Lesional T cells and dermal dendrocytes in psoriasis plaque express increased levels of granulysin

Circulating T Cell Subsets in Type 1 Diabetes

Type 1 diabetes (T1D) is a complex disease driven by the immune system attacking the insulin-producing beta cells in the pancreas. Understanding the role of different T cell subpopulations in the development and progression of T1D is crucial. By employing flow cytometry to compare the characteristics of T cells, we can pinpoint potential indicators of treatment response or therapeutic inefficacy. Our study reveals elevated prolactin (PRL) levels in T1D patients, along with a decreased production of key cytokines. Additionally, PD1 appears to play a significant role in T1D. Notably, PRL levels correlate with an earlier disease onset and a specific T cell phenotype, hinting at the potential influence of PRL. These findings highlight the need for further research to identify promising cellular targets for more effective and tailored therapies.

Serum Granulysin as a Possible Key Marker of Vitiligo Activity and Severity

Background

Vitiligo is an immune-mediated, chronic skin condition that affects both the innate and adaptive immune systems. Antimicrobial peptide overexpression is one of its defining characteristics. Granulysin (GNLY), an antimicrobial peptide, may play a role in the pathogenesis of various autoimmune diseases.

Objectives

To estimate the serum GNLY levels in vitiligo patients and to correlate those levels with the severity and activity of the disease.

Materials and Methods

This case-control study included 60 non-segmental vitiligo patients (Group A) and a control group of 60 people who were matched for age and sex, appeared to be in good health, and were not suffering from vitiligo (Group B). The serum granulysin levels of all subjects were measured using an enzyme-linked immunosorbent assay.

Results

When compared to the control group, vitiligo patients had significantly higher serum GNLY levels (P = 0.001). When compared to patients with stable disease, those with active vitiligo had significantly higher serum GNLY levels (P = 0.008). Additionally, there was a positive correlation between the serum GNLY levels and the vitiligo area severity index and vitiligo disease activity scores (P = 0.004 and <0.001, respectively).

Limitations

Study population was relatively small. Evaluation of serum granulysin before and after treatment could have been more beneficial.

Conclusions

Blood granulysin levels could contribute to the pathogenesis of vitiligo. A higher serum granulysin level may also be a trustworthy predictor of the severity and progression of a disease.

Detecting Lesional Granulysin Levels for Rapid Diagnosis of Cytotoxic T lymphocyte-Mediated Bullous Skin Disorders

BACKGROUND

Bullous skin disorders are induced by different pathomechanisms and several are emergent, including Stevens-Johnson syndrome/toxic epidermal necrolysis (SJS/TEN). Rapid diagnostic methods for SJS/TEN or cytotoxic T-lymphocyte (CTL)-mediated bullous disorders are crucial for early treatment. Granulysin, primarily expressed by CTLs, is a specific cytotoxic protein responsible for SJS/TEN and similar skin reactions.

OBJECTIVE

To assess granulysin levels in blister fluids to differentiate SJS/TEN and similar CTL-mediated bullous reactions from other autoimmune bullous disorders.

METHODS

Using ELISA, we measured granulysin in blister fluids from patients with bullous skin disorders, including SJS/TEN, erythema multiforme major, bullous fixed-drug eruption, bullous lupus erythematosus, paraneoplastic pemphigus, pemphigus vulgaris, bullous pemphigoid, purpura fulminans-related bullae, and hand-foot syndrome/hand-foot-skin reactions. We compared serum and blister granulysin levels in patients with SJS/TEN presenting varying severity, monitoring serial granulysin levels from acute to late stages.

RESULTS

Overall, 144 patients presenting with bullous skin disorders were enrolled. Blister granulysin levels (mean ± SD) in CTL-mediated disorders, including TEN (n = 28; 3938.7 ± 3475.7), SJS-TEN overlapping (n = 22; 1440.4 ± 1179.6), SJS (n = 14; 542.0 ± 503.2), erythema multiforme major (n = 7; 766.3 ± 1073.7), generalized bullous fixed-drug eruption (n = 10; 720.4 ± 858.3), and localized bullous fixed-drug eruption (n = 16; 69.0 ± 56.4), were significantly higher than in non-CTL-mediated bullous disorders (P < .0001), including bullous lupus erythematosus (n = 3; 22.7 ± 20.1), paraneoplastic pemphigus (n = 3; 20.3 ± 8.6), pemphigus vulgaris (n = 3; 4.4 ± 2.8), bullous pemphigoid (n = 18; 4.0 ± 2.7), purpura fulminans (n = 4; 5.9 ± 5.5), and hand-foot syndrome/hand-foot-skin reactions (n = 6; 4.6 ± 3.5). Blister granulysin levels correlated with clinical severity of SJS/TEN (P < .0001).

CONCLUSIONS

Determination of blister granulysin levels is a noninvasive and useful tool for rapid differential diagnosis of SJS/TEN and other similar CTL-mediated bullous skin disorders for treatment selection.

The role of GNLY gene polymorphisms in psoriasis pathogenesis

BACKGROUND

Psoriasis is a systemic inflammatory disorder that involves complex pathogenic interactions between the innate and adaptive immune systems. The most accepted mechanism in the etiopathogenesis of psoriasis is the induction of inflammation with keratinocyte hyperproliferation. Granulysin (GNLY) is a cytolytic antimicrobial peptide (AMP) that is secreted together with granzyme and perforin from the granules of human cytotoxic T lymphocytes (CTLs) and natural killer (NK) cells. It has been immunohistochemically proven that the expression of granulysin is increased in lesions of psoriasis.

OBJECTIVE

This study aimed to investigate the relationship between psoriasis disease and granulysin gene polymorphisms.

METHODS

GNLY rs7908 and rs10180391 polymorphisms were studied by PCR-RFLP in 100 psoriasis patients under treatment in the Dermatology Polyclinic of Bulent Ecevit University. In addition, 100 healthy individuals with similar age and sex distribution were used as a control group.

RESULTS

In the control group, GNLY rs7908 CC genotype was significantly higher than in psoriasis patients (P= 0.031; OR= 0.305; Cl= 0.305 (0.121 - 0.773). In our study, the genotype distributions in patients and control groups were GNLY rs7908 (SNP) GG (51%, 37%), GC (41%, 44%), CC (8%, 19%); GNLY rs10180391 (SNP) from the CC (41%, 44%), CT (42%, % 41), TT (17%, 15%).

STUDY LIMITATIONS

The study only included Turkish patients.

CONCLUSION

Our findings showed that GNLY rs7908 CC genotype and C allele had a protective effect against psoriasis and decreased the disease severity (according to PASI score), whereas rs10180391 SNP did not show any effective role in psoriasis pathogenesis.

Cytotoxic T lymphocytes as a potential brake of keratinocyte proliferation in psoriasis

Psoriasis is a chronic papulosquamous skin disease, histologically characterized by epidermal hyperproliferation and dermal infiltration of inflammatory cells. The majority of T lymphocytes infiltrating dermis are CD4+ T lymphocytes secreting type 1 and type 17 cytokines. These cytokines are responsible for triggering keratinocyte proliferation as well as chemokine secretion and subsequent migration of other inflammatory cells in the skin. Contrarily, lymphocytes that accumulate in epidermis are mainly CD8+ T lymphocytes. According to the recent findings, these cells can also secrete type 1 and type 17 cytokines. However, it is demonstrated so far that epidermal CD8+ T lymphocytes contain higher amounts of cytolytic molecules, such as perforin, granzyme B and granulysin whose role in psoriasis pathogenesis is still unknown. Therefore, in this article we hypothesize the active involvement of cell mediated cytotoxicity in killing the proliferating keratinocytes as a mechanism of potential self-defense and possible brake in psoriatic plaque formation, maintaining skin homeostasis.

Granulysin expression increases with increasing clinical severity of psoriasis

BACKGROUND

Psoriasis is an erythematosquamous dermatosis, which has strong expression of antimicrobial peptides (AMPs), imparting a high resistance to lesional skin infection. Granulysin is a proinflammatory AMP that has been found in some infection-resistant dermatoses.

AIM

To assess granulysin expression in psoriasis.

METHODS

Immunohistochemical expression of granulysin was assessed in lesional skin biopsies taken from 30 patients with psoriasis and 10 normal skin specimens from healthy controls (HCs) matched for age, gender and skin site. Granulysin expression was found to be high in 11 patients (36.7%), moderate in 10 (33.3%) and low in 9 (30%). A highly significant (P = 0.001) difference in granulysin expression between patients with psoriasis and HCs was found. There were also significant differences in granulysin expression between patients with low Psoriasis Area and Severity Index (PASI) (≤ 10) and those with high PASI (> 10) (P = 0.001), and between patients with early-onset (< 40 years of age) and those with late-onset (> 40 years of age) disease (P < 0.04). There was a significant (P = 0.001) positive correlation between granulysin expression and PASI (r = 0.84) and a significant (P = 0.02) negative correlation with age of onset (r = -0.38). Patients with psoriasis hadhigh granulysin expression, which increased with increased clinical severity of the disease.

CONCLUSIONS

These findings suggest a role for granulysin in psoriasis pathogenesis, and may explain the triggering effect of skin infection in psoriasis. If the pathogenic role of granulysin is substantiated by further studies, granulysin may be a potential target for immunomodulatory therapy for psoriasis.

Cytotoxic proteins and therapeutic targets in severe cutaneous adverse reactions

Severe cutaneous adverse reactions (SCARs), such as Stevens-Johnson syndrome (SJS) and toxic epidermal necrosis (TEN), are rare but life-threatening conditions induced mainly by a variety of drugs. Until now, an effective treatment for SJS/TEN still remains unavailable. Current studies have suggested that the pathobiology of drug-mediated SJS and TEN involves major histocompatibility class (MHC) I-restricted activation of cytotoxic T lymphocytes (CTLs) response. This CTLs response requires several cytotoxic signals or mediators, including granulysin, perforin/granzyme B, and Fas/Fas ligand, to trigger extensive keratinocyte death. In this article, we will discuss the cytotoxic mechanisms of severe cutaneous adverse reactions and their potential applications on therapeutics for this disease.

Analysis of granulysin-mediated cytotoxicity in peripheral blood of patients with psoriatic arthritis

The objective of the present study was to investigate possible changes in granulysin (GNLY)-mediated cytotoxicity of peripheral blood lymphocytes in psoriatic arthritis (PsA) patients with respect to different phases of the disease. We prospectively enrolled 25 PsA patients in the active phase, 26 PsA patients in remission and 24 healthy controls. The simultaneous detection of intracellular GNLY and cell surface antigens (CD3 and CD56) was performed with flow cytometry. GNLY apoptotic protein was visualised by immunocytochemistry. Natural killer (NK) cell cytotoxicity was analysed with a cytotoxicity assay against human erythroleukaemia K-562 cells. The percentage of GNLY(+) cells did not differ significantly between PsA patients in the acute phase and those in remission; however, it was always higher than in healthy examinees due to the increased percentage of GNLY(+) cells within T cells, NKT cells, and both, and in the CD56(+dim) and CD56(+bright) NK subsets. The mean fluorescence intensity for GNLY was higher in all lymphocyte subpopulations in the acute phase than in remission and in healthy controls. Accordingly, GNLY-mediated NK cell cytotoxicity against K-562 cells of active phase PsA patients was significantly higher than that in patients in remission or in healthy controls. These findings demonstrated the involvement of GNLY in the worsening of PsA and suggested that GNLY mediated the development of joint lesions.

Scid mouse model of psoriasis: a unique tool for drug development of autoreactive T-cell and th-17 cell-mediated autoimmune diseases

In both skin and synovial tissues of psoriatic arthritis (PsA) patients, there are prominent lymphocytic infiltrates localized to the dermal papillae in the skin and the sublining layer stroma in the joint. T-cells, with a predominance of CD4+ lymphocytes, are the most significant lymphocytes in the tissues; in contrast, this ratio is reversed in the epidermis, synovial fluid compartment, and at the enthesis, where CD8+ T-cells are more common. This differential tropism of CD8+ T-cell suggests that the CD8+ T-cells may be driving the immune response in the joint and skin. This is supported by an association with MHC class I. The cytokine network in the psoriatic skin and synovium is dominated by monocyte and T-cell-derived cytokines: IL-1β, IL-2, IL-10, IFN-γ, and TNF-α. In PsA synovium, higher levels of IFN-γ, IL-2, and IL-10 have been detected than in psoriatic skin. An analysis of T-cell receptor beta-chain variable (TCRβV) gene repertoires revealed common expansions in both skin and synovial inflammatory sites, suggesting an important role for cognate T-cell responses in the pathogenesis of PsA and that the inciting antigen may be identical or homologous between the afflicted skin and synovium. Traditionally, T-cells have been classified as T helper 1 (Th1) or Th2 cells by production of defining cytokines, IFN-γ and IL-4, respectively. Recently, a new type of T-cell, Th17, has been linked to autoimmune inflammation. T-helper 17 (Th17) cells are a unique effector CD4+ T-cell subset characterized by the production of interleukin (IL)-17. Murine diseases that were previously considered to be pure Th1-mediated responses have been shown to contain mixed populations of Th1 and Th17 cells. Also, in humans, a critical immunoregulatory role of Th-17 cells in infectious and autoimmune diseases has been identified. It has been postulated that IL-17 may be important in psoriasis. Our initial observations demonstrate that IL-17 and its receptor system are important for PsA also. In in vivo and in vitro studies we have demonstrated that IL-17/IL-17R are enriched in skin, synovial tissue, and synovial fluid of psoriatic arthritis patients and Th17 cells are functionally significant in the pathogenesis of psoriasis and psoriatic arthritis. Here we will share our experience of the SCID mouse model of psoriasis in respect to its use in investigating psoriatic diseases and development of immune-based drugs for psoriasis, psoriatic arthritis, and other autoimmune diseases.

The Impact of Preeclampsia on Gene Expression at the Maternal-Fetal Interface

Preeclampsia (PE) impacts 8 million mother-infant pairs worldwide each year. This human pregnancy-specific disease characterized by hypertension and proteinuria accounts for significant maternal and neonatal morbidity and mortality. The current theory of the pathogenesis of PE as reviewed by Drs. Christopher Redman and Ian Sargent is thought to occur as a 2-stage process with poor placentation in the first half of pregnancy resulting in the maternal response in the second half of pregnancy. Our studies have focused on understanding the placental contribution to this serious disease by examining the gene expression profile of the deciduas basalis or basal plate, the region of the placenta involved in the "poor placentation". In this review we present summaries of our microarray datasets both of normal placentation and those gene expression changes resulting in the context of PE. Additionally, we have taken this opportunity to combine the data sets to provide a more comprehensive view of this region of the placenta. As defects in the basal plate are, in part, at the root of the disease process, we believe that understanding the pathobiology that occurs in this region will increase our ability to alter the development and/or course of PE.

Granulysin activates antigen-presenting cells through TLR4 and acts as an immune alarmin

Granulysin (GNLY), an antimicrobial protein present in the granules of human cytotoxic T lymphocytes and natural killer (NK) cells, is produced as an intact 15-kDa form that is cleaved to yield a 9-kDa form. Alarmins are endogenous mediators that can induce recruitment and activation of antigen-presenting cells (APCs) and consequently promote the generation of immune response. We hypothesized that GNLY might function as an alarmin. Here, we report that both 9- and 15-kDa forms of recombinant GNLY-induced in vitro chemotaxis and activation of both human and mouse dendritic cells (DCs), recruited inflammatory leucocytes, including APCs in mice, and promoted antigen-specific immune responses upon coadministration with an antigen. GNLY-induced APC recruitment and activation required the presence of Toll-like receptor 4. The observed activity of recombinant GNLY was not due to endotoxin contamination. The capability of the supernatant of GNLY-expressing HuT78 cells to activate DC was blocked by anti-GNLY antibodies. Finally we present evidence that supernatants of degranulated human NK92 or primary NK cells also activated DCs in a GNLY- and Toll-like receptor 4-dependent manner, indicating the physiologic relevance of our findings. Thus, GNLY is the first identified lymphocyte-derived alarmin capable of promoting APC recruitment, activation, and antigen-specific immune response.

Changes of antimicrobial peptides and transepidermal water loss after topical application of tacrolimus and ceramide-dominant emollient in patients with atopic dermatitis

Increased transepidermal water loss (TEWL) and downregulated antimicrobial peptides (AMPs) are observed in patients with atopic dermatitis (AD). Tacrolimus and ceramide-dominant emollients are effective in the treatment of AD by preventing the production of inflammatory cytokines and by correcting skin barrier dysfunctions, respectively. Present study was designed to investigate the relationship between antimicrobial and barrier factors by measuring the changes of AMPs and TEWL after topical application of tacrolimus and ceramide-dominant emollient in the patients with AD. A total of three patients with AD were treated with tacrolimus in one lesion and ceramide-dominant emollient in another lesion for 4 weeks. RT-PCR and western blotting revealed that the mRNA and protein expression levels of hBD-2 and LL-37 were increased on the both study sites. Immunohistochemical analysis showed significant increase of AMPs and IL-1alpha, while, IL-4 was decreased on the both study sites. The mean changes of TEWL and AMPs showed no statistical difference between both sites. Tacrolimus and ceramide-dominant emollient influence on both TEWL and AMPs expression in patients with AD, namely they have similar effects on both of the two. This study shows that restoration of permeability barrier function is accompanied by the concomitant improvement of antimicrobial defense in patients with AD.

Blistering skin diseases: a bridge between dermatopathology and molecular biology

Although dermatopathology and molecular biology are often considered to be separate laboratory disciplines, the respective approaches are far from mutually exclusive. This is certainly the case for understanding the pathology of blistering skin diseases, both acquired and inherited. For example, in toxic epidermal necrolysis, dermatopathology in isolation may provide few clues to disease pathogenesis. There is widespread keratinocyte apoptosis and a variable infiltrate of cytotoxic T cells, but morphology alone offers little insight into what causes the epidermal destruction. In contrast, molecular biology studies have revealed several key processes that help explain the keratinocyte death, including increased expression of death receptors and their ligands on keratinocyte cell membranes as well as the presence of local or systemic immunocyte-derived cytolytic granules. For some inherited blistering diseases, however, such as epidermolysis bullosa, the molecular pathology is complex and difficult to unravel in isolation, yet the addition of dermatopathology is helpful in focusing molecular investigations. Notably, immunolabelling of cell adhesion proteins using specific antibody probes can identify reduced or absent immunoreactivity for candidate genes/proteins. Bridging dermatopathology and molecular biology investigations facilitates a greater understanding of disease processes, improves diagnostic accuracy, and provides a basis for the development and appraisal of new treatments.

Immunopathogenesis of psoriasis: focus on natural killer T cells

Psoriasis is a common inflammatory skin disease triggered by dysregulated immune response and characterized by hyperproliferation and altered differentiation of keratinocytes. Formation of psoriatic lesions is thought to be elicited by the complex cellular and cytokine network arising from the pathogenic interactions between keratinocytes and components of innate and acquired immune system. Natural killer T (NKT) cells are a heterogenous T-cell lineage that has been implicated in the pathogenesis of various autoimmune diseases including psoriasis. Due to the numerous functions of NKT cells that link innate and adaptive immunity, their role in psoriasis is complex and still elusive. We summarize the currently available literature data on this issue and discuss the possible role of NKT cells in the immunopathogenesis of this autoimmune disease.

Biology and clinical relevance of granulysin

Granulysin is a cytolytic and proinflammatory molecule first identified by a screen for genes expressed 'late' (3-5 days) after activation of human peripheral blood mononuclear cells. Granulysin is present in cytolytic granules of cytotoxic T lymphocytes and natural killer cells. Granulysin is made in a 15-kDa form that is cleaved into a 9-kDa form at both the amino and the carboxy termini. The 15-kDa form is constitutively secreted, and its function remains poorly understood. The 9-kDa form is released by receptor-mediated granule exocytosis. Nine kiloDalton granulysin is broadly cytolytic against tumors and microbes, including gram-positive and gram-negative bacteria, fungi/yeast and parasites. It kills the causative agents of both tuberculosis and malaria. Granulysin is also a chemoattractant for T lymphocytes, monocytes and other inflammatory cells and activates the expression of a number of cytokines, including regulated upon activation T cell expressed and secreted (RANTES), monocyte chemoattractant protein (MCP)-1, MCP-3, macrophage inflammatory protein (MIP)-1 alpha, interleukin (IL)-10, IL-1, IL-6 and interferon (IFN)-alpha. Granulysin is implicated in a myriad of diseases including infection, cancer, transplantation, autoimmunity, skin and reproductive maladies. Small synthetic forms of granulysin are being developed as novel antibiotics. Studies of the full-length forms may give rise to new diagnostics and therapeutics for use in a wide variety of diseases.

Skin peptides: biological activity and therapeutic opportunities

The skin provides an effective barrier to the loss of body fluids and environmental assault. In addition to the physical barrier provided by the stratum corneum, the skin also contains a chemical barrier consisting of antimicrobial peptides (AMPs), which control microbial growth on the surface. These AMPs also have multiple roles as mediators of inflammation with effects on epithelial and inflammatory cells, influencing cell proliferation, wound healing, cytokine/chemokine production and chemotaxis. This review describes the range of peptides found in the skin, both constitutive and those induced in response to injury. The role these peptides play in normal skin function and in various skin conditions is described. A better understanding of their role in normal and skin disease may offer new strategies in skin disease, dermatology and as cosmeceuticals.

Gene expression profiling of the human maternal-fetal interface reveals dramatic changes between midgestation and term

Human placentation entails the remarkable integration of fetal and maternal cells into a single functional unit. In the basal plate region (the maternal-fetal interface) of the placenta, fetal cytotrophoblasts from the placenta invade the uterus and remodel the resident vasculature and avoid maternal immune rejection. Knowing the molecular bases for these unique cell-cell interactions is important for understanding how this specialized region functions during normal pregnancy with implications for tumor biology and transplantation immunology. Therefore, we undertook a global analysis of the gene expression profiles at the maternal-fetal interface. Basal plate biopsy specimens were obtained from 36 placentas (14-40 wk) at the conclusion of normal pregnancies. RNA was isolated, processed, and hybridized to HG-U133A&B Affymetrix GeneChips. Surprisingly, there was little change in gene expression during the 14- to 24-wk interval. In contrast, 418 genes were differentially expressed at term (37-40 wk) as compared with midgestation (14-24 wk). Subsequent analyses using quantitative PCR and immunolocalization approaches validated a portion of these results. Many of the differentially expressed genes are known in other contexts to be involved in differentiation, motility, transcription, immunity, angiogenesis, extracellular matrix dissolution, or lipid metabolism. One sixth were nonannotated or encoded hypothetical proteins. Modeling based on structural homology revealed potential functions for 31 of these proteins. These data provide a reference set for understanding the molecular components of the dialogue taking place between maternal and fetal cells in the basal plate as well as for future comparisons of alterations in this region that occur in obstetric complications.

Granulysin-mediated tumor rejection in transgenic mice

Granulysin (GNLY) is a cytolytic molecule expressed by human CTL and NK cells with activity against a variety of tumors and microbes, including Mycobacterium tuberculosis. Although the molecular mechanism of GNLY-induced apoptosis of Jurkat T cells is well defined in vitro, no direct evidence for its in vivo effects has been demonstrated. Because there is no murine homologue of GNLY, we generated mice expressing GNLY using a bacterial artificial chromosome containing the human GNLY gene and its 5' and 3' flanking regions. GNLY is expressed in leukocytes from transgenic mice with similar kinetics as in PBMC from humans: GNLY is constitutively expressed in NK cells and, following stimulation through the TCR, appears in T lymphocytes 8-10 days after activation. Both forms of GNLY (9 and 15 kDa) are produced by activated T cells, whereas the 15-kDa form predominates in freshly isolated NK cells from transgenic animals. GNLY mRNA is highest in spleen, with detectable expression in thymus and lungs, and minimal expression in heart, kidney, liver, muscle, intestine, and brain. Allospecific cell lines generated from GNLY transgenic animals showed enhanced killing of target cells. In vivo effects of GNLY were evaluated using the syngeneic T lymphoma tumor C6VL. GNLY transgenic mice survived significantly longer than nontransgenic littermates in response to a lethal tumor challenge. These findings demonstrate for the first time an in vivo effect of GNLY and suggest that GNLY may prove a useful therapeutic modality for the treatment of cancer.

Coordinate expression of CC chemokine ligand 5, granulysin, and perforin in CD8+ T cells provides a host defense mechanism against Mycobacterium tuberculosis

The ability of CD8+ T cells to kill intracellular pathogens depends upon their capacity to attract infected cells as well as their secretion of cytolytic and antimicrobial effector molecules. We examined the Ag-induced expression of three immune effector molecules contained within cytoplasmic granules of human CD8+ T cells: the chemokine CCL5, the cytolytic molecule perforin, and the antimicrobial protein granulysin. Macrophages infected with virulent Mycobacterium tuberculosis triggered the expression of CCL5 in CD8+ T cells only in donors with previous exposure to the tuberculosis bacteria, not in naive donors. Functionally, CCL5 efficiently attracted M. tuberculosis-infected macrophages, but failed to exert direct antibacterial activity. Infected macrophages also triggered the expression of granulysin in CD8+ T cells, and granulysin was found to be highly active against drug-susceptible and drug-resistant M. tuberculosis clinical isolates. The vast majority of CCL5-positive cells coexpressed granulysin and perforin. Taken together, this report provides evidence that a subset of CD8+ T cells coordinately expresses CCL5, perforin and granulysin, thereby providing a host mechanism to attract M. tuberculosis-infected macrophages and kill the intracellular pathogen.

[Granulysin: antimicrobial molecule of innate and acquired immunity in human tuberculosis]

The recent global increase in cases of tuberculosis and the emergence of multidrug-resistant strains of tuberculosis have focused attention on the molecular mechanisms of human antimycobacterial immunity. The macrophage is not only the primary site for Mycobacterium tuberculosis growth but also ordinarily provides the primary lines of host defense against invading pathogens in its role as an effector of innate immunity. The ability of M. tuberculosis to survive and replicate in the host macrophage is critical to its pathogenesis, emphasizing a need for a clearer understanding of its interactions with the host macrophage. Macrophages use varied strategies to kill and destroy invading organisms, including production of reactive nitrogen and oxygen intermediates, phagosome maturation and acidification, fusion with lysosomes, exposure to defensins and host cell apoptosis. In human, granulysin is a recently identified antimicrobial protein expressed on cytotoxic T cells, natural killer (NK) cells and NKT cells. It has been shown that granulysin contributes to the defense mechanisms against mycobacterial infection. We hypothesized that human macrophages may possess antimicrobial substances, such as granulysin, and play a role in the defense mechanism.