A role for epithelial gamma delta T cells in tissue repair

Conclusions  A balance between epithelial growth and repair versus inflammation to isolate and contain damage is critical for maintenance of the epithelial microenvironment. Epithelial γδ T cells appear to play an important role in maintaining the integrity of the epithelial tissues they survey. Insult to the epithelium likely leads to the up-regulation of self-associated stress molecules that are recognized by intraepithelial γδ T cells. The limited, and in some cases canonical, repertoire of the epithelial γδ TCRs is certainly consistent with this recognition of damaged self, rather than recognition of the vast array of possible non-self antigens that could invade these epithelial barriers. Furthermore, the cellular context of the various γδ T cell subsets and the types of antigens they engage together may contribute to the distinct requirements of γδ T cells for PTKs in their selection, homing and presumably also in their response to epithelial cell damage.     

IL-17 and VEGF are necessary for efficient corneal nerve regeneration

The contribution of acute inflammation to sensory nerve regeneration was investigated in the murine cornea using a model of corneal abrasion that removes the stratified epithelium and subbasal nerve plexus. Abrasion induced accumulation of IL-17(+) CCR6(+) γδ T cells, neutrophils, and platelets in the cornea followed by full restoration of the epithelium and ～19% regeneration of sensory nerves within 96 hours. Mice deficient in γδ T cells (TCRδ(-/-)) or wild-type mice treated systemically with anti-IL-17 had >50% reduction in leukocyte and platelet infiltration and >50% reduction in nerve regeneration. Strategies used to prevent neutrophil and platelet accumulation (eg, wild-type mice treated with anti-Ly6G or anti-GP1bα antibody to deplete neutrophils or platelets) also resulted in >50% reductions in corneal nerve density. Infiltrating neutrophils and platelets stained positively for VEGF-A, tissue levels of VEGF-A peaked coincidentally with peak tissue levels of neutrophils and platelets, depletion of neutrophils before injury reduced tissue VEGF-A levels by >70%, and wild-type mice treated systemically with anti-VEGF-A antibody exhibited >80% reduction in corneal nerve regeneration. Given the known trophic effects of VEGF-A for neurite growth, the results in this report demonstrate a previously unrecognized beneficial role for the γδ T cell-dependent inflammatory cascade involving IL-17, neutrophils, platelets, and VEGF-A in corneal nerve regeneration.     

Distinct subpopulations of gamma delta T cells are present in normal and tumor-bearing human liver

Gamma delta T cells are thought to mediate immune responses at epithelial surfaces. We have quantified and characterized hepatic and peripheral blood gamma delta T cells from 11 normal and 13 unresolved tumor-bearing human liver specimens. gamma delta T cells are enriched in normal liver (6.6% of T cells) relative to matched blood (0.9%; P = 0.008). The majority express CD4(-)CD8(-) phenotypes and many express CD56 and/or CD161. In vitro, hepatic gamma delta T cells can be induced to kill tumor cell lines and release interferon-gamma, tumor necrosis factor-alpha, interleukin-2 and interleukin-4. Analysis of V gamma and V delta chain usage indicated that V delta 3(+) cells are expanded in normal livers (21.2% of gamma delta T cells) compared to blood (0.5%; P = 0.001). Tumor-bearing livers had significant expansions and depletions of gamma delta T cell subsets but normal cytolytic activity. This study identifies novel populations of liver T cells that may play a role in immunity against tumors.     

Tissue distribution of human gamma delta T cells: no evidence for general epithelial tropism.

In man and mice only a small proportion of T cells in the peripheral lymphoid compartment express the gamma delta T cell receptor (TCR). In mice, however, gamma delta T cells comprise the predominant population at particular epithelial sites--in epidermis and epithelia of intestine, reproductive organs, and tongue. The distribution of gamma delta T cells in normal human tissues was investigated, paying particular attention to epithelial layers. In all lymphatic organs and in epithelia of a wide variety of non-lymphatic organs, including the respiratory tract, male and female reproductive organs and tongue, gamma delta T cells constituted less than 5% of total T cells, with the remainder expressing TCR alpha beta. The only exception was the intestine, where gamma delta T cells were preferentially situated in the columnar epithelium of the crypts, rather than in the lamina propria. It is concluded, therefore, that human gamma delta T cells do not display a general epithelial tropism and are, in terms of relative numbers, no more able than alpha beta T cells to carry out continuous surveillance of the immune system against infection or transformation in epithelia. gamma delta T cells may, however, have a specialised function in the epithelium of the intestinal tract.     

T gamma delta cells in juvenile rheumatoid arthritis and rheumatoid arthritis. In the juvenile rheumatoid arthritis synovium the T gamma delta cells express activation antigens and are predominantly V delta 1+, and a significant proportion of these patients have elevated percentages of T gamma delta cells

Using the anti-TcR gamma/delta-1 monoclonal antibody and flow cytometry, we examined the number of T gamma delta cells in paired samples of peripheral blood and synovial fluid or tissue from 24 children with juvenile rheumatoid arthritis (JRA), five adult patients with JRA, and 14 patients with rheumatoid arthritis (RA). No significant difference was found in the synovial compartment T gamma delta values compared with the blood in JRA, adult JRA, or RA patients. Nor was any significant difference found in the peripheral blood or synovial compartment T gamma delta values in any of the three patient groups compared with the peripheral blood of normal controls. However, seven of the children with JRA had very high T gamma delta values in the synovial compartment while none of the normal children had high T gamma delta values in the blood (P = 0.02, Fisher's exact test). This may indicate a possible separate JRA patient group with high T gamma delta levels in the synovial compartment. In six JRA patients further analysed for T gamma delta subpopulations, a significant predominance of V delta 1+ cells was found in the synovial compartment compared with the corresponding peripheral blood samples (P less than 0.05, Wilcoxon's signed test) and with peripheral blood of child controls (P less than 0.05, Mann-Whitney U test). In these six patients, the T gamma delta-cell expression of the very early activation antigen CD69 were significantly higher (P less than 0.05, Wilcoxon's signed test) in the synovial compartment compared with the peripheral blood. Synovial T gamma delta cells expressing HLA-DR and interleukin 2 receptors could also be detected, in contrast to the peripheral blood in which no T gamma delta cells expressing these antigens could be found. These data suggest that the synovial T gamma delta cells had been activated in vivo.     

Is there a role for gamma delta T cells in malaria?

Peripheral blood lymphocytes of the V gamma 9+ family of gamma delta T cells proliferate vigorously in response to Plasmodium falciparum. In this brief article, Jean Langhorne and colleagues discuss this response and assess the possible role of gamma delta T cells in the pathogenesis of malaria.     

Roles of heat shock proteins and gamma delta T cells in inflammation

Elimination of activated inflammatory cells that infiltrate and damage host organs can reduce morbidity and mortality. A better understanding of the mechanisms by which these processes occur may lead to new approaches to prevent tissue damage. The lungs, gastrointestinal tract, and skin are particularly prone to infection and collateral damage by inflammatory cells. Specialized lymphocytes protect these organs from collateral tissue damage by eliminating neutrophils and macrophages from inflamed tissues. These lymphocytes recognize signals produced by inflammatory cells. One such signal is heat shock protein (Hsp) expressed on the cell surface of inflamed phagocytes. Mammalian Hsp molecules closely resemble their microbial equivalents, and therefore phagocytes decorated with these molecules are recognized as target cells. T lymphocytes bearing the gammadelta T cell receptor (TCR) elicit cytotoxic activity toward macrophages and neutrophils that express Hsp60 and Hsp70, respectively, protecting host organs from collateral tissue damage by phagocytes.     

Chitosan-coated alginate membranes for cultivation of limbal epithelial cells to use in the restoration of damaged corneal surfaces

Some chemicals or thermal burns may result in abnormal reepithelialization by conjunctival epithelial cells and it causes different types of damage on the cornea surface. When reepithelialization does not occur, chronic inflammation and neovascularization develop, often leading to stroma scarring and/or ulceration. The aim of this study is to restore the human corneal surface with autologous corneal epithelial sheets generated by serial cultivation of the limbal epithelial cells over the different compositions of composite membranes. The composite membranes were prepared by coating the alginate membrane with chitosan. In this method, alginate membrane was prepared by precipitation of the sodium alginate solution in calcium chloride solution. Alginate membranes were washed, dried and immersed into the chitosan solutions to prepare composite membranes. The composite membranes were characterized based on their morphology, hydrophilicity, swellability, and chemical structure. In the last part of the study, composite membranes were used as base matrices for limbal epithelial cell cultivation. The cell cultivation on polymeric membranes was investigated as the in vitro studies. In these studies cell attachment, spreading and growth on polymeric membranes were evaluated.     

Compartmentalization gamma/delta T cells and their putative role in mucosal immunity

gamma/delta T cells are an enigmatic group of cells and their functions still remain unknown. The epithelial-associated gamma/delta T cells, which are abundant at mucosal surfaces, are ideally situated to contribute to the initial stages of the immune response. Recent evidence suggests that they recognize stress-induced self-antigens which would enable a homogeneous population of gamma/delta T cells to monitor multiple insults to the epithelium. This could explain the observed oligoclonality and homogeneous distribution of cells carrying identical TCR within mucosal surfaces. However, the analysis of the TCR delta repertoire from different mucosal surfaces indicated that gamma/delta T cells are highly compartmentalized. Thus, gamma/delta T cells are not one homogeneous group of cells which recognize the same (stress-induced) self-antigens, but consist of different subsets that are likely to have distinct functions. It is possible that gamma/delta T cells interact with antigens that are specific for that organ or recognize foreign antigens which are limited to that site. In addition it was shown that gamma/delta T cells can have opposite functions and be proinflammatory or promote epithelial healing. This review focuses on the distribution and repertoire of mucosal gamma/delta T cells and discusses what is currently known about the functions of these cells. Furthermore, their potential role in inflammatory bowel disease is examined.     

Increase of gamma/delta T cells in hospital workers who are in close contact with tuberculosis patients.

gamma/delta T cells are likely to participate in the immune response to tuberculous infection in humans. In this study, we carried out an investigation to characterize the responsiveness of gamma/delta T cells from tuberculous patients and healthy individuals to mycobacterial stimulation in vitro. Healthy subjects were assigned to the following two groups: those who had been exposed to tuberculosis (contacts) and those who had not been exposed (noncontacts). The percent gamma/delta T cells in fresh peripheral blood obtained from health care workers who were tuberculin skin test positive and who had constant contact with patients with active tuberculosis (healthy contacts) was significantly higher, whereas healthy noncontacts showed the normal range of gamma/delta T cells. Patients with active pulmonary tuberculosis also had low levels of gamma/delta T cells. HLA-DR antigen-bearing activated gamma/delta T cells were observed in higher percentages among healthy contacts than among healthy noncontacts or patients with pulmonary tuberculosis. In healthy contacts, gamma/delta T cells increased as a percentage of peripheral blood mononuclear cells after in vitro stimulation with purified protein derivative (PPD) tuberculin compared with the percentage of fresh peripheral blood mononuclear cells that they made up, whereas no such increase was observed in patients with tuberculosis or in healthy noncontacts. Phenotypic analysis of the gamma/delta T cells in healthy contacts, which increased in number in vitro in response to PPD, revealed the preferential outgrowth of CD4+ V gamma 2+ gamma/delta T cells. This expansion of gamma/delta T cells by PPD required accessory cells, and it was inhibited by the addition of an antibody against HLA-DR in culture. Proteolytic digestion of PPD showed that gamma/delta T cells increased in number in response to peptide, but not nonpeptide, components of PPD. These findings suggest that gamma/delta T cells, especially CD4+ V gamma 2+ gamma/delta T cells, may participate in the immune surveillance of tuberculous infections in humans.     

T cell receptor gamma delta bearing cells are decreased in the peripheral blood of patients with atopic diseases.

The biological role of T cell receptor (TCR) gamma delta bearing cells is currently not fully understood. Recently, a monoclonal antibody (TCR delta 1) reacting against the whole molecule became available which facilitates the direct analysis of TCR-gamma delta+ cells. We studied 11 children with atopic dermatitis, 20 children with atopic asthma, 18 adults with atopic dermatitis and 38 healthy age matched controls aged 4-51 years. Lymphocytes were isolated from heparinized peripheral blood and the proportion of TCR-gamma delta+ lymphocytes was determined by FACS analysis. Patients with atopic diseases yielded a significantly (P less than 0.01) lower proportion of TCR-gamma delta+ cells compared with normal controls (median 4.8% versus 7.1%). The percentage of TCR-gamma delta+ cells showed an age-dependent decline in both the patient group (r = -0.49, P less than 0.01) and the control group (r = -0.40, P less than 0.01). In addition, the proportion of cells which expressed CD8, TCR-gamma delta or CD4, TCR-gamma delta simultaneously was determined by double labelling immunofluorescence. Whereas CD4+, TCR-gamma delta+ cells could be identified in only a few individuals, CD8+, TCR-gamma delta+ cells were found in nearly all controls (median 2.4%, range 0.0-10.8%); atopic patients displayed significantly (P less than 0.01) lower proportions of CD8+, TCR-gamma delta+ cells.     

Different roles are played by alpha beta and gamma delta T cells in acquired immunity to Chlamydia trachomatis pulmonary infection.

Using gene knockout and wild-type C57BL/6 mice, we examined the role of alpha beta and gamma delta T cells in the resolution of Chlamydia trachomatis mouse pneumonitis (MoPn) biovar pulmonary infection. The results show that alpha beta T-cell-deficient (alpha-/-) mice, when compared with wild-type control mice, have dramatically increased mortality rate and greater in vivo growth of MoPn. The alpha beta T-cell-deficient mice were as susceptible to MoPn infection as T- and B-lymphocyte-deficient (RAG-1-/-) mice. Moreover, both alpha beta T-cell-deficient and RAG-1 mutant mice failed to mount delayed-type hypersensitivity (DTH) responses to organism-specific challenge and showed undetectable interferon-gamma (IFN-gamma) production by spleen cells upon in vitro organism-specific restimulation. In contrast, gamma delta T-cell-deficient mice exhibited intact DTH responses and their mortality rate and in vivo chlamydial growth were comparable to those in wild-type controls. More interestingly, gamma delta T-cell-deficient mice showed significantly higher levels of IFN-gamma production than did wild-type mice. The data indicate that the alpha beta T cell is the major T-cell population for acquired immunity to chlamydial infection and that gamma delta T cells may play an ancillary role in regulating the magnitude of alpha beta T-cell responses.     

Flow cytometric analysis of gamma delta T cells and natural killer cells in HIV-1 infection.

We have previously shown that HIV-1 seropositivity is associated with an increase in the difference between the number of CD3+ lymphocytes and the total number of CD4+ and CD8+ lymphocytes [CD3 - (CD4 + CD8)] among peripheral blood lymphocytes (PBL). To investigate the cellular basis of this increase, PBL from seronegative (SN) and AIDS-free seropositive (SP) homosexual men and intravenous drug users were analyzed by two-color flow cytometry. Results showed that SP compared to SN manifested the expected elevation in calculated [CD3 - (CD4 + CD8)] cells (87 vs 28 cells/mm3; P less than 0.001). Only small differences in lymphocyte populations that could contribute to this increase were observed, namely lymphocytes expressing the CD3+CD4-CD8-phenotype (67 vs 56 cells/mm3; P greater than 0.10) or the CD8dim phenotype (135 vs 142 cells/mm3; P greater than 0.10). However, SP had significantly lower numbers of cells expressing the CD56+CD3- phenotype characteristic of natural killer cells (81 vs 170 cells/mm3; P less than 0.001) and significantly higher numbers of T cells expressing the gamma delta T cell receptor (TCR) (81 vs 62 cells/mm3; P = 0.10). The latter difference was primarily due to higher numbers of cells coexpressing gamma delta-TCR and low levels of CD8 (27 vs 15 cells/mm3; P = 0.009). These data suggest that HIV-1 seropositivity is associated with low numbers of natural killer cells and high numbers of CD8+ gamma delta-TCR lymphocytes. Changes in these populations may reflect altered host defense against HIV-1 or altered T cell kinetics in the presence of HIV-1 infection.     

Characterization of suppressor T cells for antibody production by chicken spleen cells. I. Antigen-induced suppressor cells are CT8+, TcR1+ (gamma delta) T cells.

Suppressor activity of chicken T cells has been previously defined in an in vitro assay of the secondary response of spleen cells to sheep erythrocytes. We have used this assay to examine the phenotype of the T-cell subpopulation(s) that is responsible for this activity. The suppressive effect was alleviated by removal of the TcR1+ (gamma delta) and CD8+ subpopulations, but was unaffected by the removal of the TcR2+ (alpha beta) and CD4+ cells. The addition of a histamine type 2 (H2) receptor antagonist, cimetidine, enhanced the antibody response in the presence of the suppressor cells. The data indicate that one type of T cells with suppressor capability expresses TcR1 and the CD8 accessory molecule, and that these cells may be influenced via H2 receptors.