Regulation of T cell-dependent autoantibody production by a gammadelta T cell line derived from lupus-prone mice

[Expression of gamma-delta T cells in immune microenvironment in children with Henoch-Schönlein purpura]

OBJECTIVE

To study the role of gamma-delta T (γδ T) cells and its subsets in the immunopathogenesis of Henoch-Schönlein purpura (HSP) in children, and to provide new ideas for the treatment of HSP in children from the aspect of γδ T cell regulation.

METHODS

A total of 33 children with HSP were enrolled as the HSP group, and 21 healthy children were enrolled as the healthy control group. The percentages of γδ T cells and its subsets Vδ1⁺ T and Vδ2⁺ T cells among peripheral blood mononuclear cells (PBMCs) were measured, as well as the apoptosis rate of γδ T cell and plasma level of interleukin-17 (IL-17).

RESULTS

Compared with the healthy control group, the HSP group had significantly lower percentages of lymphocytes in PBMCs and Vδ2⁺ T cells in γδ T cells (P<0.05). The HSP group had significantly higher percentage of Vδ1⁺ T cells in γδ T cells and plasma level of IL-17 than the healthy control group. The HSP group had a significantly higher overall apoptosis rate of γδ T cells than the healthy control group (P<0.05), especially early apoptosis. The percentage of Vδ2⁺ T cells was positively correlated with overall apoptosis rate (r_s=0.615, P<0.05) and was negatively correlated with IL-17 level (r_s=-0.398, P<0.05).

CONCLUSIONS

Vδ1⁺/Vδ2⁺ T cell immune imbalance mediated by γδ T cells and over-activation of IL-17 may be involved in the development of HSP, among which the disturbance of immune tolerance induced by Vδ2⁺ T cells plays an important role in the pathophysiology of the disease.

The mechanisms and applications of T cell vaccination for autoimmune diseases: a comprehensive review

Autoimmune diseases (ADs) are a spectrum of diseases originating from loss of immunologic self-tolerance and T cell abnormal autoreactivity, causing organ damage and death. However, the pathogenic mechanism of ADs remains unclear. The current treatments of ADs include nonsteroidal anti-inflammatory drugs (NSAIDS), antimalarials, corticosteroids, immunosuppressive drugs, and biological therapies. With the need to prevent side effects resulting from current treatments and acquire better clinical remission, developing a novel pharmaceutical treatment is extremely urgent. The concept of T cell vaccination (TCV) has been raised as the finding that immunization with attenuated autoreactive T cells is capable of inducing T cell-dependent inhibition of autoimmune responses. TCV may act as an approach to control unwanted adaptive immune response through eliminating the autoreactive T cells. Over the past decades, the effect of TCV has been justified in several animal models of autoimmune diseases including experimental autoimmune encephalomyelitis (EAE), murine autoimmune diabetes in nonobese diabetic (NOD) mice, collagen-induced arthritis (CIA), and so on. Meanwhile, clinical trials of TCV have confirmed the safety and efficacy in corresponding autoimmune diseases ranging from multiple sclerosis (MS) to systemic lupus erythematosus (SLE). This review aims to summarize the ongoing experimental and clinical trials and elucidate possible molecule mechanisms of TCV.

Pregnancy Associated with Systemic Lupus Erythematosus: Immune Tolerance in Pregnancy and Its Deficiency in Systemic Lupus Erythematosus--An Immunological Dilemma

Pregnancy is a physiological condition that requires immune tolerance to the product of conception. Systemic lupus erythematosus (SLE) is a disease with well-represented immune mechanisms that disturb immune tolerance. The association of pregnancy with systemic lupus erythematosus creates a particular immune environment in which the immune tolerance specific of pregnancy is required to coexist with alterations of the immune system caused by SLE. The main role is played by T regulatory (Treg) cells, which attempt to regulate and adapt the immune system of the mother to the new conditions of pregnancy. Other components of the immune system also participate to maintain maternal-fetal immune tolerance. If the immune system of pregnant women with SLE is not able to maintain maternal immune tolerance to the fetus, pregnancy complications (miscarriage, fetal hypotrophy, and preterm birth) or maternal complications (preeclampsia or activation of SLE, especially in conditions of lupus nephritis) may occur. In certain situations this can be responsible for neonatal lupus. At the same time, it must be noted that during pregnancy, the immune system is able to achieve immune tolerance while maintaining the anti-infectious immune capacity of the mother. Immunological monitoring of pregnancy during SLE, as well as of the mother's disease, is required. It is important to understand immune tolerance to grafts in transplant pathology.

Roles of γδ T cells in the pathogenesis of autoimmune diseases

γδ T cells are a minor population of T cells that express the TCR γδ chains, mainly distributed in the mucosal and epithelial tissue and accounting for less than 5% of the total T cells in the peripheral blood. By bridging innate and adaptive immunity, γδ T cells play important roles in the anti-infection, antitumor, and autoimmune responses. Previous research on γδ T cells was primarily concentrated on infectious diseases and tumors, whereas their functions in autoimmune diseases attracted much attention. In this paper, we summarized the various functions of γδ T cells in two prototypical autoimmune connective tissue diseases, that is, SLE and RA, elaborating on their antigen-presenting capacity, secretion of proinflammatory cytokines, immunomodulatory effects, and auxiliary function for B cells, which contribute to overproduction of proinflammatory cytokines and pathogenic autoantibodies, ultimately leading to the onset of these autoimmune diseases. Elucidation of the roles of γδ T cells in autoimmune diseases is not only conducive to in-depth understanding of the pathogenesis of these diseases, but also beneficial in providing theoretical support for the development of γδ T-cell-targeted therapy.

T cell-independent spontaneous loss of tolerance by anti-double-stranded DNA B cells in C57BL/6 mice

Systemic lupus erythematosus is characterized by loss of tolerance to DNA and other nuclear Ags. To understand the role of T cells in the breaking of tolerance, an anti-DNA site-specific transgenic model of spontaneous lupus, B6x56R, was studied. T cells were eliminated by crossing B6x56R with CD4(-/)(-) or TCRbeta(-/-)delta(-/-) mice, and the effects on anti-dsDNA serum levels, numbers of anti-dsDNA Ab-secreting cells, and isotypes of anti-dsDNA were analyzed. In addition, the development and activation of B cells in these mice were examined. Surprisingly, the presence of T cells made little difference in the development and character of the serum anti-dsDNA Ab in B6x56R mice. At 1 mo of age, anti-dsDNA Abs were somewhat lower in mice deficient in alphabeta and gammadelta T cells. Levels of Abs later were not affected by T cells, nor was autoantibody class switching. B cell activation was somewhat diminished in T cell-deficient mice. Thus, in the B6 background, the presence of an anti-dsDNA transgene led the production of autoantibodies with a specificity and isotype characteristic of murine systemic lupus erythematosus with little influence from T cells. TLR9 also did not appear to play a role. Although we do not yet understand the mechanism of this failure of immunoregulation, these results suggest that similar processes may influence autoimmunity associated with clinical disease.

Regulatory T cells and systemic lupus erythematosus

Regulatory T cells, especially CD4+CD25+ T cells, "natural killer" T cells and gammadelta T cells, are central in the maintenance of peripheral tolerance and the protection from the development of autoimmune diseases. Numerical or functional modifications of these cell populations were demonstrated to lead to the breakdown of tolerance and the emergence of autoimmunity. Involvement of regulatory T cells in the pathogenesis of systemic autoimmune diseases, such as systemic lupus erythematosus, might be of first importance. In murine models and patients with lupus, these regulatory T cells seem to be reduced in number. Functional deficiencies have also been described in a few studies. A better knowledge of regulatory T cell functional properties in systemic autoimmune diseases is essential to manipulate these cells and hopefully to restore immune tolerance.

The integration of conventional and unconventional T cells that characterizes cell-mediated responses

This review builds on evidence that cell-mediated immune responses to bacteria, viruses, parasites, and tumors are an integration of conventional and unconventional T-cell activities. Whereas conventional T cells provide clonal antigen-specific responses, unconventional T cells profoundly regulate conventional T cells, often suppressing their activities such that immunopathology is limited. By extrapolation, immunopathologies and inflammatory diseases may reflect defects in regulation by unconventional T cells. To explore the function of unconventional T cells, several extensive gene expression analyses have been undertaken. These studies are reviewed in some detail, with emphasis on the mechanisms by which unconventional T cells may exert their regulatory functions. Highlighting the fundamental nature of T-cell integration, we also review emerging data that the development of conventional and unconventional T cells is also highly integrated.

Contribution of alphabeta and gammadelta T cells to the generation of primary immunoglobulin G-driven autoimmune response in immunoglobulin- mu-deficient/lpr mice

Class switch recombination (CSR) is a T-cell-dependent mechanism regulating isotype switching in activated mature B cells. Recently we showed that T-cell-independent CSRs occur spontaneously during B lymphopoiesis, but such cells are negatively selected by Fas signalling. In immunoglobulin mu-deficient mice, lack of Fas rescues isotype-switched B cells, resulting in generation of an autoimmune primary immunoglobulin G (IgG) repertoire in muMT/lpr mice. In the present study, we studied the role of alphabeta and gammadelta T cells in regulating this primary gammaH-driven repertoire. We found that a lack of alphabeta T cells significantly inhibited IgG production and autoimmunity in muMT/lpr mice, whereas a lack of gammadelta T cells resulted in augmented IgG production and autoimmunity. Also, a lack of T cells in muMT mice rescued isotype-switched B cells and serum IgG, probably owing to the lack of available FasL. We suggest that although CSRs in B-cell lymphopoiesis are T-cell independent, alphabeta T cells are important in the expansion of isotype-switched B-cell precursors and in promoting gammaH-driven autoimmunity, whereas gammadelta T cells regulate these cells.

Susceptibility of T cell receptor-alpha chain knock-out mice to ultraviolet B light and fluorouracil: a novel model for drug-induced cutaneous lupus erythematosus

The anticancer agent 5-fluorouracil (FU) frequently induces cutaneous lupus erythematosus (LE) lesions on sun exposed sites. Based on this observation, we have tried to establish a cutaneous LE model of C57BL/6 J (B6) mice, B6 T cell receptor (TCR)-alpha(-/-) mice and B6 TCR-delta(-/-) mice treated with FU and/or ultraviolet B light (UVBL) in order to clarify the role of T cells and the cytokine profile of cutaneous lupus lesions. Cutaneous LE-like skin lesions could be induced in TCR-alpha(-/-) mice with low FU (0.2 mg) plus UVBL, and in B6 mice treated with a high dose of FU (2.0 mg) plus UVBL. In contrast, low FU plus UVBL induced such skin lesions in TCR-delta(-/-) mice at a very low incidence. Specifically, the skin lesions of TCR-alpha(-/-) mice with low FU plus UVBL appeared more rapidly and were more severe than lesions in B6 mice. The former had the common characteristic features of human chronic cutaneous LE such as typical histology, positive IgG at the dermoepidermal junction, low antinuclear antibody and low mortality. Furthermore, a Th1 response was induced in the development of drug-induced cutaneous LE. FU and UVBL-induced cutaneous LE-like eruption is an excellent model for better understanding the pathomechanisms of skin lesion development in LE.

gammadelta T-cell clones from intestinal intraepithelial lymphocytes inhibit development of CTL responses ex vivo

Oral administration of antigen induces a state of tolerance that is associated with activation of CD8+ T cells that can transfer unresponsiveness to naïve syngeneic hosts. These T cells are not lytic, but they inhibit development of antibody, CD4+ T helper cell, and CD8+ cytotoxic T lymphocyte (CTL) responses upon adoptive transfer into naïve, syngeneic mice. In addition, we have shown that depletion of gammadelta T cells by injection of the anti-delta chain antibody (GL3) down modulates the expression of gammadelta T-cell receptor (TCR) and inhibits the induction of oral tolerance to ovalbumin. Oral administration of antigen also fails to induce tolerance in TCR delta-chain knockout mice suggesting that gammadelta T cells play a critical, active role in tolerance induced by orally administered antigen. To further study the contribution of gammadelta T cells to tolerance, murine gammadelta T cells were isolated from intraepithelial lymphocytes (IEL) of the small intestine by stimulation with splenic filler cells, concanavalin A and growth factors. gammadelta IEL lines demonstrated lytic activity in a redirected lysis assay. gammadelta T-cell clones express different gammadelta TCR genes and secrete large amounts of interleukin (IL)-10, but little or no IL-2, IL-4, or interferon-gamma. gammadelta IEL clones expressed transforming growth factor-beta1 and macrophage migration inhibitory factor, as well as IL-10, mRNA. Moreover, gammadelta T-cell clones potently inhibited the generation of CTL responses by secreted molecules rather than by direct cell-to-cell contact.

T-cell effector mechanisms: gammadelta and CD1d-restricted subsets

Gammadelta T lymphocytes and CD1d-restricted natural killer T cells are classified as innate T lymphocytes, which perform effector functions that protect from malignancy and maintain tissue integrity. Innate T cells also play important regulatory roles in autoimmunity, inflammation and infection. Recent advances have established innate T cells as both effectors and regulators of disease in biological models.