Skin and gut imprinted helper T cell subsets exhibit distinct functional phenotypes in central nervous system autoimmunity

Multidimensional single-cell analyses of T cells have fueled the debate about whether there is extensive plasticity or 'mixed' priming of helper T cell subsets in vivo. Here, we developed an experimental framework to probe the idea that the site of priming in the systemic immune compartment is a determinant of helper T cell-induced immunopathology in remote organs. By site-specific in vivo labeling of antigen-specific T cells in inguinal (i) or gut draining mesenteric (m) lymph nodes, we show that i-T cells and m-T cells isolated from the inflamed central nervous system (CNS) in a model of multiple sclerosis (MS) are distinct. i-T cells were Cxcr6+, and m-T cells expressed P2rx7. Notably, m-T cells infiltrated white matter, while i-T cells were also recruited to gray matter. Therefore, we propose that the definition of helper T cell subsets by their site of priming may guide an advanced understanding of helper T cell biology in health and disease.

Murine T-Cell Transfer Colitis as a Model for Inflammatory Bowel Disease

Inflammatory bowel disease (IBD) is a group of severe chronic inflammatory conditions of the human gastrointestinal tract. Murine models of colitis have been invaluable tools to improve the understanding of IBD development and pathogenesis. While the disease etiology of IBD is complex and multifactorial, CD4+ T helper cells have been shown to strongly contribute to the disease pathogenesis of IBD. Here, we present a detailed protocol of the preclinical model of T-cell transfer colitis, which can easily be utilized in the laboratory to study T helper cell functions in intestinal inflammation.

The Anticancer Potential of T Cell Receptor-Engineered T Cells

Adoptively transferred T cell receptor (TCR)-transgenic T cells (TCR-T cells) are not restricted by cell surface expression of their targets and are therefore poised to become a main pillar of cellular cancer immunotherapies. Addressing clinical and laboratory data, we discuss emerging features for the efficient deployment of novel TCR-T therapies, such as selection of ideal TCRs targeting validated epitopes with well-characterized cancer cell expression and processing, enhancing TCR-T effector function, trafficking, expansion, persistence, and memory formation by strategic selection of substrate cells, and gene-engineering with synthetic co-stimulatory circuits. Overall, a better understanding of the relevant mechanisms of action and resistance will help prioritize the vast array of potential TCR-T optimizations for future clinical products.

Proteome analysis revealed the essential functions of protein phosphatase PP2A in the induction of Th9 cells

Proteomic analysis identifies post-translational functions of proteins, which remains obscure in transcriptomics. Given the important functions of Th9 cells in anti-tumor immunity, we performed proteome analysis of Th9 cells to understand the involvement of proteins that might be crucial for the anti-tumor functions of Th9 cells. Here we performed a comprehensive proteomic analysis of murine Th0 and Th9 cells, and identified proteins that are enriched in Th9 cells. Pathway analysis identified an abundance of phosphoproteins in the proteome of Th9 cells as compared to Th0 cells. Among upregulated phosphoproteins, Ppp2ca (catalytic subunit of protein phosphatase, PP2A) was found to be highly enriched in Th9 cells. Although the role of PP2A has been shown to regulate the differentiation and functions of Th1, Th2, Th17 and Tregs, its role in the differentiation and functions of Th9 cells is not identified yet. Here we found that PP2A is required for the induction of Th9 cells, as PP2A inhibition leads to the suppression of IL-9 and expression of key transcription factors of Th9 cells. PP2A inhibition abrogates Th9 cell-mediated anti-tumor immune response in B16-OVA melanoma tumor model. Thus, we report that PP2A is essential for the differentiation and anti-tumor functions of Th9 cells.

Vaccines targeting helper T cells for cancer immunotherapy

There are compelling arguments for designing cancer vaccines specifically to induce CD4+ helper T cell responses. Recent studies highlight the crucial role of proliferating, activated effector memory Th1 CD4+ T cells in effective antitumor immunity and reveal that CD4+ T cells induce more durable immune-mediated tumor control than CD8+ T cells. CD4+ T cells promote antitumor immunity by numerous mechanisms including enhancing antigen presentation, co-stimulation, T cell homing, T cell activation, and effector function. These effects are mediated at sites of T cell priming and at the tumor microenvironment. Several cancer vaccine approaches induce durable CD4+ T cell responses and have promising clinical activity. Future work should further optimize vaccine adjuvants and combination therapies incorporating helper peptide vaccines.

Helper function of CD4⁺ lymphocytes in antiviral immunity in ginbuna crucian carp, Carassius auratus langsdorfii

Although many recent studies have suggested that CD4(+) helper T cell (Th-cell) functions are well conserved among teleost fishes and mammals, there is little evidence that CD4(+) Th-cells in fish are actually involved in both humoral and cell-mediated immunity during a secondary immune response. In the present study, adoptive transfer using clonal ginbuna crucian carp and crucian carp hematopoietic necrosis virus (CHNV) was used to investigate the functions of CD4(+) cells during humoral and cell-mediated immunity. With regard to humoral immunity, transplanting CHNV-sensitized donor cells, containing CD4(+) cells, into naive fish induced more rapid and stronger antibody production than by transplanting non-sensitized donor cells or sensitized donor cells lacking CD4(+) cells. During cell-mediated immunity, no significant differences were found in recipients that received sensitized cells regardless of whether the donor cells contained CD4(+) cells, although recipients that received both sensitized donor cells (with and without CD4(+) cells) exhibited more efficient cell-mediated cytotoxicity than those that received non-sensitized donor cells. These findings suggest that inducing a secondary antibody response requires CD4(+) cell help, and secondary cell-mediated immunity can be induced both by CD4(+) cells and leukocytes other than CD4(+) cells.

Transcription factor IRF4 determines germinal center formation through follicular T-helper cell differentiation

Follicular T-helper (T(FH)) cells cooperate with GL7(+)CD95(+) germinal center (GC) B cells to induce antibody maturation. Herein, we identify the transcription factor IRF4 as a T-cell intrinsic precondition for T(FH) cell differentiation and GC formation. After immunization with protein or infection with the protozoon Leishmania major, draining lymph nodes (LNs) of IFN-regulatory factor-4 (Irf4(-/-)) mice lacked GCs and GC B cells despite developing normal initial hyperplasia. GCs were also absent in Peyer's patches of naive Irf4(-/-) mice. Accordingly, CD4(+) T cells within the LNs and Peyer's patches failed to express the T(FH) key transcription factor B-cell lymphoma-6 and other T(FH)-related molecules. During chronic leishmaniasis, the draining Irf4(-/-) LNs disappeared because of massive cell death. Adoptive transfer of WT CD4(+) T cells or few L. major primed WT T(FH) cells reconstituted GC formation, GC B-cell differentiation, and LN cell survival. In support of a T-cell intrinsic IRF4 activity, Irf4(-/-) T(FH) cell differentiation was not rescued by close neighborhood to transferred WT T(FH) cells. Together with its known B lineage-specific roles during plasma cell maturation and class switch, our study places IRF4 in the center of antibody production toward T-cell-dependent antigens.

Inhibition of Th17 cells regulates autoimmune diabetes in NOD mice

OBJECTIVE

The T helper 17 (Th17) population, a subset of CD4-positive T-cells that secrete interleukin (IL)-17, has been implicated in autoimmune diseases, including multiple sclerosis and lupus. Therapeutic agents that target the Th17 effector molecule IL-17 or directly inhibit the Th17 population (IL-25) have shown promise in animal models of autoimmunity. The role of Th17 cells in type 1 diabetes has been less clear. The effect of neutralizing anti-IL-17 and recombinant IL-25 on the development of diabetes in NOD mice, a model of spontaneous autoimmune diabetes, was investigated in this study.

RESEARCH DESIGN AND METHODS AND RESULTS

Although treatment with either anti-IL-17 or IL-25 had no effect on diabetes development in young (<5 weeks) NOD mice, either intervention prevented diabetes when treatment was started at 10 weeks of age (P < 0.001). Insulitis scoring and immunofluorescence staining revealed that both anti-IL-17 and IL-25 significantly reduced peri-islet T-cell infiltrates. Both treatments also decreased GAD65 autoantibody levels. Analysis of pancreatic lymph nodes revealed that both treatments increased the frequency of regulatory T-cells. Further investigation demonstrated that IL-25 therapy was superior to anti-IL-17 during mature diabetes because it promoted a period of remission from new-onset diabetes in 90% of treated animals. Similarly, IL-25 delayed recurrent autoimmunity after syngeneic islet transplantation, whereas anti-IL-17 was of no benefit. GAD65-specific ELISpot and CD4-positive adoptive transfer studies showed that IL-25 treatment resulted in a T-cell-mediated dominant protective effect against autoimmunity.

CONCLUSIONS

These studies suggest that Th17 cells are involved in the pathogenesis of autoimmune diabetes. Further development of Th17-targeted therapeutic agents may be of benefit in this disease.

Cutting edge: in vitro generated Th17 cells maintain their cytokine expression program in normal but not lymphopenic hosts

Upon activation, naive CD4(+) T cells differentiate into effector Th cell subsets. The stability and plasticity of effector Th cells have not been well understood. In this study we used an IL-17F-red fluorescent protein reporter mouse to analyze the plasticity of Th17 cells in vitro and in vivo. We found that in vitro generated Th17 cells poorly maintained their differentiation program in vitro and could be reprogrammed into other T cell lineages. Moreover, upon transfer into lymphopenic hosts, Th17 cells rapidly lost their IL-17 expression and were converted into Th1 cells independently of IL-7 signaling. However, Th17 cells maintained their phenotypes well in normal animals, even in the absence of Ag and inflammation. These results, although suggesting the plasticity of Th17 cells, also indicate active maintenance of their program in vivo.

Th17-polarized immune response in a murine model of hypersensitivity pneumonitis and lung fibrosis

Hypersensitivity pneumonitis is an environmental lung disease characterized by a diffuse mononuclear cell infiltrate in the lung that can progress to pulmonary fibrosis with chronic exposure to an inhaled Ag. Using a well-established murine model of hypersensitivity pneumonitis, we repeatedly exposed C57BL/6 mice to Saccharopolyspora rectivirgula to investigate whether T cells are required for lung fibrosis. In the absence of alphabeta T cells, TCRbeta(-/-) mice exposed to S. rectivirgula for 4 wk had markedly decreased mononuclear infiltrates and collagen deposition in the lung compared with wild-type C57BL/6 mice. In contrast to CD8(+) T cells, adoptive transfer of CD4(+) T cells reconstituted the S. rectivirgula-induced inflammatory and fibrotic response, suggesting that the CD4(+) T cell represents the critical alphabeta T cell subset. Cytokine analysis of lung homogenates at various time points after S. rectivirgula exposure failed to identify a predominant Th1 or Th2 phenotype. Conversely, IL-17 was found in the lung at increasing concentrations with continued exposure to S. rectivirgula. Intracellular cytokine staining revealed that 14% of CD4(+) T cells from the lung of mice treated with S. rectivirgula expressed IL-17A. In the absence of IL-17 receptor signaling, Il17ra(-/-) mice had significantly decreased lung inflammation and fibrosis compared with wild-type C57BL/6 mice. These data are the first to demonstrate an important role for Th17-polarized CD4(+) T lymphocytes in the immune response directed against S. rectivirgula in this murine model of hypersensitivity pneumonitis and pulmonary fibrosis.

Lack of effective MUC1 tumor antigen-specific immunity in MUC1-transgenic mice results from a Th/T regulatory cell imbalance that can be corrected by adoptive transfer of wild-type Th cells

Glycoprotein tumor Ag MUC1 is overexpressed on the majority of epithelial adenocarcinomas. CTLs that recognize MUC1 and can kill tumor cells that express this molecule have been found in cancer patients, yet they are present in low frequency and unable to eradicate MUC1(+) tumors. Patients also make anti-MUC1 Abs but predominantly of the IgM isotype reflecting the lack of effective MUC1-specific Th responses. Mice transgenic for the human MUC1 gene (MUC1-Tg) are similarly hyporesponsive to MUC1. We used a vaccine consisting of dendritic cells loaded with a long synthetic MUC1 peptide to investigate the fate and function of MUC1-specific CD4(+) Th elicited in wild-type (WT) or MUC1-Tg mice or adoptively transferred from vaccinated WT mice. We show that hyporesponsiveness of MUC1-Tg mice to this vaccine is a result of insufficient expansion of Th cells, while at the same time their regulatory T cells are efficiently expanded to the same extent as in WT mice and exert a profound suppression on MUC1-specific B and T cell responses in vivo. Adoptive transfer of WT Th cells relieved this suppression and enhanced T and B cell responses to subsequent MUC1 immunization. Our data suggest that the balance between Th and regulatory T cells is a critical parameter that could be modulated to improve the response to cancer vaccines.

The role of BLyS/BLyS receptors in anti-chromatin B cell regulation

B lymphocyte stimulator (BLyS), also known as B cell-activating factor, is a key positive regulator of B cell homeostasis, and elevated levels of BLyS have been observed in systemic lupus erythematosus (SLE) patients. Given that anti-chromatin auto-antibodies are one of the hallmarks of SLE, we examined the role of BLyS and its receptors in the regulation of anti-chromatin B cells. We demonstrate that exogenous BLyS treatment leads to an increase in B cell numbers, particularly anti-chromatin B cells; yet, their localization in the spleen and auto-antibody production remain unaffected. We also examined transmembrane activator and CAML interactor (TACI), BLyS receptor 3 (BR3) and B cell maturation antigen expression on anti-chromatin B cells before and after receiving T cell help. Interestingly, in the absence of T cell help, TACI expression is greater on immature anti-chromatin B cells compared with immature Tg(-) B cells, whereas BR3 levels are comparable. After receiving T cell help, the anti-chromatin B cells that have differentiated into short-lived plasma cells no longer express BR3 but retain TACI. These data suggest a novel role for TACI in anti-chromatin B cell homeostasis and differentiation.

Dendritic Cell-Independent B Cell Activation During Acute Virus Infection: A Role for Early CCR7-Driven B-T Helper Cell Collaboration

This study provides a detailed spatiotemporal interaction analysis between B cells, Th cells, and dendritic cells (DC) during the generation of protective antiviral B cell immunity. Following vesicular stomatitis virus (VSV) infection, conditional ablation of CD11c-positive DC at the time-point of infection did not impair extrafollicular plasma cell generation and Ig class switching. In contrast, the generation of Th and B cell responses following immunization with recombinant VSV-glycoprotein was DC-dependent. Furthermore, we show that the CCR7-dependent interplay of the three cell-types is crucial for virus-neutralizing B cell responses in the presence of limiting amounts of Ag. An immediate event following VSV infection was the CCR7-mediated interaction of VSV-specific B and Th cells at the T cell-B cell zone border that facilitated plasma cell differentiation and Th cell activation. Taken together, these experiments provide evidence for a direct, CCR7-orchestrated and largely DC-independent mutual activation of Th cells and Ag-specific B cells that is most likely a critical step during early immune responses against cytopathic viruses.

Systemic autoimmune disease caused by autoreactive B cells that receive chronic help from Ig V region-specific T cells

B cells present BCR V region-derived Id-peptides on their MHC class II molecules to Id-specific CD4+ T cells. Prolonged Id-driven T-B collaboration could cause autoimmune disease, but this possibility is difficult to test in normal individuals. We have investigated whether mice doubly transgenic for an Id+ Ig L chain and an Id-specific TCR develop autoimmune disease. Surprisingly, T cell tolerance was not complete in these mice because a low frequency of weakly Id-reactive CD4+ T cells accumulated with age. These escapee Id-specific T cells provided chronic help for Id+ B cells, resulting in a lethal systemic autoimmune disease including germinal center reactions, hypergammaglobulinemia, IgG autoantibodies, glomerulonephritis, arthritis, skin affection, and inflammatory bowel disease. Inflamed tissues contained foci of Id-driven T-B collaboration, with deposition of IgG and complement. The disease could be transferred with B and T cells. The results demonstrate a novel mechanism for development of autoimmune disease in which self-reactive Id+ B cells receive prolonged help from Id-specific T cells, thus bypassing the need for help from T cells recognizing conventional Ag.

Intravenous Injection of a D1 Protein of the Smith Proteins Postpones Murine Lupus and Induces Type 1 Regulatory T Cells

T cells that recognize nucleoproteins are required for the production of anti-dsDNA Abs involved in lupus development. SmD1 83-119 (a D1 protein of the Smith (Sm) proteins, part of small nuclear ribonucleoprotein) was recently shown to provide T cell help to anti-dsDNA Abs in the NZB/NZW model of lupus. Using this model in the present study, we showed that high dose tolerance to SmD1 (600-1000 microg i.v. of SmD1(83-119) peptide/mo) delays the production of autoantibodies, postpones the onset of lupus nephritis as confirmed by histology, and prolongs survival. Tolerance to SmD1 83-119 was adoptively transferred by CD90+ T cells, which also reduce T cell help for autoreactive B cells in vitro. One week after SmD1 83-119 tolerance induction in prenephritic mice, we detected cytokine changes in cultures of CD90+ T and B220+ B cells with decreased IFN-gamma and IL-4 expression and an increase in TGFbeta. Increased frequencies of regulatory IFN-gamma+ and IL10+ CD4+ T cells were later detected. Such regulatory IL-10+/IFN-gamma+ type 1 regulatory T cells prevented autoantibody generation and anti-CD3-induced proliferation of naive T cells. In conclusion, these results indicate that SmD1 83-119 peptide may play a dominant role in the activation of helper and regulatory T cells that influence autoantibody generation and murine lupus.

Is there a place for immunomodulation in assisted reproduction techniques?

We briefly review the history of the concepts of the materno foetal relationship, and the (various) rationales which have been used to justify lymphocyte alloimmunisation (LA) as a treatment for recurrent spontaneous abortion of putative immune origins. The effectiveness of the treatment is at best dubious and limited to a small number of women for which there is no real positive selection rationale, at worst it is not efficient. The rationales themselves are rather "evolutive". The present one is to use the Th1:Th2 paradigm and, thus, to propose to "dampen NK activity" in abortion prone women and this concept has been extended by some to implantation failure. We briefly review why the Th1:Th2 paradigms is no longer fully valid, describe briefly why it is inappropriate for implantation, and conclude that alloimmunisation should no longer be proposed for RSA, hence, more for implantation failure. We, however, do not reject immunotherapy, but we believe that molecular and cellular defects specific approaches should be used, tailored for the specific pathway whose disruption cause the clinical symptom.

4-1BB-dependent inhibition of immunosuppression by activated CD4+CD25+ T cells

4-1BB (CD137) is a costimulatory molecule involved in the activation and survival of CD4, CD8, and natural killer cells. Although a great deal has been learned as to how 4-1BB-mediated signaling governs the immunity of conventional T cells, the functional role of 4-1BB in the context of CD4(+)CD25(+) regulatory T cell (Tr) activation is largely unknown. Using 4-1BB-intact and -deficient mice, we investigated the effect of the 4-1BB/4-1BB ligand pathway on the suppressive function of Tr cells. Our data indicate that although 4-1BB is expressed on Tr cells, its contribution to their proliferation is minimal. We also showed that signaling through the 4-1BB receptor inhibited the suppressive function of Tr cells in vitro and in vivo. It is interesting that anti-4-1BB-mediated but not anti-GITR-directed inhibition was more potent when Tr cells were preactivated. Collectively, these data indicate that 4-1BB signaling is critical in Tr cell immunity.

Helper CD4+ T cells for IgE response to a dietary antigen develop in the liver

BACKGROUND

Although T-cell responses to food antigens are normally inhibited either by deletion, active suppression, or both of antigen-specific T cells, T helper cells for IgE response to a food antigen still develop by unknown mechanisms in a genetically susceptible host.

OBJECTIVE

We determined the site at which those IgE helper T cells develop.

METHODS

We administered ovalbumin (OVA) orally to DO11.10 mice and studied CD4+ T cells in Peyer's patches, the spleen, and the liver. Helper activity for IgE response was assessed by adoptively transferring those CD4+ T cells to naive BALB/c mice, followed by systemic immunization with OVA.

RESULTS

OVA-specific CD4+ T cells were deleted by cell death in the liver and Peyer's patches of DO11.10 mice fed OVA. OVA-specific CD4+ T cells that survived apoptosis in the liver expressed Fas ligand and secreted IL-4, IL-10, and transforming growth factor beta(1). CD4+ T cells producing IFN-gamma were deleted in the liver by repeated feeding of OVA. On transfer of CD4+ T cells to naive mice and systemic immunization with OVA, a marked increase in OVA-specific IgE response developed only in the mice that received hepatic CD4+ T cells from OVA-fed mice, the effect of which was not observed in the recipients of hepatic CD4+ T cells deficient in IL-4. In addition, significant suppression of delayed-type hypersensitivity and IgG(1)/IgG(2a) responses to OVA was observed in the recipients of hepatic CD4+ T cells, and this suppression required Fas/Fas ligand interaction.

CONCLUSION

Together, these results suggested that a food antigen might negatively select helper T cells for IgE response to the antigen by preferential deletion of T(H)1 cells in the liver.

T-helper 1 cells induce alveolitis but do not lead to pulmonary fibrosis in mice

T-helper (Th)1 cells have a pivotal role in the pathogenesis of hypersensitivity pneumonitis. Continued low-level exposure to the antigens may induce chronic hypersensitivity pneumonitis with lung fibrosis. Although such exposure may activate Th1 cells in the lung, it is not known whether activation of Th1 cells per se can lead to pulmonary fibrosis. To determine this, the lung pathology induced by Th1 clones was investigated. Mice (BALB/c) were injected intraperitoneally with Th1 clones 1-4 times. Each injection was performed 4 days apart and was followed by repeated exposure to aerosolised ovalbumin (OVA) once a day for 5 days. The number of macrophages and lymphocytes in bronchoalveolar lavage fluids (BALF) increased as the number of Th1 transfers increased. The number of neutrophils also increased but peaked in the second transfer and then decreased following further transfers. Increased cell infiltration, thickness of alveolar walls and number of type II cells in the lung occurred. However, histological findings showed no evidence of fibrosis and hydroxyproline levels did not increase. Findings of histology and BALF were ameliorated 2 weeks after the discontinuation of OVA exposure, indicating the reversibility of the Th1-induced pathology. In conclusion, adoptive transfer of T-helper 1 cells results in reversible alveolitis but does not lead to pulmonary fibrosis.

Enhancement of MHC class II-restricted responses by receptor-mediated uptake of peptide antigens

Peptides, either as altered peptide ligands, competitors, or vaccines, offer an outstanding potential for regulating immune responses because of their exquisite specificity. However, a major problem associated with peptide therapies is that they are poorly taken up by APCs. Because of poor bioavailability, high concentrations and repeated treatments are required for peptide therapies in vivo. To circumvent this problem, we tested whether covalently coupling a peptide T cell determinant, OVA(323-339), to transferrin (Tf) enhances APC uptake and presentation as monitored by Th cell activation. Functional analysis of the Tf-peptide conjugates revealed that the conjugates were presented 10,000- and 100-fold more effectively by B cells than intact Ag and free peptide, respectively. Furthermore, we demonstrate that the Tf-peptide conjugates are taken up by B cells through a receptor-mediated process and subsequently delivered to the lysosomal compartment. Using an adoptive transfer assay, we show that that the Tf-peptide complexes are 100-fold more effective in vivo than the free peptide in activating CD4(+) T cells by following an early activation marker, CD69. Our results demonstrate that coupling peptides to Tf enhances peptide presentation, thereby making it possible to take full advantage of peptide-specific therapies in modulating T cell responses.

CD4 T-helper cells engineered to produce IL-10 prevent allergen-induced airway hyperreactivity and inflammation

BACKGROUND

T(H)2 cells play a critical role in the pathogenesis of asthma, but the precise immunologic mechanisms that inhibit T(H)2 cell function in vivo are not well understood.

OBJECTIVE

The purpose of our studies was to determine whether T cells producing IL-10 regulate the development of asthma.

METHODS

We used gene therapy to generate ovalbumin-specific CD4 T-helper cells to express IL-10, and we examined their capacity to regulate allergen-induced airway hyperreactivity.

RESULTS

We demonstrated that the CD4 T-helper cells engineered to express IL-10 abolished airway hyperreactivity and airway eosinophilia in BALB/c mice sensitized and challenged with ovalbumin and in SCID mice reconstituted with ovalbumin-specific T(H)2 effector cells. The inhibitory effect of the IL-10-secreting T-helper cells was accompanied by the presence of increased quantities of IL-10 in the bronchoalveolar lavage fluid, was antigen-specific, and was reversed by neutralization of IL-10. Moreover, neutralization of IL-10 by administration of anti-IL-10 mAb in mice sensitized and challenged with ovalbumin seriously exacerbated airway hyperreactivity and airway inflammation.

CONCLUSION

Our results demonstrate that T cells secreting IL-10 in the respiratory mucosa can indeed regulate T(H)2-induced airway hyperreactivity and inflammation, and they strongly suggest that IL-10 plays an important inhibitory role in allergic asthma.

Orally tolerized T cells are only able to enter B cell follicles following challenge with antigen in adjuvant, but they remain unable to provide B cell help

Although it is well documented that feeding Ag can tolerize or prime systemic humoral and cell-mediated immune responses, the mechanisms involved remain unclear. Elucidation of these mechanisms remains, in part, complicated by the inability to assess responses by individual lymphocyte populations. In the past, in vivo studies have examined T cell responses at the gross level by examining their ability to support B cell Ab production. However, as the fed Ag has the capacity to affect B cells directly, analyzing the functional capacity of a single Ag-specific T cell population in vivo has been difficult. Using a double-adoptive transfer system, we have primed or tolerized T cells, independently of B cells with a high dose of fed Ag, and examined the ability of these primed or tolerized T cells to support B cell clonal expansion in response to a conjugated Ag in vivo. We have been able to show that primed T cells support B cell clonal expansion and Ab production whereas tolerized T cells do not. Thus, we have provided direct evidence that tolerized T cells are functionally unable to help B cells in vivo. Furthermore, we have shown that this inability of tolerized T cells to support fulminant B cell responses is not a result of defective clonal expansion or follicular migration, since following challenge tolerized T cells are similar to primed T cells in both of these functions.

Immune elimination of Leishmania major in mice: implications for immune memory, vaccination, and reactivation disease

Infection of susceptible BALB/c mice with a large, moderate, or low number of Leishmania major parasites respectively results in progressive disease, the formation of substantial but stable lesions, denoted as borderline disease, and the absence of a visible lesion. Infection with a low number of parasites results over the long term in either subclinical infections or an asymptomatic state. Subclinical mice produce a predominant Th1 response and are resistant to challenge, in contrast to their asymptomatic counterparts. Statistical and other evidence suggest that the asymptomatic state can arise from a subclinical state following parasite clearance, with consequent loss of resistance. Cell transfer studies demonstrate unequivocally that immune cells from subclinical mice can protect naive mice against a pathogenic challenge and can clear the parasite, leaving the mice susceptible to a rechallenge infection. This susceptibility is associated with the disappearance of both parasite-specific effector and memory T cells from secondary lymphoid organs. These findings have implications for vaccination, maintenance of memory, and prevention of reactivation disease.

CD40 ligand promotes priming of fully potent antitumor CD4(+) T cells in draining lymph nodes in the presence of apoptotic tumor cells

The presence or absence of CD4(+) T cell help can determine the direction of adaptive immune responses toward either cross-priming or cross-tolerance. It has been demonstrated that interactions of CD40-CD40 ligand can replace CD4(+) T cell help and enable dendritic cells to prime cytotoxic T cells. Here, we demonstrate that antitumor reactivity induced in regional lymph nodes (LNs) by s.c. injection of CD40 ligand (CD40L)-transduced tumor (MCA205 CD40L) showed far superior therapeutic efficacy against established brain tumors of a weakly immunogenic fibrosarcoma, MCA205, when adoptively transferred. Coinjection of apoptotic, but not necrotic parental tumor cells with CD40L-expressing tumor cells caused a strong synergistic induction of antitumor reactivity in tumor-draining LNs. Freshly isolated T cells from LNs immunized with apoptotic parental tumor cells and MCA205 CD40L were capable of mediating regression of the parental tumor in vivo. In contrast, T cells derived from LNs immunized without MCA205 CD40L required ex vivo anti-CD3/IL-2 activation to elicit therapeutic activity. On anti-CD3/IL-2 activation, cells from LNs immunized with MCA205 CD40L exhibited superior per cell antitumor reactivity. An in vitro depletion study revealed that either CD4(+) or CD8(+) T cells could mediate therapeutic efficacy but that the antitumor efficacy mediated by CD4(+) T cells was far superior. Cytosolic flow cytometric analyses indicated that priming of CD4(+) cells in LNs draining CD40L-expressing tumors was polarized to the Th1 type. This is the first report that fully potent antitumor CD4(+) T cell priming was promoted by s.c. injection of CD40L-transduced tumor in the presence of apoptotic tumor cells.

Apoptotic deletion of Th cells specific for the 19-kDa carboxyl-terminal fragment of merozoite surface protein 1 during malaria infection

Immunity induced by the 19-kDa fragment of merozoite surface protein 1 is dependent on CD4+ Th cells. However, we found that adoptively transferred CFSE-labeled Th cells specific for an epitope on Plasmodium yoelii 19-kDa fragment of merozoite surface protein 1 (peptide (p)24), but not OVA-specific T cells, were deleted as a result of P. yoelii infection. As a result of infection, spleen cells recovered from infected p24-specific T cell-transfused mice demonstrated reduced response to specific Ag. A higher percentage of CFSE-labeled p24-specific T cells stained positive with annexin and anti-active caspase-3 in infected compared with uninfected mice, suggesting that apoptosis contributed to deletion of p24-specific T cells during infection. Apoptosis correlated with increased percentages of p24-specific T cells that stained positive for Fas from infected mice, suggesting that P. yoelii-induced apoptosis is, at least in part, mediated by Fas. However, bystander cells of other specificities also showed increased Fas expression during infection, suggesting that Fas expression alone is not sufficient for apoptosis. These data have implications for the development of immunity in the face of endemic parasite exposure.

Cognate T cell help is sufficient to trigger anti-nuclear autoantibodies in naive mice

The mechanisms involved in the initiation of anti-nuclear autoantibodies are unknown. In this study, we show that one factor allowing anti-nuclear autoantibodies to develop is the incomplete nature of immune tolerance to many of these proteins. Immune responses in mice toward the ubiquitous nuclear autoantigen La/SS-B are much weaker than responses to the xenoantigen, human La (hLa; 74% identical). However, in transgenic (Tg) mice expressing hLa, the Ab response to this neo-autoantigen was reduced to a level resembling the weak autoimmune response to mouse LA: Partial tolerance to endogenous La autoantigen was restricted to the T compartment because transfer of CD4(+) T cells specific for one or more hLa determinants into mice bearing the hLa transgene was sufficient to elicit production of anti-hLa autoantibodies. Notably, only hLa- specific T cells from non-Tg mice, and not T cells from hLa Tg mice, induced autoantibody production in hLa Tg mice. These findings confirm partial Th tolerance to endogenous La and indicate the existence in normal animals of autoreactive B cells continuously presenting La nuclear AG: Therefore, the B cell compartment is constitutively set to respond to particular nuclear autoantigens, implicating limiting Th responses as a critical checkpoint in the development of anti-nuclear autoantibodies in normal individuals.

In-vivo impaired T helper 1 cell development in submandibular lymph nodes due to IL-12 deficiency following antigen injection into the anterior chamber of the eye

PURPOSE

To determine the functional properties of antigen-specific T cells that accumulate in lymph nodes following injection of antigen into the anterior chamber (AC).

METHODS

Ovalbumin (OVA)-specific, CD4(+) transgenic T cell receptor (Tcr) T cells (KJ-126(+)) from DO11.10 mice were adoptively transferred into unirradiated syngeneic BALB/c mice who then received an injection of OVA in the AC or subcutaneously (SC). Three days later, KJ126(+) T cells in draining and non-draining lymph nodes were analyzed for clonal expansion, activation, and cell-cycle status by flow cytometry. In addition, the cells' functional phenotype was assessed in vitro by proliferation assays and cytokine production by ELISA.

RESULTS

Tcr T cells localized exclusively to draining lymph nodes after injection of OVA into the AC (neck) and SC (neck, axilla, brachial). In both cases, the KJ126(+) T cells displayed evidence of in-vivo activation and proliferation. T cells from AC-injected donors when stimulated in vitro with OVA produced small amounts of IL-2, but no IFN-gamma, IL-4, IL-5, IL-10, or TGFbeta. By contrast, T cells from SC-injected animals displayed a Th1-like phenotype (IL-2, IFN-gamma). The draining lymph nodes of mice that received systemic or intraocular administration of exogenous IL-12 at the time of the AC injection of OVA also contained KJ126(+) T cells that secreted IFN-gamma and IL-2.

CONCLUSION

Antigen attracts antigen-specific T cells to lymph nodes that drain the injection site. Whereas responding T cells in nodes draining SC-injection sites differentiated into Th1-like cells, T cells in nodes draining AC injection failed to differentiated beyond the capacity to secrete IL-2 in response to antigen. Since the failure was reversed by exogenous IL-12, we propose that orderly differentiation of antigen-specific T cells down the Th1 pathway is aborted by the eye, because of a deficit in IL-12 production.

Tumor necrosis factor inhibitor ameliorates murine intestinal graft-versus-host disease

BACKGROUND & AIMS

Transfer of T helper cells from DBA/2 mice to irradiated allogeneic B6D2F1 mice leads to development of colonic graft-versus-host disease with pathological features of inflammatory bowel disease. To examine the role of tumor necrosis factor (TNF) in graft-versus-host disease enteropathy, an adenoviral vector encoding a TNF inhibitor protein was administered.

METHODS

Irradiated B6D2F1 mice were infused with DBA/2 bone marrow and spleen cells. Mice then received either a control beta-galactosidase-encoding adenovirus or an adenovirus encoding a TNF inhibitor, composed of the extracellular domain of the human 55-kilodalton TNF receptor linked to the murine immunoglobulin G1 heavy chain. Mucosal permeability to sucralose and colonic histology were assessed 14 and 25 days after transplantation.

RESULTS

Less diarrhea was observed in DBA/2 --> B6D2F1 mice expressing the TNF inhibitor, and colonic sections from these mice had significantly less inflammation and epithelial cell abnormalities. In TNF inhibitor recipients, mucosal permeability to sucralose was similar to that in nonirradiated control mice and significantly less than in recipients of the control adenovirus.

CONCLUSIONS

TNF inhibition decreases the severity of enteropathy in the DBA/2 --> B6D2F1 murine model of colonic graft-versus-host disease.

Abnormalities of B cells and dendritic cells in SAMP1 mice

The age-related changes in the function of antigen-presenting cells (APC) were examined using a substrain of senescence-accelerated mouse (SAMP1). In the primary mixed lymphocyte reaction (MLR), dendritic cells (DC) from aged SAMP1 mice showed less stimulatory activity than those of age-matched BALB/c or young SAMP1 mice. In the secondary MLR, the stimulatory activity of B cells was found to be lower in aged SAMP1 mice but not in age-matched BALB/c or young SAMP1 mice. In addition, these age-related decreases in the stimulatory activity of APC were found to be related to changes in the surface density of major histocompatibility complex class II and intercellular adhesion molecule-1 (ICAM-1) (but not B7-1 or B7-2 molecule) on APC (DC and B cells).

Suppression of experimental autoimmune encephalomyelitis in Lewis rats by antibodies against CD2

The immunotherapeutic potential of three anti-rat CD2 monoclonal antibodies (mAb) (OX34, OX54, OX55) and the combination of OX54 with OX55 was tested in Lewis rat experimental autoimmune encephalomyelitis (EAE). In actively induced EAE, a single injection of OX34 2 days before immunization with myelin basic protein (MBP) in complete Freund's adjuvant (CFA) completely prevented or greatly attenuated EAE in all animals. Injection of OX54 acted moderately suppressive while OX55 or OX54/55 did not affect disease severity. Abrogation of EAE by OX34 was not restricted to its application before immunization. Therapeutic administration of all three mAb and the Ab combination from onset of first clinical signs efficiently blocked progression of disease and prevented all animals from developing hind limb paresis. In adoptive transfer EAE induced with in vitro activated cells of an encephalitogenic T helper line, clinical and histological signs were completely prevented by injection of OX34 on the day of cell transfer and 4 days later, underlining the strong impact of anti-CD2 mAb on the effector phase of disease. Immunocytofluorometric analysis of peripheral blood lymphocytes after a single Ab injection demonstrated that all mAb induced a variable degree of transient reduction in T cell numbers and modulation of CD2 antigens. In contrast to the other mAb, OX34 persisted on lymphocytes for at least 11 days, which may explain its unique suppressive effect on EAE after a single injection before immunization. The assumption that prophylactic administration of OX34 also inhibits MBP-induced EAE, due to persistence into the effector phase, was substantiated by the finding that none of the mAb prevented generation of an antigen-specific cellular response in MBP/CFA-immunized animals. Since none of the Ab induced T cell unresponsiveness or inhibited T cell activation by antigen- or Ab-mediated stimulation of the T cell receptor, we suggest that their marked action on the effector phase of EAE may rely on inhibition of T cell infiltration into the central nervous system. The demonstrated efficacy of these anti-CD2 mAb in EAE suggests a potential therapeutic role that may be equal to that of anti-CD4 or anti-T cell receptor Ab.

Cellular blebbing in superficial colonic epithelial cells occurring with murine graft-versus-host disease

Subnuclear blebbing of the superficial colonic epithelium, a rarely described light and electron microscopic change in graft-versus-host disease (GVHD), was studied in a murine model of GVHD. Severity of changes induced by transfer of various donor T cell subsets to irradiated, allogeneic recipients, and association with more severe alterations such as erosions and ulceration were evaluated. By light microscopy the basal region of the superficial enterocytes was greatly expanded by eosinophilic to amphophilic, flocculent, sometimes vacuolated material. By electron microscopy these changes were found to be organelle-poor, cytoplasm-filled protrusions from the basal surface of the epithelium. In this model, helper T cells (CD(4+)-enriched, CD(8+)-depleted T cells) transplanted after high dose irradiation were capable of causing the change suggesting cytokine responses may be involved in mediating the cellular injury seen histologically. Close association of blebbing and erosions suggest the blebbing may be the precursor to epithelial erosion or denudation seen in severe intestinal GVHD.

Antigen-specific human immunoglobulin production in SCID mice transplanted with human peripheral lymphocytes is dependent on CD4+ CD45RO+ T cells

Severe combined immunodeficient (SCID) mice, lacking mature T and B cells and virtually devoid of endogenous serum immunoglobulins, spontaneously produce large amounts of human immunoglobulin after transplantation with human peripheral blood lymphocytes (PBL). Moreover, after immunization with antigen an active immune response resulting in a production of specific antibodies can be induced. Here we report that human T cells must be co-transplanted with B cells into the SCID mice for immunoglobulin production to occur. Resting human B cells could be activated to immunoglobulin production in the absence of human monocytes and a specific antibody response to tetanus toxoid (TT) could be induced, suggesting that the human B cells could present antigen to T cells in the SCID environment. Production of human immunoglobulins, as well as specific antibodies, was obtained only if CD4+ T cells of the memory phenotype, i.e. expressing CD45RO, were present. No human immunoglobulin, either of IgM or of IgG isotype, was found in SCID sera if mice were co-transplanted with human B cells and CD45RA expressing CD4+ T cells. However, FACS analysis revealed that the transplanted CD45RA+ cells became activated and differentiated towards CD45RO+ cells within 1-2 weeks. These cells also gained the lymphokine gene expression pattern associated with CD45RO+ cells, as demonstrated by polymerase chain reaction (PCR) analysis, and could support immunoglobulin production in SCID mice transplanted with fresh B cells. In fact, after differentiation of CD4+ CD45RA+ T cells towards expression of CD45RO, either in vivo in the SCID mouse or in vitro, these cells could interact with and activate human B cells to immunoglobulin production. Furthermore, in vitro activated and differentiated CD4+ CD45RA+ T cells from vaccinated donors were also able to support production of TT-specific antibodies provided the antigen was administered.

Adoptive transfer of cloned T helper cells ameliorates periodontal disease in nude rats

We have previously described a T helper cell 2-type clone, A3, of rat T cells that provides help for antibody production to Actinobacillus actinomycetemcomitans in vitro and in vivo in normal (euthymic) isogeneic Rowett strain recipient rats. Adoptive transfer of this T helper cell clone to euthymic rats also protects them from periodontal bone loss induced by oral infection with A. actinomycetemcomitans. In the present study, to assess the cell requirement for protection, A3 clone T lymphocytes (10(6)) or naive lymph node (6 x 10(4)) T cells, or A3 plus naive lymph node T cells (6 x 10(4)) were adoptively transferred to groups (n = 7-9) of 30-day-old Rowett athymic nude (rnu/rnu) rats. All recipients were also immunized (intraperitoneally) with 10(7) killed A. actinomycetemcomitans on the day of T cell transfer and orally infected with these bacteria on each of the next 5 days. Recipients of the combined A3+lymph node T cell transfer showed significantly increased serum immunoglobulin G (IgG) and IgM antibody to A. actinomycetemcomitans and in vitro proliferation of spleen lymphocytes to A. actinomycetemcomitans as antigen compared with nude animals receiving lymph node T cells only. Although other possibilities are discussed, we inferred that these differences might be due to successful population of the congenitally athymic rats by A3 clone cells given with a small number of normal autologous naive lymph node T cells. The result of this co-transfer of naive T cells with the A3 clone cells seemed to be greatly increased antibody production and protection from periodontal bone loss.

The role of alloreactive cytotoxic and lymphokine-secreting T lymphocytes in the development of acute graft-versus-host disease

The development of acute graft-versus-host disease (GVHD) after allogeneic bone marrow transplantation is mediated by alloreactive donor T cells infused with the bone marrow inoculum. This review discusses the role and significance of host-specific cytotoxic and lymphokine-secreting donor T cells for the prediction and generation of acute GVHD.

Adoptive transfer of a Th2-like cell line prolongs MHC class II antigen disparate skin allograft survival in the mouse

The MHC class II alloantigen-reactive CD4+ Th2-like cell line, HR2, was established. It was derived from the spleen cells of C57BL/6 (B6) mice immune to an MHC class II-disparate mutant mouse, B6.CH-2bm12 (bm12) which carries the I-Abm12 antigen. This cell line, HR2, secretes IL-4 and IL-10 in an antigen-specific manner, and can also proliferate in an autocrine manner through IL-4. To investigate the in vivo role of this Th2-like CD4+ T cell line in transplantation immunity, an adoptive cell transfer study using the skin allograft system was performed. Skins grafted from bm12 to B6 were rejected at 12.1 +/- 0.6 days in control B6 mice which received no treatment. Whereas skin graft survival was prolonged in B6 experimental mice which had received 2 x 10(7) HR2 cells, 75% of the grafts survived for > 40 days. Moreover, since skin grafts from fully allogeneic third party donor BALB/c mice were rejected at 12.0 +/- 0.4 days by B6 mice which had received the same number of HR2 cells, it was demonstrated that HR2 is involved in the regulation of bm12 skin graft rejection. Furthermore, cytotoxic T lymphocyte (CTL) activity by spleen cells from HR2 transferred B6 mice was not induced even by in vitro secondary stimulation, although CTL activity was induced well in spleen cells of control B6 mice which had rejected the graft. The underlying mechanism has not been fully clarified; however, these results demonstrate that Th2-like CD4+ T cells suppress allograft rejection.

Th1 and Th2 CD4+ T cell clones specific for Plasmodium chabaudi but not for an unrelated antigen protect against blood stage P. chabaudi infection

The host protective immune response to blood stage malaria infection was studied using Plasmodium chabaudi chabaudi (P.chabaudi) in NIH mice. It has been shown previously that CD4+ cells are critically required for protection against erythrocytic infection. Mice lacking a functional CD4+ cell compartment suffer unremitting patent primary parasitemias for at least 60 days after infection. Here, we report that the adoptive transfer of eight P. chabaudi-specific CD4+ T cell clones of either the Th1 or Th2 type to mice rendered CD4-depleted by adult thymectomy and anti-CD4 monoclonal antibody therapy fully restored the ability of recipients to control challenge infection. Control Th1 and Th2 clones specific for an unrelated antigen, ovalbumin, were unable to confer a comparable level of protection in CD4-depleted mice, even though they received regular doses of the antigen. These data demonstrate that protective immunity to asexual P. chabaudi parasites can be mediated through immune CD4+ T cell clones of either the Th1 or the Th2 subset.

Resolution of murine chlamydial genital infection by the adoptive transfer of a biovar-specific, Th1 lymphocyte clone

MoPn-specific T-cell clones were isolated from a T-cell line that was capable of curing chlamydial genital infection by the Chlamydia trachomatis agent of mouse pneumonitis (MoPn) after adoptive transfer. Two clones (designated as 2.14-0 and 2.14-3) were characterized by flow cytometry techniques to be homogenous for L3T4, CD3, and alpha/beta T cell receptor (TcR) T-helper cell markers. The two clones were biovar specific, because they reacted to MoPn but not the Chlamydia psittaci agent of guinea pig inclusion conjunctivitis (GPIC) or C. trachomatis, serovar type E. Cytokine profile analysis, by a combination of bioassays, ELISA, and slot/Northern blotting for specific cytokine messenger RNAs, further revealed that cultures of antigen-stimulated clone 2.14-0 contained interleukin-2 (IL-2), tumor necrosis factor-alpha, and gamma interferon (a T helper 1 cell [Th1] profile). Clone 2.14-3 was also positive for gamma interferon, a level much lower than that of clone 2.14-0, and negative for IL-4 secretion, suggesting a Th1 profile as well. The ability of these clones to bring about the resolution of the chronic genital chlamydial infection of nude mice was tested by the adoptive transfer of 10(7) cells of each clone into the mice. By 4 weeks after cell transfer of clone 2.14-0, 81% of recipient nude mice (30 of 37) resolved the disease. In contrast, clone 2.14-3 or a control T-cell clone specific for a heterologous antigen were unable to resolve the infection in 20 recipients in each case, even after 100 days.(ABSTRACT TRUNCATED AT 250 WORDS)

Large-scale culture system of human CD4+ helper/killer T cells for the application to adoptive tumour immunotherapy

A simple method for the rapid expansion of human CD4+ T cells with both helper and killer functions was established. CD4+ T cells separated from peripheral blood mononuclear cells using immunomagnetic beads were stimulated with immobilised OKT-3 monoclonal antibody (mAb) plus recombinant interleukin 2 (rIL-2) in 96 well culture plates. After 6 day-culture, the CD4+ T cells were restimulated by immobilised OKT-3 mAb for an additional 24 h, then inoculated into concentrated rotary-tissue culture bag and cultured for further 9 days. This procedure yielded a 3000-fold increase in cell number (about 3-5 x 10(9) per bag). Most of the cells (over 96%) continued to express CD4+ antigen and retained their capacity to produce IL-2. The activated CD4+ T cells showed marked cytotoxicity against Fc receptor positive tumour cells in the presence of OKT-3 mAb. Moreover, we succeeded in a specific targeting of the expanded CD4+ helper/killer T cells to c-erb B-2 positive tumour cells by means of anti-CD3 x anti-c-erb B-2 bispecific antibody. These results suggested that our established simple system will be available for the expansion of large number of CD4+ helper/killer T cells which may provide an efficient strategy for adoptive tumour immunotherapy.

Concomitant treatment of MBT-2 bladder tumour by tumour necrosis factor alpha and interferon alpha in conjunction with delayed type hypersensitivity immunotherapy

In our previous study [9], we reported the anti-tumour effect of TNF on mouse bladder tumour (MBT-2) both in vivo and in vitro. Inoculation of a single dose of TNF alone caused significant but transient tumour growth inhibition. Subsequent repeated doses of TNF did not sustain or augment the anti-tumour effect. The current experiments were undertaken to assess the anti-tumour activity of (i)-concomitant treatment of TNF-A and IFN-A against MBT-2 bladder tumour and (ii)-concomitant TNF + IFN-A treatment in conjunction with T-DTH (delayed-type hypersensitivity) immunotherapy. Systemic administration of multiple doses of TNF + IFN-A in vivo caused initial partial tumour regression followed by tumour growth inhibition up to 14 days following treatment. This combined treatment showed an enhanced anti-tumour effect compared to TNF-A treatment alone. Immunotherapy of MBT-2 tumour-bearing mice with T-DTH "immune" effector cells alone did not cause significant tumour growth inhibition. In contrast, concomitant administration of both T-DTH effector cells and TNF + IFN-A in MBT-2 tumour-bearing mice resulted in significant tumour growth inhibition for up to 16 days. The immune effector cells conferring immunotherapy were isolated from the spleens of tumour-immunized, "DTH-primed" animals and were characterized as Lyt 1+2- helper/DTH T cells (CD4+ phenotype). These cells mediate both DTH response to MBT-2 tumour antigens as well as anti-MBT-2 tumour protection. In vitro treatment of the "immune" cells with TNF-A resulted predominantly in the proliferation of Lyt 1+ T cells versus Lyt 2+ cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Antigen-specific T-helper cells abrogate suppression in Trypanosoma cruzi-infected mice

The ability of antigen-specific T-helper (Th) cells to enhance direct plaque-forming cell responses in spleen cells from Trypanosoma cruzi-infected C57BL/6 mice was investigated at various times during the course of infection from day 7 to day 230. The injection of antigen-specific Th cells in vivo or the addition of antigen-specific Th cells in vitro was effective in enhancing direct plaque-forming cell responses, except at the time of the most intense suppression during the acute phase of infection (i.e., day 28). The ability of antigen-specific Th cells to overcome nonspecific immunosuppression was due not only to the activity of antigen-specific Th cells added to Mishel-Dutton cultures but also to activation of resident T cells. Thus, antigen-specific Th cells and resident T cells act in concert to produce enhanced direct plaque-forming cell responses. The effect of plastic-adherent spleen cells from infected mice on the ability of antigen-specific Th cells to stimulate anti-sheep erythrocyte responses of normal spleen cells was examined because macrophages have been shown to have an immunoregulatory role during the course of experimental American trypanosomiasis. Increasing numbers of macrophages from infected mice caused increased immunosuppression of normal spleen cells that could not be overcome with the addition of primed Th cells. It can be concluded from these data that antigen-specific Th cells can potentiate immune responses in mice infected with T. cruzi but that highly active suppressor macrophages can inhibit the expression of these primed Th cells.

Induction of anti-allo-class I H-2 tolerance by inactivation of CD8+ helper T cells, and reversal of tolerance through introduction of third-party helper T cells

The intravenous sensitization of C57BL/6 (B6) mice with class I H-2-disparate B6-C-H-2bm1 (bm1) spleen cells resulted in the abrogation of CD8+ T cell-mediated anti-bm1 (proliferative and interleukin 2-producing) T helper (Th) cell activities. In vitro stimulation of lymphoid cells from these mice with bm1 cells, however, generated a reduced, but appreciable, anti-bm1 cytotoxic T lymphocyte (CTL) response. Moreover, the anti-bm1 CTL response, upon stimulation with [bm1 x B6-C-H-2bm12 (bm12)]F1 spleen cells, was enhanced when compared with the response induced upon stimulation with bm1 cells. These in vitro results were reflected on in vivo graft rejection responses; bm1 skin grafts engrafted in the bm1-presensitized B6 mice exhibited prolonged survival, whereas (bm1 x bm12)F1 grafts placed collateral to bm1 grafts (dual engrafted mice) inhibited the tolerance to bm1. In the B6 mice 1-2 d after rejecting the bm1 grafts, anti-bm1 Th activities remained marginal, whereas potent anti-bm1 CTL responses were found to be generated from their spleen cells. Administration in vivo of anti-CD4 antibody into bm1-presensitized, dual graft-engrafted mice prolonged bm1 graft survival and interfered with enhanced induction of anti-bm1 CTL activity. These results indicate that anti-class I alloantigen (bm1) tolerance as induced by intravenous presensitization with the relevant antigens is not ascribed to the elimination of CD8+ CTL precursors, but to the specific inactivation of CD8+ Th cells, whose function can be bypassed by activating third-party Th cells.

Host resistance to cyclosporine induced syngeneic graft-versus-host disease. Requirement for two distinct lymphocyte subsets

Cyclosporine is crucial for the prevention of organ allograft rejection and allogeneic graft-vs-host disease (GVHD). Despite its potent immunosuppressive activity, cyclosporine elicits a T cell-mediated autoimmune syndrome after autologous or syngeneic bone marrow transplantation, which has been termed syngeneic GVHD (SGVHD). Recent studies have shown that for disease manifestation, a cytoxan and radiation-sensitive T cell dependent host resistance mechanism must be eliminated, allowing the clonal expansion of autoreactive cells. This report characterizes the autoregulatory lymphocyte population, present in normal animals, capable of inhibiting the adoptive transfer of SGVHD. First, twice the number of unfractionated splenocytes from normal animals to those from autoimmune donors ensured complete inhibition of the adoptive transfer of immune reactivity. Second, the phenotype of this host resistance mechanism in normal splenocytes involves dual regulatory T cell subsets. A helper/inducer subset (W3/25+) must be cotransferred with a cytotoxic/suppressor subset (OX8+) in a ratio that approximates the normal ratio in normal unfractionated splenocytes in order to affect inhibition of the transfer of SGVHD. Moreover the specific inducer regulatory activity resides in the OX22-, W3/25+ subset of Th cells.

Lymphocyte vaccination against experimental autoimmune encephalomyelitis: evaluation of vaccination protocols

Repeated vaccination with encephalitogenic but not other T cell lines could effect marked resistance to 'active' experimental autoimmune encephalomyelitis (EAE) induced by injection of GP-BP in adjuvant. Partial resistance to active EAE was observed in rats recovered from 'passive' line-mediated EAE and in rats vaccinated with T cells attenuated by irradiation or ganglioside treatment. However, no resistance was observed in animals given low doses of activated encephalitogenic T cells. Treatment with hydrostatic pressure alone was found to be ineffective as a means of attenuation, and vaccination with pressure-treated encephalitogenic T cells actually induced mild signs of EAE. However, vaccination with cells that were first pressure treated and then irradiated prevented both clinical and histologic signs of active EAE. In contrast, protection against passive EAE appeared to be clonotypic. Lymphocyte vaccination induced delayed type hypersensitivity (DTH) reactions against autologous T cells, mostly to shared antigens, demonstrating the immunogenicity of multiple antigens on the vaccinating cells.

Intraocular trafficking of lymphocytes in locally induced experimental autoimmune uveoretinitis (EAU)

Experimental autoimmune uveoretinitis (EAU) was induced in naive Lewis rats by intravitreal adoptive transfer of 10(6) long-term S-antigen (S-Ag)-specific syngeneic T-lymphocyte lines of helper/inducer phenotype (ThS). These cells were stimulated with the T-cell mitogen concanavalin A (Con A) in culture for 48 hr and subsequently labeled with tritiated thymidine. Lymph node cells (LNC) cultured in parallel were used as controls. Histopathology and light microscopic autoradiography of the ocular tissue was performed at several time points to analyze the cell migration in relation to the development of EAU. The disappearance of both types of lymphocytes from the vitreous was similar and large numbers of host leukocytes were attracted into the vitreous. However, significantly more S-Ag-specific cells penetrated the retina and induced EAU (P less than 0.008). These results suggest that the development of EAU by intravitreal injection of S-Ag-specific T lymphocytes occurs by the migration of antigen-specific cells into the retina and recognition of the specific antigen, with subsequent release of soluble mediators that interact with the host effector cells, ultimately leading to specific photoreceptor damage.

A suppressor T-lymphocyte cell line for autoimmune encephalomyelitis

Experimental allergic encephalomyelitis (EAE) is a model for the in vitro and in vivo study of T-cell activation. It is an autoimmune disease mediated by T lymphocytes of the helper T-cell (Th) subset. After sensitization to guinea-pig myelin basic protein in complete Freund's adjuvant, Lewis rats develop an autoimmune response to central nervous system (CNS) myelin basic protein, manifested clinically as paralysis and histologically by a perivascular mononuclear cell infiltrate of the CNS parenchyma. Suppressor cell regulation of EAE has long been suspected because Lewis rats, which spontaneously recover from active disease, are resistant to reinduction of active EAE, even though effector T-cell lines can be rescued from these recovered rats. Using cyclosporin A, an immunosuppressive agent believed to inhibit Th cell function, suppressor T-cell (Ts) lines have now been generated from recovered Lewis rats. These Ts cells, when admixed with guinea pig myelin basic protein-specific Th cells, will prevent the adoptive transfer of EAE. The Ts cells appear to be CD4+, which explains previous observations that CD8+ lymphocytes are not important in the recovery of EAE in the rat. This is the first direct demonstration of Ts-cell regulation of EAE.

Essential requirement of I-A region-identical host bone marrow or bone marrow-derived cells for tumor neutralization by primed L3T4+ T cells

The antitumor activity of Meth A-hyperimmunized BALB/c mouse spleen cells (Meth A-Im-SPL) was assayed by the Winn test in H-2 incompatible bone marrow chimeras in closed colony CD-1 (nu/nu), inbred DDD/1(nu/nu) (H-2s), or inbred BALB/c(nu/nu) (H-2d) mice as recipients. We found that Meth A-Im-SPL suppressed Meth A growth in the chimera nude mice which were reconstituted with bone marrow cells of the H-2d haplotype (i.e., BALB/c, DBA/2 and B10.D2), but not in the chimeras which were reconstituted with bone marrow cells of the H-2a, H-2b, or H-2k haplotype (i.e., B10.A, B10, and B10.BR). These results suggested that H-2 restriction occurred between Meth A-Im-SPL and bone marrow or bone marrow-derived cells in tumor neutralization. Furthermore, Meth A-Im-SPL did not suppress Meth 1 tumors (antigenically distinct from Meth A tumors) in the presence or absence of mitomycin C-treated Meth A in a Winn assay. These results suggested that there is tumor specificity in the "effector phase" as well as in the "induction phase". The phenotype of the effectors in the Meth A-Im-SPL was Thy-1.2+ and L3T4+, because Meth A-Im-SPL lost their antitumor activity with pretreatment with anti-Thy-1.2 monoclonal antibody (mAb) and complement or anti-L3T4 mAb and complement, but not with anti-Lyt-2.2 mAb and complement or complement alone. Positively purified L3T4+ T cells from Meth A-Im-SPL (Meth A-Im-L3T4), obtained by the panning method, suppressed the tumor growth in the chimera nude mice which were reconstituted with bone marrow cells of B10.KEA2 mice (that were I-A region-identical with Meth A-Im-L3T4 cells but not others in H-2) as well as B10.D2 cells (that were fully identical with Meth A-Im-L3T4 cells in H-2). We conclude that Meth A-Im-SPL (L3T4+) neutralized the tumors in collaboration with I-A region-identical host bone marrow or bone marrow-derived cells, and the neutralization was not accompanied by the "bystander effect."