Repertoire development and ligand specificity of murine TCR gamma delta cells

γδ T cells: origin and fate, subsets, diseases and immunotherapy

The intricacy of diseases, shaped by intrinsic processes like immune system exhaustion and hyperactivation, highlights the potential of immune renormalization as a promising strategy in disease treatment. In recent years, our primary focus has centered on γδ T cell-based immunotherapy, particularly pioneering the use of allogeneic Vδ2+ γδ T cells for treating late-stage solid tumors and tuberculosis patients. However, we recognize untapped potential and optimization opportunities to fully harness γδ T cell effector functions in immunotherapy. This review aims to thoroughly examine γδ T cell immunology and its role in diseases. Initially, we elucidate functional differences between γδ T cells and their αβ T cell counterparts. We also provide an overview of major milestones in γδ T cell research since their discovery in 1984. Furthermore, we delve into the intricate biological processes governing their origin, development, fate decisions, and T cell receptor (TCR) rearrangement within the thymus. By examining the mechanisms underlying the anti-tumor functions of distinct γδ T cell subtypes based on γδTCR structure or cytokine release, we emphasize the importance of accurate subtyping in understanding γδ T cell function. We also explore the microenvironment-dependent functions of γδ T cell subsets, particularly in infectious diseases, autoimmune conditions, hematological malignancies, and solid tumors. Finally, we propose future strategies for utilizing allogeneic γδ T cells in tumor immunotherapy. Through this comprehensive review, we aim to provide readers with a holistic understanding of the molecular fundamentals and translational research frontiers of γδ T cells, ultimately contributing to further advancements in harnessing the therapeutic potential of γδ T cells.

Becoming aware of γδ T cells

The discovery that B cells and αβ T cells exist was predictable: These cells gave themselves away through their products and biological effects. In contrast, there was no reason to anticipate the existence of γδ T cells. Even the accidental discovery of a novel TCR-like gene (later named γ) that did not encode TCR α or β proteins did not immediately change this. TCR-like γ had no obvious function, and its early expression in the thymus encouraged speculation about a possible role in αβ T cell development. However, the identification of human PBL-derived cell-lines which expressed CD3 in complex with the TCR-like γ protein, but not the αβ TCR, first indicated that a second T cell-type might exist, and the TCR-like γ chain was observed to co-precipitate with another protein. Amid speculation about a possible second TCR, this potential dimeric partner was named δ. To determine if the δ protein was indeed TCR-like, we undertook to sequence it. Meanwhile, a fourth TCR-like gene was discovered and provisionally named x. TCR-like x had revealed itself through genomic rearrangements early in T cell development, and was an attractive candidate for the gene encoding δ. The observation that δ protein sequences matched the predicted amino acid sequences encoded by the x gene, as well as serological cross-reactivity, confirmed that the TCR-like x gene indeed encoded the δ protein. Thus, the γδ heterodimer was established as a second TCR, and the cells that express it (the γδ T cells) consequently represented a third lymphocyte-population with the potential of recognizing diverse antigens. Soon, it became clear that γδ T cells are widely distributed and conserved among the vertebrate species, implying biological importance. Consistently, early functional studies revealed their roles in host resistance to pathogens, tissue repair, immune regulation, metabolism, organ physiology and more. Albeit discovered late, γδ T cells have repeatedly proven to play a distinct and often critical immunological role, and now generate much interest.

Mitogenicity of bacterial lipopolysaccharide on the T lymphocyte population bearing the γδT cell receptor

In vitro [3H]-thymidine (TdR) uptake in T lymphocyte populations, taken and purified from proteose peptone-induced peritoneal exudate cells (PEC), spleens and thymuses of C3H/HeN mice, were investigated by stimulation with bacterial lipopolysaccharide (LPS). The T cells taken from PEC (PEC-T) were purified by passing them through a nylon fiber column (Nfc) and a G-10 column. They were then treated with anti-lak, anti-Mac-1 and anti-LR-1 antibodies plus complement (C). The PEC-T cells showed an increased [ 3H]-TdR uptake in response to LPS, while the splenic T cells and thymic T cells that had been purified and treated by a similar procedure with minor modifications, poorly responded to LPS and did not respond to LPS, respectively. The response of PEC-T to LPS was abolished when the PEC-T were pretreated with anti-Thy-1 or anti-γδ antibody plus C, but not αβ, T cell receptor (TCR) antibody plus C. The thymic T cells did not show any increase of [ H]-TdR uptake in response to LPS or anti-αβ or γδTCR antibody. However, obvious uptake did occur when the cells were stimulated with LPS and anti-γδTCR antibody, but not with anti-αβTCR antibody. IL-1 did not substitute for LPS in the response. These results suggest that LPS has a mitogenic ability to respond to a T cell population bearing γδTCR in PEC, and to a γδTCR-stimulated cell population in thymic cells. The difference in response to LPS between PEC-γδT and thymic γδT cells was discussed.

Gammadelta T cells: innately adaptive immune cells?

T cells employ a cell surface heterodimeric molecule, the T cell receptor (TCR), to recognize specific antigens (Ags) presented by major histocompatibility complex (MHC) molecules and carry out adaptive immune responses. Most T cells possess a TCR with an α and a β chain. However, a TCR constituted by a γ and a δ chain has been described, defining a novel subset of T cells. γδ TCRs specific for a wide variety of ligands, including bacterial phosphoantigens, nonclassical MHC-I molecules and unprocessed proteins, have been found, greatly expanding the horizons of T cell immune recognition. This review aims to provide background in γδ T cell history and function in mouse and man, as well as to provide a critical view of some of the latest developments on this still enigmatic class of immune cells.

Mechanisms determining cell membrane expression of different gammadelta TCR chain pairings

We investigated the ability of the most common TCR-gamma and delta chains to express on the cell surface. Vgamma1Cgamma4 and Vgamma7Cgamma1 chains paired with all TCR-delta chains tested, whereas Vgamma4Cgamma1 chains were found with Vdelta4 and Vdelta5, but not with Vdelta2 or Vdelta6 chains, and Vgamma2Cgamma2 chains were expressed only with Vdelta5. Mapping studies showed that up to four polymorphic residues influence the different co-expressions of Vgamma1 and Vgamma2 chains with Vdelta chains. Unexpectedly, these residues are not located in the canonical gamma/delta interface, but in the outer part of the gammadelta TCR complex exposed to the solvent. Expression of functional Vdelta4 or Vdelta6 chains in Vgamma2/Vdelta5(+) cells or of functional Vgamma2Cgamma2 in Vgamma1(+) cells reduced cell-surface expression of the gammadelta TCR. Taken together, these data show that (i) the Vgamma/Vdelta repertoire of mouse gammadelta T cells is reduced by physical constraints in their associations. (ii) Lack of Vgamma2/Vdelta expression is due to the formation of aberrant TCR complexes, rather than to an intrinsic inability of the chains to pair and (iii) despite not being expressed at the cell surface, the presence of a functionally rearranged Vgamma2 chain in gammadelta T cells results in reduced TCR levels.

γδ T cells: novel initiators of adaptive immunity

In this review, we discuss the potential role of human gammadelta T cells in the control of adaptive immunity. Our latest findings emerged as a consequence of our working hypothesis, which predicts a close relationship between the migration control in leukocytes and their function in immune processes as diverse as hematopoiesis, initiation of adaptive immunity, and immune surveillance in peripheral tissues. Leukocyte migration control is defined by the combination of migration and adhesion receptors on their surface and the tissue distribution of the corresponding ligands. According to our hypothesis, leukocytes featuring migration receptors for homing to lymph nodes (LNs) will also display activities that preferentially take place within LNs. Following this line of thought, by showing LN-homing properties in a subset of human gammadelta T cells, we speculated that gammadelta T cells influence the initiation of T- and B-cell responses. Here, we summarize our recent data, showing that LN-homing gammadelta T cells have potent antigen-presenting cell characteristics. This unexpected finding is discussed with regards to microbial sensing by human gammadelta T cells and a possible role for these cells in anti-microbial immunity.

Visualization of the earliest steps of γδ T cell development in the adult thymus

The checkpoint in gammadelta cell development that controls successful T cell receptor (TCR) gene rearrangements remains poorly characterized. Using mice expressing a reporter gene 'knocked into' the Tcrd constant region gene, we have characterized many of the events that mark the life of early gammadelta cells in the adult thymus. We identify the developmental stage during which the Tcrd locus 'opens' in early T cell progenitors and show that a single checkpoint controls gammadelta cell development during the penultimate CD4- CD8- stage. Passage through this checkpoint required the assembly of gammadelta TCR heterodimers on the cell surface and signaling via the Lat adaptor protein. In addition, we show that gammadelta selection triggered a phase of sustained proliferation similar to that induced by the pre-TCR.

Mechanisms controlling termination of V-J recombination at the TCRgamma locus: implications for allelic and isotypic exclusion of TCRgamma chains

Analyses of Vgamma-Jgamma rearrangements producing the most commonly expressed TCRgamma chains in over 200 gammadelta TCR(+) thymocytes showed that assembly of TCRgamma V-region genes display properties of allelic exclusion. Moreover, introduction of functionally rearranged TCRgamma and delta transgenes results in a profound inhibition of endogenous TCRgamma rearrangements in progenitor cells. The extent of TCRgamma rearrangements in these cells is best explained by a model in which initiation of TCRgamma rearrangements at both alleles is asymmetric, occurs at different frequencies depending on the V or J segments involved, and is terminated upon production of a functional gammadelta TCR. Approximately 10% of the cells studied contained two functional TCRgamma chains involving different V and Jgamma gene segments, thus defining a certain degree of isotypic inclusion. However, these cells are isotypically excluded at the level of cell surface expression possibly due to pairing restrictions between different TCRgamma and delta chains.

Rates of recombination and chain pair biases greatly influence the primary gammadelta TCR repertoire in the thymus of adult mice

Analyses of the rearrangement status of the TCRgamma and TCRdelta chain loci in progenies of individual gammadelta thymocytes showed a hierarchy of the different Vgamma and Vdelta gene segments to participate in a recombination reaction. Moreover, individual TCRgamma chains only pair efficiently with a variable number of TCRdelta chains. Interestingly, these two parameters are inversely correlated such that the TCRgamma and TCRdelta chains that rearrange more often show a higher level of restriction in their pairing capabilities. Our data suggest that these mechanisms, together with a natural variation affecting the expected frequencies at which rearrangement of different Vgamma gene segments give raise to functional TCRgamma chains, have coevolved to maximize the diversity of the gammadelta TCR repertoire minimizing the risk that a gammadelta T cell will express more than one TCR specificity at the cell surface, despite the fact that multiple TCRgamma rearrangements take place in the same progenitor cell.

Gamma interferon production by bovine gamma delta T cells following stimulation with mycobacterial mycolylarabinogalactan peptidoglycan

A large percentage of lymphocytes in the blood of cattle express the gamma delta T-cell receptor, but specific functions for these cells have not yet been clearly defined. There is evidence, however, that human, murine, and bovine gamma delta T cells have a role in the immune response to mycobacteria. This study investigated the ability of bovine gamma delta T cells to expand and produce gamma interferon (IFN-gamma) in response to stimulation with mycobacterial products. Bovine gamma delta T cells, isolated from the peripheral blood of healthy cattle, expanded following in vitro stimulation with live mycobacteria, mycobacterial crude cell wall extract, and Mycobacterium bovis culture filtrate proteins. In addition, purified gamma delta T cells, cocultured with purified monocytes and interleukin-2, consistently produced significant amounts of IFN-gamma in response to mycobacterial cell wall. The IFN-gamma-inducing component of the cell wall was further identified as a proteolytically resistant, non-sodium dodecyl sulfate-soluble component of the mycolylarabinogalactan peptidoglycan.

Most IL-4-producing gamma delta thymocytes of adult mice originate from fetal precursors

Thy-1(dull) gammadelta T cells constitute a distinct adult gammadelta T cell subset characterized by the expression of a TCR composed of Vgamma1Cgamma4 and Vdelta6Cdelta chains with limited junctional sequence diversity. However, several features of the expressed Thy-1(dull) TCR-gammadelta genes, in particular the absence or minimal presence of N region diversity and the almost invariable Ddelta2-Jdelta1 junction, are typical of rearrangements often found in the fetal thymus. In this study, we have investigated the origin of these cells. Few Thy-1(dull) gammadelta thymocytes developed in syngeneic radiation adult chimeras, regardless of whether the recipient mice were given adult bone marrow or fetal liver cells as a source of hemopoietic precursors. In contrast, normal numbers of Thy-1(dull) gammadelta T cells developed in fetal thymi grafted into adult syngeneic recipients. Interestingly, the majority of Thy-1(dull) gammadelta thymocytes present in the grafts were of graft origin, even when most conventional gammadelta and alphabeta thymocytes in the grafted thymi originated from T cell precursors of recipient origin. Single-cell PCR analyses of the nonselected TCR-gamma rearrangements present in adult Thy-1(dull) gammadelta thymocytes revealed that more than one-half of these cells represent the progenies of a limited number of clones that greatly expanded possibly during the first weeks of life. Finally, the second TCR-delta allele of a large number of Thy-1(dull) gammadelta T cells contained incomplete TCR-delta rearrangements, thus providing an explanation for the adult-type rearrangements previously found among nonfunctional V(D)J rearrangements present in Thy-1(dull) gammadelta thymocytes.

Premature expression of T cell receptor (TCR)alphabeta suppresses TCRgammadelta gene rearrangement but permits development of gammadelta lineage T cells

The T cell receptor (TCR)gammadelta and the pre-TCR promote survival and maturation of early thymocyte precursors. Whether these receptors also influence gammadelta versus alphabeta lineage determination is less clear. We show here that TCRgammadelta gene rearrangements are suppressed in TCRalphabeta transgenic mice when the TCRalphabeta is expressed early in T cell development. This situation offers the opportunity to examine the outcome of gammadelta versus alphabeta T lineage commitment when only the TCRalphabeta is expressed. We find that precursor thymocytes expressing TCRalphabeta not only mature in the alphabeta pathway as expected, but also as CD4(-)CD8(-) T cells with properties of gammadelta lineage cells. In TCRalphabeta transgenic mice, in which the transgenic receptor is expressed relatively late, TCRgammadelta rearrangements occur normally such that TCRalphabeta(+)CD4(-)CD8(-) cells co-express TCRgammadelta. The results support the notion that TCRalphabeta can substitute for TCRgammadelta to permit a gammadelta lineage choice and maturation in the gammadelta lineage. The findings could fit a model in which lineage commitment is determined before or independent of TCR gene rearrangement. However, these results could be compatible with a model in which distinct signals bias lineage choice and these signaling differences are not absolute or intrinsic to the specific TCR structure.

Characterization of an Avian (Gallus gallus domesticus) TCR αδ Gene Locus

Mammalian TCRδ genes are located in the midst of the TCRα gene locus. In the chicken, one large Vδ gene family, two Dδ gene segments, two Jδ gene segments, and one Cδ gene have been identified. The TCRδ genes were deleted on both alleles in αβ T cell lines, thereby indicating conservation of the combined TCRαδ locus in birds. Vα and Vδ gene segments were found to rearrange with one, both or neither of the Dδ segments and either of the two Jδ segments. Exonuclease activity, P-addition, and N-addition during VDJδ rearrangement contributed to TCRδ repertoire diversification in the first embryonic wave of T cells. An unbiased Vδ1 repertoire was observed at all ages, but an acquired Jδ1 usage bias occurred in the TCRδ repertoire. The unrestricted combinatorial diversity of relatively complex TCRγ and δ loci may contribute to the remarkable abundance of γδ T cells in this avian representative.

Why did your mother reject you? Immunogenetic determinants of the response to environmental selective pressure expressed at the uterine level

PROBLEM

Maternal "rejection" of the implanted conceptus is considered to account for a significant proportion of miscarriages (abortions) in both humans and animals. Our understanding of mechanisms has been limited, and hence, explanations for nonrejection have remained largely speculative. Losses, when they occur, could represent either random accidental failure of protective mechanisms or a more purposeful discrimination.

METHOD OF STUDY

An analysis of the most recent data.

RESULTS AND CONCLUSIONS

The embryo is most akin to a parasite, and pregnancy is most akin to a host-parasite interaction. If one excludes chromosome abnormalities in the embryo as a cause of death, activation of coagulation mechanisms, leading to vasculitis affecting the maternal blood supply to the implanted embryo, appears to represent a major loss-causing mechanisms--a form of ischemic autoamputation. Proinflammatory T-helper (Th) 1-type cytokines trigger this process via upregulation of a novel prothrombinase, fgl2. Th2/3 cytokines, such as interleukin (IL)-4, IL-10, and transforming growth factor (TGF)-beta 2, may antagonize the processes involved. Cytokine balance is determined by the genetics of the mother, which regulate her response to stress; endotoxin (LPS); and paternal antigens, selectively expressed on the trophoblast of the embryo, via imprinting. Based on studies in abortion-prone mice, where immunity to paternal alloantigens prevents loss, three distinct gene products in the embryo are proposed to determine the cytokine response to maternal lymphomyeloid cells in the uterus.

Kinetics of T cell receptor beta, gamma, and delta rearrangements during adult thymic development: T cell receptor rearrangements are present in CD44(+)CD25(+) Pro-T thymocytes

We performed a comprehensive analysis of T cell receptor (TCR) gamma rearrangements in T cell precursors of the mouse adult thymus. Using a sensitive quantitative PCR method, we show that TCRgamma rearrangements are present in CD44(+)CD25(+) Pro-T thymocytes much earlier than expected. TCRgamma rearrangements increase significantly from the Pro-T to the CD44(-)CD25(+) Pre-T cell transition, and follow different patterns depending on each Vgamma gene segment, suggesting that ordered waves of TCRgamma rearrangement exist in the adult mouse thymus as has been described in the fetal mouse thymus. Recombinations of TCRgamma genes occur concurrently with TCRdelta and D-Jbeta rearrangements, but before Vbeta gene assembly. Productive TCRgamma rearrangements do not increase significantly before the Pre-T cell stage and are depleted in CD4(+)CD8(+) double-positive cells from normal mice. In contrast, double-positive thymocytes from TCRdelta-/- mice display random proportions of TCRgamma rearranged alleles, supporting a role for functional TCRgamma/delta rearrangements in the gammadelta divergence process.

CD3 ligation on immature thymocytes generates antagonist-like signals appropriate for CD8 lineage commitment, independently of T cell receptor specificity

The signals that direct differentiation of T cells to the CD4 or CD8 lineages in the thymus remain poorly understood. Although it has been relatively easy to direct differentiation of CD4 single positive (CD4+) cells using combinations of antibodies and pharmacological agents that mimic receptor engagements, equivalent stimuli do not induce efficient maturation of CD8+ cells. Here we report that, irrespective of the MHC-restriction specificity of the TCR, differentiation of mature CD8+ thymocytes can be induced by ligation of CD3 polypeptides on immature thymocytes with a F(ab')2 reagent (CD3fos-F(ab')2). The tyrosine phosphorylation patterns stimulated by CD3fos-F(ab')2 have been shown to resemble those delivered to mature T cells by antagonist peptides, which are known to direct positive selection of CD8+ cells, and we can show that this reagent exhibits potent antagonistic-like activity for primary T cell responses. Our results suggest a distinction in the signals that specify lineage commitment in the thymus. We present a model of thymocyte differentiation that proposes that the relative balance of signals delivered by TCR engagement and by p56lck activation is responsible for directing commitment to the CD8 or CD4 lineages.

The alpha beta versus gamma delta T-cell lineage choice

During thymic development, immature T cells rearrange and express the genes encoding the T-cell antigen receptor and mature as either alpha beta or gamma delta lineage T cells. In the past year, advances have been made in understanding the role of individual components of the T-cell antigen receptor complex in the development of alpha beta and gamma delta lineage T cells. In addition, the transmembrane receptor Notch has recently been implicated as a new player in alpha beta versus gamma delta lineage determination.

CD8alphaalpha T cells in lesions of Listeria monocytogenes-infected beta2m-deficient mice

The beta2-microglobulin (beta2m)-deficient mutant mice lack alphabeta TCR CD8alphabeta T cells. We found markedly impaired granuloma formation in Listeria monocytogenes-infected beta2m-/- mice. Abundant CD8alphaalpha T cells were identified in loosely structured infiltrative liver lesions. Microfluorescence analysis disclosed that these CD8alphaalpha T cells expressed mostly the gammadelta TCR. CD8alphaalpha T cells were also found in the spleen of Listeria-infected beta2m-/- mice. These data provide first evidence for CD8alphaalpha T cells in listerial lesions of beta2m-/- mice.

Allospecific cytotoxic T cells generated from beta 2m-/- mice in primary MLC: analysis of activation requirements, specificity, and phenotype

It has been demonstrated by several investigators that beta 2m-/- knockout mice are deficient in the expression of MHC Class I molecules but can nevertheless generate CD8(+) allospecific cytotoxic T cells following vigorous in vivo priming. We demonstrate here that in vivo priming is not necessary to generate MHC Class I allospecific CTL from beta 2m-/- mice. When splenocytes from naive unprimed beta 2m-/- mice were provided exogenous cytokines in MHC Class I disparate primary MLC, allospecific cytolytic effectors were generated. beta 2m-/- MHC Class I allospecific CTL that were CD3+ and Thy1.2+ were otherwise heterogeneous in phenotype, including CD8+, CD4+, CD8-CD4-, TCR alpha beta+, and TCR gamma delta+ T cells. This phenotypic variability of beta 2m-/- CTL generated in primary MLC reveals the diversity of CTL precursors that develop in vivo in the absence of MHC Class I.

A prospective study of the immunophenotype and temporal changes in the histologic lesions of canine demodicosis

Mural folliculitis is a consistent histologic lesion of canine demodicosis. The objective of this study was to describe the immunophenotype and to evaluate temporal changes in histologic lesions of demodicosis during the course of therapy. Five dogs with demodicosis were examined and biopsied biweekly for up to 14 weeks; three dogs were evaluated once only. Lymphocyte subsets infiltrating the lesions were quantified using immunohistochemistry to detect CD3, CD21, CD4, and CD8 antigens. Lymphocyte subsets in blood were analyzed from four dogs using flow cytometry. Mural folliculitis was always present during clinically active disease. In contrast, following resolution of clinical lesions, perifolliculitis and/or perifollicular granulomas were present but mural folliculitis was absent. Most lymphocytes infiltrating the follicular epithelium in lesions of mural folliculitis were CD3+ and CD8+; the ratio of CD4+ :CD8+ cells in this epithelium was 0.032. In contrast, the perifollicular dermis contained approximately equal numbers of CD4+ cells and CD8+ cells, with slightly fewer CD21+B cells. In peripheral blood, the ratio of CD4+:CD8+ lymphocytes was reduced and the percentage of CD8+ cells was increased in three of four dogs. These results indicate that mural folliculitis is a consistent lesion of clinically active canine demodicosis and is characterized by infiltration of the follicular epithelium by CD3+ CD8+ T lymphocytes. These lymphocytes are cytotoxic T cells, which may mediate the injury to the follicular epithelium in demodicosis. Alternatively, CD8+ T cells may play a role in resistance to Demodex canis infection or may represent a deleterious immune response in dogs that develop demodicosis.

Isolation and phenotypic characterization of abomasal mucosal lymphocytes in the course of a primary Ostertagia ostertagi infection in calves

Isolation and characterization of surface marker phenotypes of abomasal intraepithelial (IEL), lamina propria (LPL) and abomasal lymph node lymphocytes (ABLN) from uninfected calves were conducted, and the dynamics of change in these populations during the course of a primary Ostertagia ostertagi infection were defined. To obtain viable IEL and LPL from the abomasal mucosa of cattle, a modified isolation method was developed. The phenotypic characterization of abomasal lymphocytes was accomplished by indirect immunofluorescence staining. In uninfected animals, numbers of T cells exceeded the number of immunoglobulin-bearing cells in IEL, LPL and ABLN. The predominant T cell type in IEL and LPL was CD8+ cells, while the CD4+ T cell predominated in ABLN. Levels of activated cells and T cell receptor-1 gamma delta T cells were higher in IEL and LPL compared to ABLN. Within 3 weeks of infection, the number of lymphocytes recovered from the abomasal lamina propira and the mass of the ABLN was dramatically increased when compared to uninfected animals. Laser flow cytometric analysis demonstrated increased levels of immunoglobulin-bearing cells, gamma delta T cells, and activated T cells in IEL, LPL and ABLN in the infected animals. The greatest changes in LPL and ABLN took place during the first days of infection, and these changes were apparent throughout the 28 days covered by the experiment.

Quercetin prevents UV-induced local immunosuppression, but does not affect UV-induced tumor growth in SKH-1 hairless mice

Ultraviolet is thought to induce skin tumors by its dual activity as a mutagenic agent and a suppressor of cell-mediated immunity. In the present study the effects of quercetin, a flavonoid-containing compound, on carcinogenesis and immunosuppression were studied in SKH hairless mice exposed to suberythemal doses of UV for up to 17 weeks. It was found that quercetin did not affect the onset or growth of non-melanoma skin tumors resulting from UV exposure. In contrast, it prevented the suppression in contact hypersensitivity (CHS) to picryl chloride induced by UV. The mechanism of this prevention might be explained by the observation that the decreased number of epidermal Langerhans' cells is partly prevented by the quercetin. Quercetin did not alter the effects of UV in increasing numbers of spleen and lymph node cells, only partly in decreasing the CD8-positive cells in spleen cell populations and decreasing the lymphoproliferative response of spleen cells to the mitogens concanavalin A and phytohemagglutinin. Thus oral quercetin did not prevent UV-induced carcinogenesis although it restored the skin-associated CHS response probably by protecting the antigen-presenting cells in the skin.

Notch activity influences the alphabeta versus gammadelta T cell lineage decision

The choice between the alphabeta or gammadelta T cell fates is influenced by the production of functional, in-frame rearrangements of the TCR genes, but the mechanism that controls the lineage choice is not known. Here, we show that T cells that are heterozygous for a mutation of the Notch1 gene are more likely to develop as gammadelta T cells than as alphabeta T cells, implying that reduced Notch activity favors the gammadelta T cell fate over the alphabeta T cell fate. A constitutively activated form of Notch produces a reciprocal phenotype and induces thymocytes that have functional gammadeltaTCR gene rearrangements to adopt the alphabeta T cell fate. Our data indicate that Notch acts together with the newly formed T cell antigen receptor to direct the alphabeta versus gammadelta T cell lineage decision.

A novel subset of adult gamma delta thymocytes that secretes a distinct pattern of cytokines and expresses a very restricted T cell receptor repertoire

We have characterized the function, phenotype, ontogenic development, and T cell receptor (TCR) repertoire of a subpopulation of gamma delta thymocytes, initially defined by expressing low levels of Thy-1, that represents around 5% and 30% of total gamma delta thymocytes in adult C57BL/6 and DBA/2 mice, respectively. Activation of FACS-sorted Thy-1dull gamma delta thymocytes from DBA/2 mice with anti-gamma delta monoclonal antibodies in the presence of interleukin-2 (IL-2) results in the secretion of high levels of several cytokines, including interferon-gamma (IFN-gamma), IL-4, IL-10, and IL-3. In contrast, only IFN-gamma was detected in parallel cultures of Thy-1bright gamma delta thymocytes. Virtually all Thy-1dull gamma delta thymocytes express high levels of CD44 and low levels of the heat-stable antigen and CD62 ligand, while around half of them express the NK1.1 marker. Thy-1dull gamma delta thymocytes are barely detectable in newborn animals, and their representation increases considerably during the first 2 weeks of postnatal life. The majority of Thy-1dull gamma delta thymocytes from DBA/2 mice express TCR encoded by the V gamma 1 gene and a novel V delta 6 gene named V delta 6.4. Sequence analysis of these functionally rearranged gamma and delta genes revealed highly restricted V delta-D delta-J delta junctions, and somewhat more diverse V gamma-J gamma junctions. We conclude that Thy-1dull gamma delta thymocytes exhibit properties that are equivalent to those of natural killer TCR alpha beta T cells. Both cell populations produce the same distinct pattern of cytokines upon activation, share a number of phenotypic markers originally defined for activated or memory T cells, display similar postnatal kinetics of appearance in the thymus and express a very restricted TCR repertoire.

Differential contribution of Lck and Fyn protein tyrosine kinases to intraepithelial lymphocyte development

The developmental stages and the role of protein tyrosine kinases (PTK) in the maturation of CD3+CD8 alpha alpha+ intraepithelial lymphocytes (IEL) have not been extensively characterized. However, comparisons of thymic and extrathymic T cell development indicate that these processes involve some distinct signaling and selection events. We used mice deficient in Lck, Fyn, or both Lck and Fyn to analyze the role that these src-family PTK play in IEL development. In contrast to thymocyte development, we found that all IEL subsets develop in mice deficient for either kinase alone. However, lck-/- animals exhibited reduced numbers of TcR alphabeta+ CD8alpha alpha+ IEL, indicating that Lck is important in the development of these cells. Mice which lack both Lck and Fyn fail to generate TcR alphabeta+ IEL, suggesting that signaling through the preTcR, mediated by Lck and, to a lesser extent Fyn, is required for maturation of all TcR alphabeta+ IEL lineages. Interestingly, a small population of TcR gammadelta+ CD8 alpha alpha+ cells are apparent in lck-/-fyn-/- animals, demonstrating that TcR alphabeta+ CD8 alpha alpha+ and TcR gammadelta+ CD8alpha alpha+ IEL have distinct PTK requirements for their development or expansion. CD3-CD8alpha- CD44+ and CD3-CD8alpha alpha+ CD16/32+ B220+ cells comprise the majority of IEL in both lck-/- fyn-/- and rag -/- mice, while they are poorly represented in wildtype controls. Comparison of the cell surface phenotype of these putative precursor IEL in lck-/- fyn-/- and rag-/- animals suggests that IEL maturation in these animals is arrested at an equivalent developmental stage. Overall, the data presented demonstrate that signals mediated by Lck or Fyn direct TcR alphabeta+ CD8alpha alpha+ IEL maturation but are dispensable for the development of TcR gammadelta+ CD8 alpha alpha+ IEL.

Autologous mixed leucocyte reaction and the polyclonal activation of bovine gamma/delta T cells

Bovine gamma/delta T cells proliferate in response to stimulation with gamma-irradiated autologous monocytes in the autologous mixed leukocyte reaction (AMLR). Flow cytometric analyses indicated that the proliferating cells included three major subpopulations of bovine gamma/delta T cells, distinguished by the differential expression of the gamma/delta T cell receptor epitopes N6 and N7. Interleukin-2 and acid-labile interferon were produced in AMLR cultures but the cultured cells did not lyse any of a large variety of target cells, including monocytes, allogeneic lymphoblasts, transformed bovine B cells (BL3), bovine fibroblast and the natural killer cell targets D17 and K562, even in the presence of lectins or after co-stimulation in the AMLR with antibodies to WC1, the gamma/delta T cell lineage-specific cell-surface differentiation antigen. Ex vivo gamma/delta T cells did not display lymphokine-activated killing whereas populations of peripheral blood mononuclear cells containing alpha/beta T cells did.

Selectively impaired development of intestinal T cell receptor gamma delta+ cells and liver CD4+ NK1+ T cell receptor alpha beta+ cells in T cell factor-1-deficient mice

T cell factor-1 (Tcf-1) is a transcription factor that binds to a sequence motif present in several T cell-specific enhancer elements. In Tcf-1-deficient (Tcf-1-/-) mice, thymocyte development is partially blocked at the transition from the CD4-8+ immature single-positive stage to the CD4+8+ double-positive stage, resulting in a marked decrease of mature peripheral T cells in lymph node and spleen. We report here that the development of most intestinal TCR gamma delta+ cells and liver CD4+ NK1.1+TCR alpha beta+ (NK1+T) cells, which are believed to be of extrathymic origin, is selectively impaired in Tcf-1-/- mice. In contrast, thymic and thymus-derived (splenic) TCR gamma delta+ cells are present in normal numbers in Tcf-1-/- mice, as are other T cell subsets in intestine and liver. Collectively, our data suggest that Tcf-1 is differentially required for the development of some extrathymic T cell subsets, including intestinal TCR gamma delta+ cells and liver CD4+ NK1+T cells.

Ontogenic development and tissue distribution of V gamma 1-expressing gamma/delta T lymphocytes in normal mice

A hamster monoclonal antibody (mAb) recognizing an epitope in the V gamma 1-J gamma 4-C gamma 4 chain of the gamma/delta T cell receptor has been generated. Using this mAb, we have quantitated the occurrence of V gamma 1-bearing gamma/delta T cells in the developing thymus and in the lymphoid organs and several epithelia of adult mice. The V gamma 1-expressing cells constitute a minor gamma/delta T cell subpopulation during fetal and early postnatal life, but they constitute a major population of gamma/delta T cells in the thymus and in the peripheral lymphoid organs in adult mice. In addition, we found that V gamma 1-bearing cells comprise a large proportion (15-60%) of the gamma/delta T cells present in the intestinal epithelium (i-IEL) in all strains of mice tested. V gamma 1+ i-IEL are present in athymic (nude) mice and in antigen-free mice, demonstrating that they can develop extrathymically and that their presence in the intestinal epithelium is independent of the antigenic load of the gut. Our results show that V gamma 1-bearing lymphocytes account for the largest population of gamma/delta T cells in the mouse. This population includes a thymus-dependent component that homes to the secondary lymphoid organs and a thymus-independent component that constitutes a major fraction of the gamma/delta i-IELs.

Murine autoimmune exocrinopathy: the minor salivary gland network shows a dichotomous pattern of histopathologic involvement

The minor salivary gland network of the MRL/l mouse was investigated in a kinetic study and compared with the major submandibular gland. We report that minor salivary glands adopt two mutually exclusive patterns of inflammatory lesions depending on the gland. The first pattern is characteristic of human Sjogren's syndrome. It developed during the second month, affected 89% of the animals over 20 weeks old, and consisted of an accumulation of mononuclear cells around the duct system. Only the anterior buccal gland (ABG) showed this pattern, which is shared by the major salivary glands. The ratio of CD4+ to CD8+ cells was the same in lesions and in healthy tissue. No neutrophils were found in these lesions. The second pattern affected all the minor salivary glands except the ABG. These lesions were never observed before the age of 20 weeks and affected 38% of MRL/l mice between the ages of 10-32 weeks. In this pattern, neutrophils were frequently found, but mainly gathered at the periphery of the gland lobules. That a systemic immunoregulatory defect may be expressed as two different patterns of histopathology in the minor salivary glands suggest that the network behaves as a dichotomous entity depending on particular microenvironmental influences.

Expression and regulation of adhesion molecules by gamma delta T cells from lymphoid tissues and intestinal epithelium

T cells bearing the gamma delta T cell receptor localize largely in epithelial tissues, but are also present at low frequency in organized secondary lymphoid organs. To assess the role of cell surface adhesion molecules in the traffic and tissue localization of gamma delta T cells, we compared the expression of these molecules on both alpha beta and gamma delta T cells in several lymphoid and non-lymphoid organs. In the gut epithelium, gamma delta cells express less LFA-1 (CD11a), Pgp-1 (CD44), and alpha 4 integrin than the corresponding alpha beta cells. In lymph nodes (LN) and Peyer's patches (PP), adhesion molecule expression by gamma delta cells is heterogeneous, with some of the cells having a phenotype similar to that of intraepithelial gamma delta cells and the rest expressing high levels of CD44 and L-selectin (CD62L) but lower beta 7 and alpha M290, a phenotype more like lymph node alpha beta cells. Therefore, the particular set of adhesion molecules expressed by a T cell is dependent, in part, on its anatomic location. Superimposed upon this, however, are differences in expression that are based on the type of T cell; LN and PP gamma delta T cells express less CD44 but much more beta 7, alpha M290 and ICAM-1 (CD54) than alpha beta T cells in the same organ. The differences in adhesion molecules between alpha beta and gamma delta cells are not due simply to differences in their activation status, because these molecules are regulated differently after activation through the T cell receptor (TcR)/CD3 complex. The differential expression of adhesion molecules on cells bearing a particular TcR V region suggests that distinct adhesion phenotypes may arise from prior contact with specific antigen and resultant cell activation in vivo. Lastly, the presence of high level expression of alpha 4 beta 7 and alpha M290 on L-selectinlo gamma delta cells in lymph nodes suggests that these gamma delta cells may be uniquely capable of migrating to the gut. The differences in adhesion molecule expression and regulation between gamma delta and alpha beta T cells could explain, in part, the distinct homing and tissue localization of these T cell subsets in vivo.

TCR gamma delta cells: mysterious cells of the immune system

Gamma delta cells participate in pathogenic infections and autoimmune conditions, yet, almost a decade after their discovery, little is known regarding their TCR repertoire or effector functions. Unlike MHC-restricted antigen recognition employed by TCR alpha beta cells, TCR gamma delta cells can recognize whole unprocessed antigens in an MHC- independent manner. The nature of positive and negative selection used to shape the repertoire of TCR gamma delta cells is unclear, especially in the nonlymphoid tissues where these cells predominate. While TCR gamma delta cells express an activated phenotype and are present in pathological conditions, their roles in immunological protein is unknown. This review will focus on our efforts to study these issues of TCR gamma delta biology.

An in vitro model for the expansion of V gamma 9 delta 2 T lymphocytes during development

The gamma/delta T lymphocytes represent a minority of T lymphocytes in human peripheral blood. Although there have been reports of reactivity against (myco-) bacterial antigens and heat shock proteins, their function and antigen specificity remain ill defined. The biological role of gamma/delta T cells has been related to functions within the 'first line of defense'. Similar to gamma/delta T lymphocytes in the T-cell compartment, CD5 positive B cells represent a small subset of B lymphocytes, which is thought to be involved in the maintenance of natural immunity and autoimmunity. We provide evidence for the cooperation of gamma/delta T cells and CD5 positive B cells in the proliferative response of gamma/delta T cells to bacterial antigens. Our data indicate a strong proliferation of V gamma 9 delta 2 T cells in response to gram-negative bacteria, which is dependent upon the presence of CD5 positive B-CLL or activated normal B lymphocytes. The selective stimulation of the V gamma 9 delta 2 subpopulation by gram-negative bacteria is also confirmed by analysis of different gamma/delta T-cell clones. The interaction of gamma/delta T cells with activated B cells and gram-negative bacteria may prove to be a useful model similar to the expansion of the V gamma 9 delta 2 subpopulation during development. In addition, our in vitro system should provide new insights in the interaction of CLL B cells with the immune system and the antigens recognized by gamma/delta T cells.

T cell receptor (beta chain) transgenic mice have selective deficits in gamma delta T cell subpopulations

TCR-beta (T cell receptor-beta chain) transgenic mice have altered lymphocyte development. TCR-beta transgenic mice are hyporesponsive to alloantigens in vivo and are deficient in gamma delta T cells. In order to begin a study of the relationship between a deficiency of alloreactive gamma delta cells and the defective function of in vivo alloantigen recognition, we analysed the gamma delta T cell development in TCR-beta mice. The presence of the TCR-V beta 8.2 chain transgene is associated with inhibition of gamma chain gene rearrangement. In order to determine how the presence of the TCR-beta transgene affects gamma delta T cell development, gamma delta T cells were studied in the skin, intestine and spleen. TCR-beta mice have dramatically reduced numbers of gamma delta T cells in the spleen and moderately reduced numbers of gamma delta T cells among intestinal intraepithelial lymphocytes. In contrast, these mice have normal numbers of gamma delta dendritic epidermal cells (DEC). These selective deficits could be due to the developmental regulation of transgene transcription during fetal life. We examined transcription of the TCR-beta transgene in the fetal thymus and found that the TCR-beta transgene is first transcribed at high levels on day 16 of fetal life, after DEC have already migrated from the thymus to the epidermis. Furthermore, mRNA from the transgene was detected in DEC, ruling out the formal possibility that DEC bear a gamma delta receptor only because they are incapable of expressing the transgene.(ABSTRACT TRUNCATED AT 250 WORDS)

Cytokine mRNA expression in skin in response to ectoparasite infection

Cellular infiltration and local cytokine mRNA levels were examined during the first 48 h of infection of skin by larvae of the sheep blowfly Lucilia cuprina. At the cellular level the response involved a dramatic influx of leucocytes (CD45+ cells). Among these infiltrating cells were large numbers of granulocytes, including neutrophils and eosinophils, as well as macrophage-like cells and lymphocytes. Many of the lymphocytes expressed cell surface markers characteristic of T cells including CD4, CD8 and the gamma delta TCR. The numbers of each of these cell types increased progressively as infection continued so that by 48 h the lesions were densely populated. Expression of mRNA for IL-6 could be detected by Northern blot analysis while mRNA for other inflammatory cytokines including IL-1 alpha, IL-1 beta, IL-8 and TNF alpha was detected using the polymerase chain reaction. Coincident with the influx of granulocytes and other cells there was an increase in the level of mRNA for the cytokines IL-1 alpha, IL-1 beta, IL-6 and IL-8. In the skin of the sheep there appeared to be constitutive expression of message for the cytokines IL-1 beta, IL-6 and TNF alpha, with the level of the latter not found to increase during the 48 h of infection examined. In situ hybridization was used to determine the location of IL-6 and TNF alpha mRNA within resting and infected skin. During infection, fibroblasts, macrophage-like cells and endothelium appeared to produce high levels of IL-6 mRNA. Expression of the T cell dependent cytokines IL-2 and IFN-gamma but not IL-4, increased in expression as time progressed and the population of infiltrating cells, including T cells, expanded.

Characteristics of fetal thymus-derived T cell receptor gamma delta intestinal intraepithelial lymphocytes

We have previously demonstrated that grafting of CBF1 (H-2b/d) fetal thymus (FTG) under the kidney capsule of congenitally athymic nude mice of BALB/c background (H-2d) generates a substantial number of T cell receptor (TCR) gamma delta intestinal intraepithelial lymphocytes (IEL) that were of FTG origin (H-2b+) (see accompanying report). Here we investigated the characteristics of these FTG-derived TCR gamma delta IEL and compared them to the extrathymically derived TCR gamma delta IEL found in nude mice. Phenotypically, FTG-derived TCR gamma delta IEL were similar to their extrathymically derived counterparts in that most were Thy-1-, CD5- and CD8 alpha alpha (homodimer). V gamma and V delta gene usage in thymus-derived and extrathymically derived TCR gamma delta IEL were found to be virtually the same. Functionally, FTG-derived TCR gamma delta IEL were similar to the TCR gamma delta IEL found in euthymic mice as both were relatively anergic to TCR cross-linking in vitro. However, FTG-derived TCR gamma delta IEL differed slightly from extrathymically derived TCR gamma delta IEL, which were completely nonresponsive to the same in vitro stimulation. Overall, these findings support the view that FTG-derived and extrathymically derived TCR gamma delta IEL are almost indistinguishable. Lastly, we demonstrate that despite their thymic origin, development of FTG-derived TCR gamma delta IEL partially takes place extrathymically; that is positive selection of FTG-derived V delta 4 IEL occurs extrathymically. In addition, we demonstrate that the CD8 molecule is not necessary for development and homing of FTG-derived TCR gamma delta IEL. This later finding suggests that the CD8 alpha alpha molecule develops extrathymically for FTG-derived CD8 alpha alpha TCR gamma delta IEL.

TL antigen as a transplantation antigen recognized by TL-restricted cytotoxic T cells

In contrast to broadly expressed classical class I antigens of the major histocompatibility complex, structurally closely related TL antigens are expressed in a highly restricted fashion. Unlike classical class I antigens, TL antigens are not known to be targets of cytotoxic T cells or to mediate graft rejection. Whereas classical class I antigens function as antigen-presenting molecules to T cell receptors (TCR), the role of TL is yet to be defined. To elucidate the function of TL, we have derived transgenic mice expressing TL in most tissues including skin by introducing a TL gene, T3b of C57BL/6 mouse origin, driven by the H-2Kb promoter. By grafting the skin of transgenic mice, we demonstrate that TL can serve as a transplantation antigen and mediate a TCR-alpha/beta+ CD8+ cytotoxic T cell response. This T cell recognition of TL does not require antigen presentation by H-2 molecules. Furthermore, we show that C57BL/6 F1 mice develop CD8+ T cells that are cytotoxic for C57BL/6 TL+ leukemia cells, providing further support for the concept that aberrantly expressed nonmutated proteins such as TL can be recognized as tumor antigens.

The gamma chain of the high-affinity receptor for IgE is a major functional subunit of the T-cell antigen receptor complex in gamma delta T lymphocytes

T-cell activation is a consequence of the clonotypic T-cell antigen receptor (TCR) binding to an antigen followed by signal transduction via the invariant subunits of the TCR/CD3 complex. gamma delta TCR cells are a small subset of T cells that populate both the epithelial and lymphoid tissues and have unique antigen specificity and function. However, the composition of invariant chains within the gamma delta TCR/CD3 complex has not been well characterized. Here we report that, unlike the majority of alpha beta T cell, gamma delta T cells isolated from spleen and intestinal epithelial tissue express high levels of the gamma chain of the high-affinity receptor for IgE (Fc epsilon RI gamma) as one invariant subunit of their TCR/CD3 complex. Fc epsilon RI gamma exists as both a homodimer and a heterodimer associated with the TCR zeta chain. Moreover, stimulation of the gamma delta TCR results in rapid tyrosine phosphorylation of Fc epsilon RI gamma. Our results suggest that utilization of distinct receptor signaling components may enable the coupling of antigen stimulation to the activation of different signal transduction pathways in alpha beta and gamma delta T cells.

Cytotoxic and interferon gamma-producing activities of gamma delta T cells in the mouse intestinal epithelium are strain dependent

We have analyzed the cytolytic activity of freshly isolated intraepithelial T cells (i-IEL) from the intestines of several different mouse strains in an anti-T-cell receptor monoclonal antibody-mediated redirected lysis assay. The cytolytic activity of gamma delta i-IEL but not that of alpha beta i-IEL was strain dependent. Mouse strains could be divided into high (H), marginal (M), and null (N) strains. The anti-gamma delta T-cell receptor monoclonal antibody-induced interferon gamma production showed the same strain-dependent variability, but the proliferative responses to gamma delta T-cell receptor crosslinking did not show this variability. The N phenotype of gamma delta i-IEL was found to be dominant in (H x N)F1 mice. In radiation bone-marrow chimeras the H/N phenotype was determined by the genotype of the reconstituting bone-marrow-derived cells but was not determined by the genotype of the radioresistant host cells. Analysis of (H x N)F1 backcross animals indicated that at least two genes are involved in determination of the H/N phenotype. One of these genes is major-histocompatibility-complex linked. No difference in the use of the variable region segment of the gamma-chain or delta-chain was seen between the gamma delta i-IEL from H and N strains. Various models that might explain the strain-dependent gamma delta i-IEL phenotypes are discussed.

Spinal fluid lymphocytes from a subgroup of multiple sclerosis patients respond to mycobacterial antigens

Immune responses to heat shock or stress proteins are observed in several chronic autoimmune diseases. Such proteins are major antigens of many bacteria, especially mycobacteria. To determine whether immune responses to stress proteins occur in chronic inflammatory diseases of the central nervous system such as multiple sclerosis (MS) we measured proliferative responses of lymphocytes from spinal fluids and bloods of patients with MS and other neurological diseases to a sonicate of M. tuberculosis, an acetone extract of M. tuberculosis, a recombinant 65-kd heat shock protein of M. leprae, and tetanus toxoid as a control recall antigen. Significantly increased spinal fluid lymphocyte responses to mycobacterial sonicate, relative to responses from paired peripheral blood lymphocytes, were present in 14 of 20 specimens from patients with MS (p < 0.025) and 2 of 9 specimens from patients with other neurological diseases. Spinal fluid lymphocytes also responded to tetanus toxoid, but differences between blood and spinal fluid were not statistically significant. Lymphocytes from 1 patient with MS responded only to M. leprae. There were no proliferative responses to the M. tuberculosis acetone extract. When patients with MS were classified according to duration of disease (< 2- or > 2-yr duration) 9 of 10 patients with recent onset had cerebrospinal fluid cells that responded to M. tuberculosis compared with 5 of 10 with longer duration symptoms (p < 0.012). Our data suggest a selective recruitment and/or expansion of mycobacterial reactive cells to the central nervous system of a subpopulation of patients with MS.(ABSTRACT TRUNCATED AT 250 WORDS)

Role of T-cell antigen receptors in rheumatic disease

The initiation and perpetuation of many rheumatic diseases is believed to be mediated by specific T-cells activated by an unknown antigenic peptide present on the surface of antigen presenting cells (APC). The T-cell antigen receptor (TCR) plays a central role in the recognition of antigen and subsequent T-cell activation. It is thought that a selective TCR repertoire may contribute to the immunopathogenesis of certain inflammatory rheumatic diseases. In this review recent progress in our understanding of TCR usage and their role in a variety of rheumatic diseases will be discussed. In addition, novel immunotherapeutic strategies based on a better understanding of the molecular mechanisms of antigen recognition will be reviewed.

An immunohistologic analysis of murine uterine T cells between birth and puberty

Murine uterine T cells were analysed on the basis of surface phenotype expression from birth to adulthood. T cells were rare in the uterus from birth until 2 weeks of age. In genetically immunocompetent mice, mature T cells expressing either TCR alpha/beta or TCR gamma/delta were first present as a major cell population at 3 weeks of age. The ratio of TCR alpha/beta to TCR gamma/delta was 1:1 at 3 weeks of age and this ratio did not change during sexual maturation. Almost all uterine T cells were CD8+ and the majority of these cells expressed CD8 alpha/beta rather than CD8 alpha/alpha. Cells expressing Thy1.2 were less frequent than cells expressing CD3 while cells expressing CD5 were rare. No major changes in T cell subsets occurred at puberty. Further, the microbial flora of the mice did not alter the time of appearance, frequency or subset distribution of uterine TCR+ cells. In the uteri of immunodeficient mice of genotype scid/scid TCR+ cells were found in low numbers and the initial appearance of TCR+ cells was delayed until 5 weeks of age.

Gamma delta T cells in human decidua

OBJECTIVE

Our purpose was to assess the presence and frequency of gamma delta T cells in the decidua of term and first-trimester pregnancies.

STUDY DESIGN

Term and first-trimester placentas were obtained from normal subjects. Frozen sections and cell suspensions were prepared from decidual tissue and stained with monoclonal antibodies to T cell markers. Cell sorter analysis was performed.

RESULTS

gamma delta T cells in term decidual cell preparations were enriched 2.4-fold compared with peripheral blood. Immunohistochemical staining of term decidual tissue demonstrated many gamma delta + and CD3+ T cells, fewer CD8+ cells, and rare CD4+ cells. In contrast, first-trimester decidua was found to be devoid of gamma delta + T cells, by both cell sorter analysis and immunohistochemical methods.

CONCLUSIONS

Term, but not early, decidua harbors a resident T-cell population that is significantly enriched in gamma delta T cells compared with blood. These lymphocytes may provide an added defense mechanism against infection during the peripartum.

Characterization of T cells expressing the gamma/delta antigen receptor in human renal allografts

To investigate the role of gamma/delta+ T cells in allograft rejection, we have studied the TCR phenotype and function of lymphocytes infiltrating rejecting, rejected, and nonrejecting human renal allografts. Two-color immunohistologic staining showed that 19% of rejecting biopsies and 40% of rejected nephrectomies had significant infiltration (> 10% of the total T-cell population) with gamma/delta+ T cells. No biopsies from nonrejecting kidneys showed > 10% gamma/delta+ T cells. Flow-cytometry analysis of T-cell populations expanded from rejecting and rejected allografts demonstrated that 33% of biopsy- and 40% of nephrectomy-derived populations had significant percentages (> 10%) of gamma/delta+ T cells. Six cell lines with increased numbers of gamma/delta+ T cells were tested for cytolytic activity against the NK target cell line K562 and compared with cytotoxic activity of exclusively alpha/beta T-cell populations. Lysis was noted by all gamma/delta+, but no gamma/delta-, populations. To confirm that the cytotoxicity of these gamma/delta+ T-cell populations was not MHC directed, one nephrectomy-derived population with 69% gamma/delta+ T cells by cytometry and > 50% by immunohistology was studied extensively. High levels of killing were seen against the NK targets K562 and Daudi as well as other malignant, benign, and third-party renal cell lines, but relevant alloantigen-expressing targets were not killed. Sterile cell sorting was used to isolate the gamma/delta+ T cells. The gamma/delta+ cells displayed enhanced killing of K562 while the gamma/delta- cells showed no cytolytic activity. Cytotoxicity mediated by gamma/delta+ T cells was also demonstrated against donor-derived, untransformed renal cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Secretion of a soluble, chimeric gamma delta T-cell receptor-immunoglobulin heterodimer

Soluble derivatives of T-cell antigen receptors (TCRs) should prove invaluable for studying the interaction of these receptors with antigens and major histocompatibility complex molecules, for structural studies, and for the identification of unknown ligands. We have engineered chimeric proteins, containing the extracellular domains of the mouse V gamma 1.1-C gamma 4 and V delta 6.2-C delta (V, variable; C, constant) TCR chains fused to the hinge region, CH2 (H, heavy), and CH3 domains of human IgG1 heavy chain, and expressed them by transient transfection in COS cells. We show here that TCR gamma-IgH and TCR delta-IgH chimeric chains are produced intracellularly in significant amounts, that the two chains can assemble correctly to form disulfide-linked, glycosylated heterodimers, and that a selective mechanism allows secretion of correctly paired receptor chains into the medium. Identity of the chimeric secreted TCR gamma delta-IgH heterodimer was confirmed by immunoblot analysis using V gamma 1-specific anti-peptide antiserum and immunoprecipitation analysis using the monoclonal antibody UC7, which is shown to be specific for the TCR delta chain. In addition, the soluble TCR gamma delta-IgH heterodimer can be immunoprecipitated with the anti-clonotypic monoclonal antibody F10/56, which suggests that the fusion protein likely has a structural conformation similar to that of the native TCR. The COS cell expression system may prove useful for the production of additional TCR-IgH fusion proteins.