patients with varicocele. This study involved 90 men that were allocated into fertile normozoospermic men (n = 20), infertile men without varicocele (n = 30) and infertile men with varicocele (n = 40). These men were subjected to history taking, clinical examination, semen analysis and estimation of seminal granulysin. In general, seminal granulysin level was significantly elevated in infertile men compared with fertile men. Infertile men with varicocele showed significantly higher seminal granulysin compared with infertile men without varicocele, in bilateral varicocele cases and in grade III varicocele. Seminal granulysin level was negatively correlated with sperm concentration, sperm motility, sperm normal forms percentage and testicular volumes. It is concluded that increased seminal granulysin has a negative impact on spermatogenesis in infertile men in general and in infertile men associated with varicocele in particular.

Clinicopathologic analysis of atypical hand, foot, and mouth disease in adult patients.

BACKGROUND: Hand, foot, and mouth disease is a contagious viral infection usually affecting children. A resurgence of cases in adults, mainly caused by coxsackievirus A6 and with an atypical and more severe presentation, has taken place. OBJECTIVE: The goal was to examine the clinical, histologic, and immunohistochemical features of this disease in adults. METHODS: This is a retrospective study on documented cases of adult hand, foot, and mouth disease from France's Dermatology Department of Strasbourg University Hospital and Bel-Air Hospital in Thionville. RESULTS: Six patients with severe and atypical presentation were included, 4 caused by coxsackievirus A6. The histologic features were: spongiosis, neutrophilic exocytosis, massive keratinocyte necrosis, shadow cells in the upper epidermis, vacuolization of basal cells, necrotic cells in follicles and sweat glands, dense superficial dermal infiltrate of CD3+ lymphocytes, and strong granulysin expression. LIMITATIONS: This is a retrospective case series. CONCLUSION: In adult patients presenting with atypical hand, foot, and mouth disease caused by coxsackievirus A6, biopsy specimens show distinctive changes in the epidermis but also in adnexal structures. The inflammatory infiltrate is made of T cells with a cytotoxic profile, with numerous granulysin-positive cells, as observed in severe drug-induced eruption with necrosis of keratinocytes.

Hypoxia promotes Mycobacterium tuberculosis-specific up-regulation of granulysin in human T cells.

Oxygen tension affects local immune responses in inflammation and infection. In tuberculosis mycobacteria avoid hypoxic areas and preferentially persist and reactivate in the oxygen-rich apex of the lung. Oxygen restriction activates antimicrobial effector mechanisms in macrophages and restricts growth of intracellular Mycobacterium tuberculosis (M.Tb). The effect of oxygen restriction on T cell-mediated antimicrobial effector mechanisms is unknown. Therefore we determined the influence of hypoxia on the expression of granulysin, an antimicrobial peptide of lymphocytes. Hypoxia increased the antigen-specific up-regulation of granulysin mRNA and protein in human CD4(+) and CD8(+) T lymphocytes. This observation was functionally relevant, because oxygen restriction supported the growth-limiting effect of antigen-specific T cells against virulent M.Tb residing in primary human macrophages. Our results provide evidence that oxygen restriction promotes the expression of granulysin and suggest that this effect-in conjunction with additional T cell-mediated immune responses-supports protection against mycobacteria. The therapeutic modulation of oxygen availability may offer a new strategy for the host-directed therapy of infectious diseases with intracellular pathogens.