Phenotype, activation and lymphokine secretion by gamma/delta T lymphocytes from schistosomiasis and carcinoma of the urinary bladder

Recruitment of Neutrophils Mediated by Vγ2 γδ T Cells Deteriorates Liver Fibrosis Induced by Schistosoma japonicum Infection in C57BL/6 Mice

Conventional adaptive T cell responses contribute to the pathogenesis of Schistosoma japonicum infection, leading to liver fibrosis. However, the role of gamma-delta (γδ) T cells in this disease is less clear. γδ T cells are known to secrete interleukin-17 (IL-17) in response to infection, exerting either protective or pathogenic functions. In the present study, mice infected with S. japonicum are used to characterize the role of γδ T cells. Combined with the infection of S. japonicum, an extremely significant increase in the percentage of neutrophils in the CD45⁺ cells was detected (from approximately 2.45% to 46.10% in blood and from 0.18% to 7.34% in spleen). Further analysis identified two different γδ T cell subsets that have different functions in the formation of granulomas in S. japonicum-infected mice. The Vγ1 T cells secrete gamma interferon (IFN-γ) only, while the Vγ2 T cells secrete both IL-17A and IFN-γ. Both subtypes lose the ability to secrete cytokine during the late stage of infection (12 weeks postinfection). When we depleted the Vγ2 T cells in infected mice, the percentage of neutrophils in blood and spleen decreased significantly, the liver fibrosis in the granulomas was reduced, and the level of IL-17A in the serum decreased (P < 0.05). These results suggest that during S. japonicum infection, Vγ2 T cells can recruit neutrophils and aggravate liver fibrosis by secreting IL-17A. This is the first report that a subset of γδ T cells plays a partial role in the pathological process of schistosome infection.

Gamma delta T cells in non-immune patients during primary schistosomal infection

The mevalonate pathway is critical for the survival of Schistosoma. γδ T cells, a small subset of peripheral blood (PB) T cells, recognize low molecular weight phosphorylated antigens in the mevalonate pathway, which drive their expansion to exert protective and immunoregulatory effects. To evaluate their role in schistosomiasis, we measured γδ T cells in the PB of non-immune travelers who contracted Schistosoma hematobium or Schistosoma mansoni in Africa. The maximal level of γδ T-cells following infection was 5.78 ± 2.19% of the total T cells, versus 3.72 ± 3.15% in 16 healthy controls [P = 0.09] with no difference between S. hematobium and S. mansoni in this regard. However, among the nine patients in the cohort who presented with acute schistosomiasis syndrome (AS), the level (3.5 ± 1.9%) was significantly lower than in those who did not (8.6 ± 6.4%, P < 0.05), both before and after therapy. Furthermore, γδ T cells increased significantly in response to praziquantel therapy. In a patient with marked expansion of γδ T cells, most expressed the Vδ2 gene segment, a hallmark of cells responding to cognate antigens in the mevalonate pathways of the parasite or the human host. These results suggest an immunoregulatory role of antigen responsive γδ T cells in the clinical manifestations of early schistosomal infection.

Gamma interferon secretion by human Vgamma2Vdelta2 T cells after stimulation with antibody against the T-cell receptor plus the Toll-Like receptor 2 agonist Pam3Cys

Circulating Vgamma2Vdelta2 T-cell populations in healthy human beings are poised for rapid responses to bacterial or viral pathogens. We asked whether Vgamma2Vdelta2 T cells use the Toll-like receptor (TLR) family to recognize pathogen-associated molecular pattern molecules and to regulate cell functions. Analysis of expanded Vgamma2Vdelta2 T-cell lines showed the abundant presence of TLR2 mRNA, implying that these receptors are important for cell differentiation or function. However, multiple efforts to detect TLR2 protein on the cell surface or in cytoplasmic compartments gave inconsistent results. Functional assays confirmed that human Vgamma2Vdelta2 T cells could respond to the TLR2 agonist (S)-(2,3-bis(palmitoyloxy)-(2RS)-propyl)-N-palmitoyl-(R)-Cys-(S)-Ser(S)-Lys4-OH trihydrochloride (Pam3Cys), but the response required coincident stimulation through the gammadelta T-cell receptor (TCR). Dually stimulated cells produced higher levels of cytoplasmic or cell-free gamma interferon and showed increased expression of the lysosome-associated membrane protein CD107a on the cell surface. A functional TLR2 that requires coincident TCR stimulation may increase the initial potency of Vgamma2Vdelta2 T-cell responses at the site of infection and promote the rapid development of subsequent acquired antipathogen immunity.

Human gamma delta T cells induce dendritic cell maturation

gamma delta T cells are known to be involved in the innate immune defenses against infectious microorganisms. Herein, we considered that gamma delta T cells could also influence adaptative immunity by interacting with dendritic cells (DC) in the early phase of the immune response. To investigate this hypothesis, gamma delta T cells isolated from the peripheral blood of healthy volunteers were cocultured with autologous monocyte-derived dendritic cells, which were subsequently analyzed for their expression of key surface molecules and for their production of IL-12. First, we found that gamma delta T cells induced the upregulation of HLA-DR, CD86, and CD83 on DC. This effect did not require cell to cell contact and could be blocked by a neutralizing anti-TNF antibody. We then observed that gamma delta T cells activated by the synthetic phosphoantigen bromohydrin pyrophosphate (BrHPP) induced the production of IL-12 (p40) and IL-12 (p70) by DC, an effect that involved IFN-gamma production. The relevance of this finding to DC function was demonstrated by the increased production of IFN-gamma by alloreactive T cells when stimulated in a mixed leucocyte reaction with DC preincubated with activated gamma delta T cells. We conclude that gamma delta T cell activation might result in DC maturation and thereby in enhanced alpha beta T cell responses.

Murine schistosomiasis mansoni: coordinate cytokine regulation and differences in cellular immune responses of granuloma cells and splenocytes to endogenous and exogenous schistosome egg antigens

To better understand the cellular immune mechanisms that regulate granulomatous inflammation to Schistosoma mansoni ova, we examined the dynamics of lymphocyte proliferation and cytokine expression by granuloma cells and splenocytes to endogenous and exogenous schistosome egg antigen (SEA) 6-19 weeks postinfection. Compared to splenocytes, granuloma cells (partially CD4+ cells) which are at the site of antigen release were highly activated by endogenous SEA and terminally differentiated as indicated by the more than 10-fold greater frequency of ex vivo interleukin (IL)-4, IL-5 and interferon (IFN)-gamma -secreting cells, greater levels of constitutive cytokine production and failure to proliferate to either endogenous or exogenous SEA. Endogenous cytokine production by granuloma cells was coordinately regulated, enhanced little by exogenous SEA, and temporally correlated with granulomatous inflammation. By contrast, CD4+ splenocytes produced comparatively little cytokine release by endogenous antigen, whereas exogenous SEA strongly induced IL-4, IL-5, IL-10 and IFN-gamma production and lymphocyte proliferation that correlated poorly with the dynamics of granulomatous inflammation. These results show that cytokine responses to endogenous SEA correlated better with granulomatous inflammation than responses to exogenous SEA. Furthermore, granuloma cells and splenocytes demonstrated strikingly different proliferative responses and dynamics of cytokine expression, suggesting that how SEA reactive lymphocytes traffic between lymphoid tissues and the granuloma is critical to a better understanding of the mechanisms of granulomatous inflammation and its modulation.

Molecular and functional characterization of chicken IL-15

A cDNA encoding chicken interleukin-15 was cloned from a CD4+ T cell hybridoma expression library by screening with a rabbit antibody against a protein fraction of conditioned medium containing T cell growth promoting activity. The chicken IL-15 cDNA contains an open reading frame of 143 amino acids with a single potential N-linked glycosylation site. The predicted m.w. of the encoded protein (16 kDa) matched the size of an immunoreactive band on Western blots of E. coli expressing the recombinant IL-15. Amino acid and nucleotide sequence analyses of chicken IL-15 revealed 31% and 46% identity with bovine IL-15 respectively and lesser homologies to other mammalian IL-15s. Chicken IL-15 contained all 4 highly conserved cysteine residues present in mammalian IL-15 sequences. RT-PCR demonstrated that the chicken IL-15 gene is expressed in many tissues including spleen, intestine, and muscle and in established macrophage, T lymphoma and fibroblast cell lines. Activation of spleen cells with Con A enhanced the expression of IL-15 gene transcripts in a time-dependent manner. CHO-K1 cells transfected with the chicken IL-15 cDNA secreted a biologically active protein supporting the growth of Con A activated spleen lymphocytes. Continuous culture of spleen Con A lymphoblasts with chicken IL-15 over two months resulted in an enriched T lymphocyte population expressing the gammadeltaTCR, CD8alpha, and CD3 cell surface antigens.

Donor γδ T Lymphocytes Promote Allogeneic Engraftment Across the Major Histocompatibility Barrier in Mice

T cells that express the αβ T-cell receptor are thought to be the T-cell population primarily responsible for facilitating alloengraftment. The role of γδ+ T cells that comprise only a minority of mature T cells in promoting allogeneic engraftment, however, has not been extensively studied. The purpose of this study was to determine whether γδ T cells were capable of facilitating alloengraftment in murine recipients of major histocompatibility complex-mismatched marrow grafts. We developed a model where engraftment of C57BL/6 × 129/F2 (H-2b) marrow in sublethally irradiated (800 cGy) recipients (AKR/J, H-2k) is dependent on the presence of mature donor T cells in the marrow graft. In this model, donor T-cell engraftment was significantly augmented by as few as 1 × 105 αβ T cells. The role of γδ T cells was then investigated using transgenic donors (C57BL/6 × 129 background) in which a portion of the T-cell receptor–β chain gene was deleted by gene targeting so that these mice lack αβ T cells. Addition of 10 × 106 naive γδ T cells to T-cell depleted marrow grafts was required to significantly increase alloengraftment, although donor T cells averaged <50% of total splenic T cells. To determine whether higher doses of γδ T cells would improve donor engraftment and eradicate residual host T cells, γδ T cells were ex vivo expanded with a γδ T-cell–specific monoclonal antibody and interleukin-2 and then transplanted into irradiated recipients. Transplantation of ≥ 160 × 106 activated γδ T cells was necessary to consistently and significantly augment donor cell chimerism and enhance hematopoietic reconstitution when compared to control mice, but host T cells persisted in these chimeras. Addition of 2.5 × 104 mature αβ T cells, which alone were incapable of facilitating engraftment, to T-cell depleted marrow grafts containing 160 × 106 activated γδ T cells resulted in long-term (<100 day) complete donor engraftment, indicating that limiting numbers of αβ T cells were required in the marrow graft for the eradication of residual host T cells. Using serial weight curves and B-cell reconstitution as end points, clinically significant graft-versus-host disease was not observed in these chimeras under these experimental conditions. These data show that, whereas less potent than αβ T cells, γδ T cells are able to promote engraftment and enhance hematopoietic reconstitution in allogeneic marrow transplant recipients.

T cells expressing the gamma delta T cell receptor are not required for egg granuloma formation in schistosomiasis

Immunopathology in schistosomiasis consists of a granulomatous response around parasite eggs. It has been established that granuloma formation is mediated by CD4+ T helper cells. However, the role of T cells bearing the gamma delta T cell receptor (TCR) has not been determined. In this study we utilized mutant mice that lack either alpha beta or gamma delta T cells as a result of gene targeting to investigate the relative roles of alpha beta and gamma delta T cells in the induction of immunopathology related to schistosomiasis. Mutant and control mice were infected with Schistosoma mansoni and granuloma formation as well as lymph node cell proliferative responses to egg antigens were analyzed after 8 weeks. TCR delta mutant mice (lacking gamma delta T cells) displayed vigorous formation of egg granulomas that were not significantly different from those observed in normal controls, both in terms of granuloma size and cellular composition. In contrast, TCR alpha and TCR beta mutant mice (lacking alpha beta T cells) were unable to form granulomas. Moreover, mesenteric lymph node cells from TCR delta mutant and control mice responded strongly to egg antigens in vitro, while TCR alpha and beta mutant mice did not. Our studies show that in schistosomiasis granuloma formation and proliferative responses to egg antigens are strictly dependent on alpha beta T cells. They also suggest that gamma delta T cells by themselves can neither mediate a granulomatous inflammation, nor significantly modify one mediated by alpha beta T cells.

Multiple labeling using two-color immunofluorescence with only one light source, two fluorescence photomultiplier tubes, and two light scatter detectors

Multiple labeling is necessary for the detailed phenotyping of cells in many biological systems in human and animal species. In a previous report, we described an approach permitting the study of three labels simultaneously by using the two-color immunofluorescence and one light source (Mansour et al., Cytometry 11:636-641, 1990). This approach allowed enumeration of cell subpopulations positive for only one label and negative for many others (X+ A- B- ...). We here present an improvement of the previous approach to allow analysis of double positive phenotypes (X+ Y+ A- B- ...), using only two fluorescence photomultiplier tubes and light scatter detectors. It consists of a two-step analysis that does not require additional material than that used in the former technique. Briefly, all antibodies are conjugated to only two fluorochromes: either FITC or PE. For the analysis of the X+ Y+ A- B- ... phenotype, the Y, A and B labels are all coupled to the same dye (FITC, e.g.) and the X label to the other dye (i.e, PE). In a first step, cells are labeled with X, A, and B, and in a second step, the second positive (Y) label is added. Two examples are supplied: CD56+ CD2+ CD3- CD16- decidua infiltrating cells and CD3+ TCR delta+ CD4- CD8- peripheral blood lymphocytes. This technique is useful for qualitative as well as quantitative analysis, with cytometers that do not have the appropriate hardware to do true three-color immunofluorescence analysis.

V gamma gene usage in peripheral blood gamma delta T cells

The majority (50-90%) of gamma delta T cells in the peripheral blood of adult individuals expresses a T-cell receptor (TCR) which uses V gamma 9 and V delta 2 as variable elements. Little is known about the distribution of other V gamma gene elements in the remaining 10-50% of gamma delta T cells. Here we have studied the V gamma gene expression in peripheral blood gamma delta T cells by 3-color flow cytometry analysis applying established monoclonal antibodies (mAb) directed against V gamma 9 and V gamma 4, as well as a novel mAb directed against V gamma 2, V gamma 3 and V gamma 4. On average, 79.9% of gamma delta T cells expressed V gamma 9, 11.9% V gamma 2/V gamma 3, 4.4% V gamma 4, and 7.5% one of the remaining V gamma 5, V gamma 8, V gamma 10 or V gamma 11 elements. There were remarkable variations in the gamma delta subset composition between individual donors. The majority (69.8%) of V gamma 2/V gamma 3/V gamma 4-bearing cells co-expressed V delta 1, while on average only 17.8% of V gamma 2/V gamma 3/V gamma 4-bearing cells co-expressed V delta 2. This is in contrast to V gamma 9-bearing gamma delta T cells, of which 83.1% used V delta 2 and only 12.7% V delta 1. Taken together, this data identifies V gamma 2/V gamma 3 as the second most frequently used set of V gamma elements in human peripheral blood gamma delta T cells.

A high proportion of the V delta 1+ synovial fluid gamma delta T cells in juvenile rheumatoid arthritis patients express the very early activation marker CD69, but carry the high molecular weight isoform of the leucocyte common antigen (CD45RA)

We have previously shown that gamma delta T cells in the synovial compartment of patients with juvenile rheumatoid arthritis (JRA) express activation antigens (CD69 and HLA-DR) and that they are predominantly of the V delta 1 subset. In this study we have analysed the expression of activation antigens (CD69 and HLA-DR) and different isoforms of the leucocyte common antigen (CD45RO and CD45RA) on the V delta 1 and the V delta 2 subsets of gamma delta T cells in paired samples of synovial fluid and peripheral blood of nine patients with JRA, and in the peripheral blood of five children with idiopathic scoliosis. In the synovial fluid of children with JRA, there were significantly more V delta 1+CD69+ and V delta 2+CD69+ cells compared with the peripheral blood of the same patients. In contrast, however, in the synovial fluid the V delta 1 and the V delta 2 subsets differed with respect to the expression of the two isoforms of the leucocyte common antigen. The majority of the V delta 1+ cells expressed the high molecular weight isoform (CD45RA+) while most of the V delta 2+ cells carried the low molecular weight variant (CD45RO+) of this molecule.