Comparative analysis of B7-1 and B7-2 expression in Langerhans cells: differential regulation by T helper type 1 and T helper type 2 cytokines

IFN-γ: A cytokine at the right time, is in the right place

Interferon gamma has long been studied as a critical mediator of tumor immunity. In recent years, the complexity of cellular interactions that take place in the tumor microenvironment has become better appreciated in the context of immunotherapy. While checkpoint inhibitors have dramatically improved remission rates in cancer treatment, IFN-γ and related effectors continue to be identified as strong predictors of treatment success. In this review, we provide an overview of the multiple immunosuppressive barriers that IFN-γ has to overcome to eliminate tumors, and potential avenues for modulating the immune response in favor of tumor rejection.

Allergen-specific subcutaneous immunotherapy in allergic asthma: immunologic mechanisms and improvement

Allergic asthma is a disease characterized by persistent allergen-driven airway inflammation, remodeling, and airway hyperresponsiveness. CD4(+) T-cells, especially T-helper type 2 cells, play a critical role in orchestrating the disease process through the release of the cytokines IL-4, IL-5, and IL-13. Allergen-specific immunotherapy (SIT) is currently the only treatment with a long-term effect via modifying the natural course of allergy by interfering with the underlying immunological mechanisms. However, although SIT is effective in allergic rhinitis and insect venom allergy, in allergic asthma it seldom results in complete alleviation of the symptoms. Improvement of SIT is needed to enhance its efficacy in asthmatic patients. Herein, the immunoregulatory mechanisms underlying the beneficial effects of SIT are discussed with the ultimate aim to improve its treatment efficacy.

Application of a Systems Biology Approach to Skin Allergy Risk Assessment

We have developed an in silico model of the induction of skin sensitisation, in order to characterise and quantify the contribution of each pathway to the overall biological process. This analysis has been used to guide our research on skin sensitisation and in vitro test development programmes, and provides a theoretical rationale for the interpretation and integration of non-animal predictive data for risk assessment (RA) purposes. The in vivo mouse Local Lymph Node Assay (LLNA) is now in widespread use for the evaluation of skin sensitisation potential and potency. Recent changes in European Union (EU) legislation (i.e. the 7th Amendment to the EU Cosmetics Directive) have made the development of non-animal approaches to provide the data for skin sensitisation RA a key business need. Several in vitro predictive assays have already been developed for the prediction of skin sensitisation. However, these are based on the determination of a small number of pathways within the overall biological process, and our understanding of the relative contribution of these individual pathways to skin sensitisation induction is limited. To address this knowledge gap, a “systems biology” approach has been used to construct a computer-based mathematical model of the induction of skin sensitisation, in collaboration with Entelos, Inc. The biological mechanisms underlying the induction phase of skin sensitisation are represented by nonlinear ordinary differential equations and defined by using information from over 500 published papers. By using the model, we have identified knowledge gaps for future investigative research, and key factors that have a major influence on the induction of skin sensitisation (e.g. TNF-α production in the epidermis). The relative contribution of each of these key pathways has been assessed by determining their contributions to the overall process (e.g. sensitiser-specific T-cell proliferation in the draining lymph node). This information provides a biologically-relevant rationale for the interpretation and potential integration of diverse types of non-animal predictive data. Consequently, the Skin Sensitisation Physiolab® (SSP) platform represents one approach to integration that is likely to prove an invaluable tool for hazard evaluation in a new framework for consumer safety RA.

Improving antitumor immune responses by circumventing immunoregulatory cells and mechanisms

Although numerous immunotherapeutic strategies have been studied in patients with cancer, consistent induction of clinical responses remains a formidable challenge. Cancer vaccines are often successful at generating elevated numbers of tumor-specific T lymphocytes in peripheral blood, however, despite this, tumors usually continue to grow unabated. Recent evidence suggests that endogenous regulatory cells, known to play a major role in the induction of immune tolerance to self and prevention of autoimmunity, as well as suppressive myeloid cells invoked in the tumor-bearing state, may be largely responsible for preventing effective antitumor immune responses. This review will focus on the major regulatory cell subtypes, including CD4(+)CD25(+) T-regulatory cells, type 1 regulatory T cells, natural killer T cells, and immature myeloid cells. Studies in humans and in animal models have shown a role for all of these cells in tumor progression, although the mechanisms by which they act to suppress immunity remain largely undefined. Elucidation of the dominant molecular mechanisms mediating immune suppression in vivo will allow more precise targeting of the relevant regulatory cell populations, as well as the development of novel strategies and clinical reagents that will directly block molecules that induce the suppression of antitumor immunity.

CD86 molecule is a specific marker for canine monocyte-derived dendritic cells

In this study, canine monocyte-derived dendritic cells (cMo-DC) were produced in presence of canine GM-CSF (cGM-CSF) and canine IL-4 (cIL-4), and they were characterized by their dendritic morphology, MLR functionality and phenotype. We noticed that cMo-DC were labelled with three anti-human CD86 (FUN-1, BU63 and IT2.2 clones), whereas resting and activated lymphocytes or monocytes were not stained. CD86 expression was induced by cIL-4 and was up-regulated during the differentiation of the cMo-DC, with a maximum at day 7. Furthermore, cMo-DC were very potent even in low numbers as stimulator cells in allogeneic MLR, and BU63 mAb was able to completely block the cMo-DC-induced proliferation in MLR. We also observed that cMo-DC highly expressed MHC Class II and CD32, but we failed to determine their maturation state since the lack of commercially available canine markers. Moreover, cMo-DC contained cytoplasmic periodic microstructures, potentially new ultrastructural markers of canine DC recently described. In conclusion, this work demonstrates that the CD86 costimulatory marker is now usable for a better characterization of in vitro canine DC.

T-cell costimulatory capacity of oral and skin epithelial cells in vitro: presence of suppressive activity in supernatants from skin epithelial cell cultures

Oral Langerhans cells (LC) have better T-cell costimulatory capacity than skin LC. In this study factors affecting this capacity have been assessed in a mixed epithelial cell lymphocyte reaction (MELR) assay. Flow cytometry analysis of freshly recovered cells revealed major histocompatibility complex (MHC) class II molecule expression on 7.5% of the oral epithelial cells and 9.7% of the skin epithelial cells. Monoclonal anti class II antibodies significantly reduced the T-cell proliferation in the MELR. Pretreatment of skin epithelial cells with interleukin-1beta, tumour necrosis factor-alpha or interferon (IFN)-gamma did not affect the MELR proliferation, but incubation with IFNgamma significantly suppressed the T-cell response. Transfer of supernatants from cultures of skin epithelial cells and allogeneic T cells to cultures of oral epithelial cells and T cells resulted in a reduced T-cell proliferation while supernatants from oral epithelial cells and T cells did not reduce proliferation. The higher proliferation in cultures of T cells and oral epithelial cells than in cultures containing skin epithelial cells may be due to the presence of a suppressive factor in the skin epithelial cell suspensions.

IL-10 Promoter nt - 1082A/G Polymorphism and Human Papillomavirus Infection in Cytologic Abnormalities of the Uterine Cervix

The role of A/G polymorphism at nucleotide -1082 in the interleukin-10 (IL-10) promoter was assessed by following the disease course of 253 patients who had had a routine diagnostic Hybrid Capture human papillomavirus (HPV) test because of cytologic or colposcopic abnormalities of the uterine cervix. At baseline, 97 (78%) of the 125 high-risk HPV-positive and 83 (65%) of the 128 HPV-negative patients had equivocal cytologic atypia classified as P3 by the Papanicolaou classification, and the rest of the patients had mild colposcopic atypia with cytologic results of no oncogenic significance. In the high-risk HPV-infected patients, the frequency distribution of the nt -1082 genotypes (A/A: 28%; A/G: 52%; G/G: 20%) did not differ significantly from that in the controls (A/A: 25%; A/G: 51%; G/G: 24%; p = 0.70). On the other hand, the nt -1082 G allele tended to decrease susceptibility to equivocal cytologic atypia unrelated to HPV infection (A/G: OR = 0.56 [95% CI: 0.31-1.02], G/G: OR = 0.27 [95% CI: 0.11-0.63], p for trend = 0.05). With respect to the development of high-grade cervical intraepithelial neoplasia (CIN), the established risk factors, such as high-risk HPV infection (RR = 104.6, 95% CI: 14.2-769.9) and cytologic atypia (RR = 9.6, 95% CI: 2.34-39.7) but not the various nt -1082 genotypes (A/A: reference; A/G: RR = 1.11 [95% CI: 0.59-2.08]; G/G: RR = 0.62 [95% CI: 0.25-1.50]) were found to increase the risk for high-grade CIN. In conclusion, the nt -1082 polymorphism had no influence on the early phase of cervical carcinogenesis but may determine different susceptibilities to cervical abnormalities unrelated to HPV infection.

Altered cutaneous immune parameters in transgenic mice overexpressing viral IL-10 in the epidermis

IL-10 is a pleiotropic cytokine that inhibits several immune parameters, including Th1 cell-mediated immune responses, antigen presentation, and antigen-specific T cell proliferation. Recent data implicate IL-10 as a mediator of suppression of cell-mediated immunity induced by exposure to UVB radiation (280-320 nm). To investigate the effects of IL-10 on the cutaneous immune system, we engineered transgenic mice that overexpress viral IL-10 (vIL-10) in the epidermis. vIL-10 transgenic mice demonstrated a reduced number of I-A(+) epidermal and dermal cells and fewer I-A(+) hapten-bearing cells in regional lymph nodes after hapten painting of the skin. Reduced CD80 and CD86 expression by I-A(+) epidermal cells was also observed. vIL-10 transgenic mice demonstrated a smaller delayed-type hypersensitivity response to allogeneic cells upon challenge but had normal contact hypersensitivity to an epicutaneously applied hapten. Fresh epidermal cells from vIL-10 transgenic mice showed a decreased ability to stimulate allogeneic T cell proliferation, as did splenocytes. Additionally, chronic exposure of mice to UVB radiation led to the development of fewer skin tumors in vIL-10 mice than in WT controls, and vIL-10 transgenic mice had increased splenic NK cell activity against YAC-1targets. These findings support the concept that IL-10 is an important regulator of cutaneous immune function.

Characterization of B-1b cells as antigen presenting cells in the immune response to gp43 from Paracoccidioides brasiliensis in vitro

Antigen presentation is an essential stage in the development of immune response to a specific antigen. This response can lead to the production of antibodies and/or effector T lymphocyte activation. Macrophages, dendritic cells and B-lymphocytes, among others, act as antigen presenting cells. B-lymphocytes capture antigenic particles through a surface receptor of IgM nature. The interaction IgM-antigen leads to endocytosis of the complex and antigen processing which culminates in presentation of the antigen on the cell surface associated with a class II MHC molecule. At least three B cell subsets, B-1a (Ly-1B), B-1b and B-2, are present in the mouse periphery. B-1a and B1-b cells represent a small population in the adult spleen and are abundant in the peritonial and pleural cavities. It has been demonstrated in our laboratory that B-1b cells spontaneously proliferated in stationary cultures of adherent peritonial cells. Further, that these cells migrate to a non-specific inflammatory focus. Based on these findings, we investigated whether these cells are antigen presenting cells in vitro using as antigenic stimulus gp43 from Paracoccidioides brasiliensis. Results showed that B1-b cells express constitutively high levels of class II MHC and costimulatory molecules inducing an efficient proliferation of gp43 sensitized T lymphocytes.

Regulation of major histocompatibility complex class II synthesis by interleukin-10

We have shown previously that interleukin-10 (IL-10) blocks the development and T-cell stimulatory capacity of human monocyte-derived dendritic cells, without apparently down-regulating the surface expression of co-stimulatory molecules or human leucocyte antigen (HLA) molecules. In the majority of donors (60%), the cell surface levels of HLA-DR actually increased upon IL-10 treatment. Here we have shown that IL-10 does not regulate HLA-DR transcription as assessed by polymerase chain reation. Epifluorescence microscopy analysis showed that IL-10 primarily increased the intracellular pool of HLA-DR. In fact, IL-10 directly increased HLA-DR protein synthesis. However, IL-10 did not significantly alter the synthesis of invariant chain (Ii), which plays a crucial role in the assembly, transport and loading of newly formed HLA class II molecules, nor the amount of Ii reaching the cell-surface. In contrast, IL-10 increased the amount of HLA-DR-bound Iip33 shortly after the HLA-DR complex assembly. We postulate that, upon IL-10 treatment, immature Ii-associated HLA II molecules can still transit to the cell surface as they do in immature dendritic cells and recycle to the intracellular space, where they accumulate. A higher proportion of Ii-associated HLA-DR, coupled to increased membrane recycling, may contribute to the lower T-cell stimulatory capacity of IL-10-treated dendritic cells.

Roles of cytotoxic T-lymphocyte-associated antigen-4 in the inductive phase of oral tolerance

To elucidate the roles of cytotoxic T-lymphocyte-associated antigen-4 (CTLA-4) in oral tolerance, we studied the consequences of CTLA-4 blockade during the inductive phase of oral tolerance using a transgenic T-cell transfer model. We found that CTLA-4 blockade significantly accelerated cell cycle progression of antigen-specific T cells and dramatically increased their numbers in lymphoid organs following oral administration of ovalbumin (OVA). In mice fed with OVA, only approximately 35% of specific T cells underwent more than four cycles of cell division. This was increased to 65% in mice fed with OVA and treated with a blocking anti-CTLA-4 monoclonal antibody (mAb). The OVA-specific T cells in the latter group were localized primarily in the T-cell zones of the mesenteric lymph nodes and Peyer's patches with a few penetrated into B-cell follicles. Nevertheless, both faecal anti-OVA immunoglobulin A (IgA) and seral anti-OVA immunoglobulin G (IgG) were produced in anti-CTLA-4 mAb-treated mice. These results suggest that CTLA-4 limits the degree of T-cell activation by blocking cell cycle progression during the inductive phase of oral tolerance. In the absence of the CTLA-4 signal, mucosal exposure of antigen induces heightened T-cell activation and expansion, which in turn promotes the production of antigen-specific antibodies.

Immunity to oncogenic human papillomaviruses

The establishment of human papillomavirus (HPV) infection as a major cause of several human cancer forms, notably cervical cancer, has spurred development of prophylactic and/or therapeutic HPV vaccines for prevention of cervical neoplasia. Knowledge of the immunity to HPV forms the basis for such endeavors.

METHOD

A literature review of humoral and cellular immunity to HPV. The overview on human leukocyte antigen (HLA) and cervical cancer was expanded to a formal metaanalysis, where relevant articles were located by Medline search and citation analysis and graded by preassigned quality criteria on study design.

RESULTS

The antibody response to the HPV particle is dominated by a neutralizing antibody response to a typespecific, conformationally dependent immunodominant epitope. Vaccines based on viral particles lacking the viral genome (virus-like particles, VLPs) have been highly successful in preventing and treating HPV infection in several animal model systems. In humans, the serum antibody response to VLPs is stable over time, also after the HPV infection has been cleared, resulting in HPV serology being used as a marker of cumulative HPV exposure in spite of the fact that a significant proportion of HPV-exposed subjects fail to seroconvert. More than 90% of HPV infections will clear spontaneously. The factors that determine whether an HPV infection is cleared or persists and increases the risk for cancer are not known, but cellular immunity is implicated. Several HLA class II haplotypes are associated with cervical cancer: DQw3 increases and DR13 decreases the risk for cervical cancer in general (odds ratios (OR) and 95% confidence intervals (CI): 1.25(1.15-1.37) and 0.69 (0.56-0.85), respectively); DR15 increases the risk for HPV16-carrying cancer (OR: 1.47; CI: 1.20-1.81); and DR7 may be either protective or increase the risk. Most cervical cancers have downregulated the expression of at least one HLA class I antigen, whereas class II expression is increased in infected epithelium. A Th2 cytokine profile is associated with progression to cervical cancer. HPV-antigen-specific proliferative responses have been detected in many studies, although it is not entirely clear whether these responses are HPV type specific or may be cross-reactive between HPV types. Specific cytotoxic T lymphocyte (CTL) responses were originally reported in only a minority of infected subjects, typically cancer patients, but with advancing technology, specific CTLs can be stimulated from about half of the women with HPV-carrying disease. In animal model systems, CTL responses can mediate clearance.

CONCLUSION

The antibody response to HPV is a mediator of type-specific protective immunity, which forms the basis for prophylactic vaccine candidates. The cellular immunity to HPV is implicated as an important factor in cervical carcinogenesis, but the main targets and types of responses that mediate HPV clearance are not established.

Dendritic cells: immune regulators in health and disease

Dendritic cells (DCs) are bone marrow-derived cells of both lymphoid and myeloid stem cell origin that populate all lymphoid organs including the thymus, spleen, and lymph nodes, as well as nearly all nonlymphoid tissues and organs. Although DCs are a moderately diverse set of cells, they all have potent antigen-presenting capacity for stimulating naive, memory, and effector T cells. DCs are members of the innate immune system in that they can respond to dangers in the host environment by immediately generating protective cytokines. Most important, immature DCs respond to danger signals in the microenvironment by maturing, i.e., differentiating, and acquiring the capacity to direct the development of primary immune responses appropriate to the type of danger perceived. The powerful adjuvant activity that DCs possess in stimulating specific CD4 and CD8 T cell responses has made them targets in vaccine development strategies for the prevention and treatment of infections, allograft reactions, allergic and autoimmune diseases, and cancer. This review addresses the origins and migration of DCs to their sites of activity, their basic biology as antigen-presenting cells, their roles in important human diseases and, finally, selected strategies being pursued to harness their potent antigen-stimulating activity.

Interleukin-10 gene promoter polymorphisms in multiple myeloma

Multiple myeloma (MM) is a B-cell malignancy characterized by an accumulation of malignant plasma cells in the bone marrow. It is unclear whether genetic background could have an etiological impact on MM or influence the course of the disease. Interleukin-10 (IL-10) has been implicated in the growth and differentiation of normal B cells, and has also been shown to enhance the proliferation of MM cells. To address the putative involvement of IL-10 genetic variation in MM, we analyzed previously defined loci for bi-allelic polymorphism at position -1082 and two microsatellite loci (IL10.G and IL10.R) in the IL-10 promoter region. Seventy-three patients with MM, 27 with monoclonal gammopathy of undetermined significance, and 109 ethnically matched individuals as controls were included in the study. Significantly increased frequencies of the IL10.G genotype 136/136 and the IL10.R genotype 112/114, in addition to a decreased frequency of the IL10.R genotype 114/116, were found among the MM patients. Increased production of IL-10 was detected in the supernatants of lipopolysaccharide-stimulated peripheral blood mononuclear cells from MM patients who were homozygotes (136/136) and heterozygotes (136/non-136) for the IL10.G allele 136, as compared with the other IL10.G genotype carriers (non-136/non-136). These results suggest that the genetic variation in the IL-10 promoter region may play a role in the development of MM.

Differentiation of Langerhans cells in Langerhans cell histiocytosis

Langerhans cell histiocytosis (LCH) consists of lesions composed of cells with a dendritic Langerhans cell (LC) phenotype. The clinical course of LCH ranges from spontaneous resolution to a chronic and sometimes lethal disease. We studied 25 patients with various clinical forms of the disease. In bone and chronic lesions, LCH cells had immature phenotype and function. They coexpressed LC antigens CD1a and Langerin together with monocyte antigens CD68 and CD14. Class II antigens were intracellular and LCH cells almost never expressed CD83 or CD86 or dendritic cell (DC)-Lamp, despite their CD40 expression. Consistently, LCH cells sorted from bone lesions (eosinophilic granuloma) poorly stimulated allogeneic T-cell proliferation in vitro. Strikingly, however, in vitro treatment with CD40L induced the expression of membrane class II and CD86 and strongly increased LCH cell allostimulatory activity to a level similar to that of mature DCs. Numerous interleukin-10-positive (IL-10(+)), Langerin(-), and CD68(+) macrophages were found within bone and lymph node lesions. In patients with self-healing and/or isolated cutaneous disease, LCH cells had a more mature phenotype. LCH cells were frequently CD14(-) and CD86(+), and macrophages were rare or absent, as were IL-10-expressing cells. We conclude that LCH cells in the bone and/or chronic forms of the disease accumulate within the tissues in an immature state and that most probably result from extrinsic signals and may be induced to differentiate toward mature DCs after CD40 triggering. Drugs that enhance the in vivo maturation of these immature DCs, or that induce their death, may be of therapeutic benefit.

Human epidermal Langerhans' cells are targets for the immunosuppressive macrolide tacrolimus (FK506)

BACKGROUND

The immunosuppressive macrolide tacrolimus (FK506) has been shown to inhibit allergic contact dermatitis in animal models as well as in human beings. More recently, successful treatment of atopic dermatitis with an ointment containing tacrolimus has been reported.

OBJECTIVES

We explored the effects of this compound on epidermal Langerhans' cells (LCs), which are known to play an important pathophysiologic role in inflammatory skin diseases.

METHODS

The expression of the intracellular FK506 binding protein (FKBP12) was monitored on freshly isolated and cultured epidermal LCs. Phenotyping and functional exploration of LCs treated with different concentrations of tacrolimus and beta-methasone valerate (betaMv) were performed.

RESULTS

FKBP12 is expressed in freshly isolated LCs but is lost while they are maturating into mature dendritic cells. Tacrolimus inhibited the expression of IL-2R (CD25) and of the costimulatory molecules CD80 (B7.1) and CD40. Expression of MHC class I and II was also affected, whereas CD86 (B7.2) expression was not altered. In contrast, betaMv strongly increased the expression of CD25. Paradoxically, while decreasing CD40 and MHC class I expression, betaMv significantly increased the expression of MHC class II, CD80, and CD86 on cultured LCs but impaired their allostimulatory activity. Tacrolimus was about 100 times more potent than betaMv at inhibiting LC stimulatory function.

CONCLUSION

Tacrolimus can exert immunopharmacologic alterations on LCs, which may account, at least in part, for the therapeutic effect of this compound in eczematous skin diseases.

An intra-Peyer's patch gene transfer model for studying mucosal tolerance: distinct roles of B7 and IL-12 in mucosal T cell tolerance

Development of mucosal immunity and tolerance requires coordinated expression of a number of genes within the mucosa-associated lymphoid tissue (MALT). To study the roles of these genes in the MALT, we have established a MALT-specific gene transfer model using replication-defective adenovirus as vector. In this model, the target gene of interest is directly delivered into the Peyer's patch by intra-Peyer's patch injection of the recombinant virus. Using this gene transfer model, we investigated the roles of B7-1 and IL-12 in the development of mucosal tolerance. We found that intra-Peyer's patch injection of OVA induced Ag-specific T cell hyporesponsiveness, as manifested by decreased T cell proliferation and IL-2/IFN-gamma production upon subsequent immune challenge. Intra-Peyer's patch B7-1 gene transfer at the time of OVA administration partially reversed the inhibition of T cell proliferation and IL-2 secretion, but had no effect on IFN-gamma production. By contrast, intra-Peyer's patch IL-12 gene transfer completely restored T cell proliferation and IFN-gamma secretion and partially reversed IL-2 inhibition. Using an adoptive TCR transgenic model, we further demonstrated that B7 and IL-12 played distinct roles during the inductive phase of mucosal tolerance. B7 selectively increased T cell proliferation and IL-2 secretion without affecting IFN-gamma production, whereas IL-12 increased both IL-2 and IFN-gamma production. These results indicate that B7 alone may not be sufficient to abrogate mucosal tolerance, and that cytokines such as IL-12 may also be required. Based on these findings, we propose a new model to explain the paradoxical roles of B7 in mucosal immunity and tolerance.

Association of B7-1 co-stimulation with the development of graft arterial disease. Studies using mice lacking B7-1, B7-2, or B7-1/B7-2

To investigate the roles of B7-1 and/or B7-2 co-stimulatory molecule in the development of graft arterial disease (GAD), major histocompatibility complex (MHC) class II-mismatched allograft hearts were transplanted into wild-type, B7-1(-/-), B7-2(-/-), or B7-1/B7-2(-/-) recipient mice. Grafts were explanted at 4 or 8 weeks and used for histological and immunohistochemical analyses, RNase protection assay, and flow cytometry of graft infiltrating cells. Grafts in wild-type recipients showed macrophage, recipient MHC class II, and B7 molecule co-localization by immunohistochemistry to GAD lesions. Flow cytometry revealed that CD11b(+) and MHC class II(+) graft infiltrating cells expressed B7-1 more than B7-2, whereas B7-2 expression was predominant in CD11b(-) cells at 4 and 8 weeks. GAD was significantly attenuated in the allografts in B7-1(-/-) and B7-1/B7-2(-/-) but not in B7-2(-/-) recipients compared to wild-type hosts. Interferon-gamma mRNA levels were comparable in all graft combinations, whereas interleukin-4 mRNA levels decreased in grafts in B7-2 deficient hosts, but did not correlate with GAD attenuation. The findings indicate distinct roles for B7-1 and B7-2 co-stimulatory molecules in the development of GAD, potentially because of differential expression of B7-1 and B7-2 molecules on distinct stimulator and/or effector cell populations.

Human glioma immunobiology in vitro: implications for immunogene therapy

OBJECTIVE

Human gliomas are known to be immunosuppressive. Recent reports have suggested novel strategies to overcome this immunosuppression, including immunogene therapy. We examined expression of 10 immunologically important molecules by human gliomas in vitro, and we discuss the implications for immunogene therapy.

METHODS

Early passage human glioma cultures and established human glioma cell lines were analyzed by flow cytometry for expression of Class I and II major histocompatibility complex (MHC), B7-2 (CD86), and Fas (CD95). Culture supernatants were assayed by enzyme-linked immunosorbent assay for interleukin (IL)-6, IL-10, IL-12, transforming growth factor beta2, prostaglandin E2, and granulocyte-macrophage colony-stimulating factor levels.

RESULTS

All cultures (16 of 16 samples) expressed Class I MHC and Fas, but few expressed Class II MHC (1 of 16 samples) or B7-2 (0 of 16 samples). Nearly all expressed high levels of IL-6 (19 of 21 samples; mean, 36.5 +/- 10.8 ng/10(6) cells/d) and prostaglandin E2 (21 of 21 samples; mean, 15.6 +/- 4.5 ng/10(6) cells/d) levels, and many expressed transforming growth factor beta2 (13 of 21 samples; mean, 8.6 +/- 3.7 ng/10(6) cells/d). Although several cultures (6 of 14 samples) expressed granulocyte-macrophage colony-stimulating factor, expression levels were very low (mean, 0.2 +/- 0.1 ng/10(6) cells/d). Few cultures (4 of 21 samples) expressed measurable IL-10, and none (0 of 22 samples) expressed IL-12.

CONCLUSION

Class I MHC and Fas expression suggests that human glioma cells may be susceptible to Class I MHC-dependent cytotoxic T cell recognition and Fas-mediated killing. Unfortunately, transforming growth factor beta2 and prostaglandin E2 probably impair T cell activation, and IL-6 may shift immunity to less effective humoral (T helper 2) responses. Proinflammatory gene expression (B7-2, granulocyte-macrophage colony-stimulating factor, and/or IL-12) is lacking. Together, these results suggest that modifying glioma cells via proinflammatory gene transfer or immunoinhibitory gene suppression might stimulate immune responses that are effective against unmodified tumors.

Nonlymphoid intraepidermal mononuclear cell collections (pseudo-Pautrier abscesses): a morphologic and immunophenotypical characterization

We evaluated the incidence, morphology, and immunophenotype of intraepidermal collections of mononuclear cells (ICMC) in a large number of inflammatory dermatosis and cutaneous lymphomas. ICMC appeared as small to large aggregates of cells, showing a morphology variable from monocytes to obvious dendritic cells, admixed with rare lymphocytes. ICMC were recognized in the epidermis or within hair follicle epithelium, and were either loosely or compactly arranged. ICMC were identified in 124 of 1,248 skin biopsies (9.9%) of inflammatory or lymphoid infiltrates, and were particularly frequent in spongiotic (43.4%) and in lichenoid dermatitis (10%), whereas they were rarely found in nonspecific superficial dermatitis (3.8%) and in psoriasis (4.7%). ICMC were also frequent in cutaneous T-cell lymphoma (13.3%), where they mimicked Pautrier abscesses. The ICMC forming cells showed a unique phenotype: the majority of them expressed CD1a and S-100, and lacked CD14, similar to mature Langerhans cells, but they were also strongly labeled by anti-CD11b, anti-CD36, and anti-CD68. Moreover, a subpopulation of them expressed CD83, an antigen that is usually absent on Langerhans cells. The occurrence of ICMC is a rather frequent, although hitherto poorly studied, phenomenon, occurring in several dermatosis, but particularly frequent in spongiosis-associated skin reactions. The cells within ICMC are represented by dendritic cells and dendritic cell precursors, whose phenotype indicates their derivation from circulating monocytes and differentiation into mature Langerhans cells.

Fas/Fas ligand-mediated apoptosis of murine Langerhans cells

Epidermal Langerhans cells (LC) are potent antigen-presenting cells (APC), that play a crucial role in initiating cutaneous immune responses. The Fas/Fas ligand pathway has been implicated as an important cellular pathway in the regulation of peripheral immunity. The morphologic, functional and phenotypic characteristics of LC are becoming well-characterized. However, the mechanisms involved in eliminating LC are poorly understood. In this report, we demonstrated that murine epidermal LC constitutively express the Fas antigen (CD95) and the expression was up-regulated by the addition of IFN-gamma in cultures. Interestingly, epidermal LC underwent apoptosis by the addition of both recombinant soluble Fas ligand (FasL) and IFN-gamma, but not by FasL alone. These results suggest that LC may acquire the susceptibility to Fas-mediated apoptosis through up-regulation of the Fas expression by IFN-gamma derived from activated T cells and that the elimination of LC may be important for preventing excess cutaneous inflammatory diseases.

Vaccination with mouse mammary adenocarcinoma cells coexpressing B7-1 (CD80) and B7-2 (CD86) discloses the dominant effect of B7-1 in the induction of antitumor immunity

Nonreplicating TS/A mammary adenocarcinoma cells expressing B7-2 (CD86) (TS/A-2) are more immunogenic than those expressing B7-1 (CD80) (TS/A-1), indicating that B7-1 and B7-2 display nonredundant costimulatory effects in inducing antitumor responses. Whereas transfection of B7-2 cDNA into TS/A-1 cells does not improve their immunogenicity, transfection of B7-1 cDNA into TS/A-2 cells (TS/A-2/1) decreases their immunogenicity in a manner that is directly related to the surface levels of B7-1. Ab blocking of B7-1 on TS/A-2/1 cells before their injection in vivo restores the higher immunogenicity characteristic of single B7-2 transfectants, indicating therefore that B7-1 actively modulates the B7-2-dependent costimulation. The expression of B7-1 also modifies quantitatively the balance of endogenous IFN-gamma and IL-4 induced in vivo by TS/A-2 vaccines. In fact, we find that vaccination with TS/A-2/1 cells results in the production of more IFN-gamma and less IL-4 than TS/A-2 vaccines, a pattern comparable to that induced by TS/A-1 cells. Thus, in the TS/A model of antitumor response, B7-1 modulates B7-2-dependent costimulatory effects in a dominant, noncompetitive way.

Contact Hypersensitivity Responses Following Ribavirin Treatment In Vivo Are Influenced by Type 1 Cytokine Polarization, Regulation of IL-10 Expression, and Costimulatory Signaling

We previously described the promotion of type 1 cytokine responses by the nucleoside analogue, ribavirin, in human T cells in vitro. In this study, we examined whether type 1 cytokine polarization by ribavirin in vivo could promote contact hypersensitivity (CHS) responses to dinitrofluorobenzene, a type 1 cytokine-mediated immune response. Unexpectedly, although type 1 cytokine responses were enhanced following ribavirin treatment in vitro and in vivo, the magnitude of CHS responses in BALB/c and C57BL/6 mice was influenced more by a second ribavirin-regulated pathway. The key regulatory molecule in this pathway was IL-10. Ribavirin-mediated suppression of IL-10 in BALB/c mice was associated with increased B7-2 expression and enhanced CHS responses, whereas enhanced IL-10 levels, following ribavirin administration, led to increased B7-1 expression and impaired CHS responses in C57BL/6 mice. The effect of ribavirin on the expression of B7 molecules and on CHS responses was neutralized by IL-10 administration in BALB/c and by anti-IL-10 Ab in C57BL/6. Thus, ribavirin controlled CHS responses directly through the modulation of IL-10 expression, and in vivo outcome was dictated by the preferential expression of either B7-1, an inappropriate costimulatory molecule in CHS, or B7-2, the predominant costimulatory molecule in CHS. Replacing dinitrofluorobenzene priming with IFN-α stimulation, we showed that the ribavirin-regulated pathway could function independent of Ag priming. Altogether, these data showed that, although ribavirin treatment induced a type 1 cytokine bias in contact allergen-primed BALB/c and C57BL/6 mice, in vivo CHS responses were dependent on ribavirin-mediated regulation of both IL-10 and preferential costimulatory signaling.

The interplay between T helper subset cytokines and IL-12 in directing human B lymphocyte differentiation

This study asks how T helper (TH) subset cytokines impact upon IL-12-directed change in B cells engaged in signaling via the B cell receptor and CD40, essential components in the initiation of T-dependent B cell responses. For B cells stimulated in this way, IL-12 promoted a distinct phenotype highlighted by the hyper-expression of CD38: the Th1 cytokine IFN-gamma reproduced the IL-12 effects while neutralizing antibody to IFN-gamma reversed IL-12-dependent change. The divergent pathway of differentiation promoted by the Th2 cytokine IL-4 (characterized by hyper-induction of CD23) was left unchecked by IL-12. IL-10 was found to dampen IL-12 actions by suppressing IL-12-dependent IFN-gamma production but failed to perturb the effects of exogenous IFN-gamma. Thus, IL-12--by invoking autocrine IFN-gamma production--promotes phenotypic deviation in B cells engaging T-dependent signals. The reversal of such Th1 driving of B cells by IL-10 only when the source of IFN-gamma is endogenous and the inability of IL-12 to impact upon IL-4-directed differentiation suggest a progressive and hierarchical commitment of B cells to polarization during a developing T-dependent response dominated at the level of the Th cell rather than that of the dendritic cell.

Evidence That Langerhans Cells in Adult Pulmonary Langerhans Cell Histiocytosis Are Mature Dendritic Cells: Importance of the Cytokine Microenvironment

Because Langerhans cells (LC) in peripheral tissues are generally “immature” cells with poor lymphostimulatory activity, the contribution of immune responses initiated by LC to the pathogenesis of pulmonary LC histiocytosis (LCH) has been uncertain. In this study we demonstrate that LC accumulating in LCH granulomas are phenotypically similar to mature lymphostimulatory dendritic cells present in lymphoid organs. LC in LCH granulomas intensely expressed B7-1 and B7-2 molecules, whereas normal pulmonary LC and LC accumulating in other pathologic lung disorders did not express these costimulatory molecules. The presence of B7+ LC in LCH granulomas was associated with the expression in these lesions, but not at other sites in the lung, of a unique profile of cytokines (presence of GM-CSF, TNF-α, and IL-1β and the absence of IL-10) that is known to promote the in vitro differentiation of LC into cells expressing a lymphostimulatory phenotype. Finally, LCH granulomas were the only site where CD154-positive T cells could be identified in close contact with LC intensely expressing CD40 Ags. Taken together, these results strongly support the idea that an abnormal immune response initiated by LC may participate in the pathogenesis of pulmonary LCH, and suggest that therapeutic strategies aimed at modifying the lymphostimulatory phenotype of LC may be useful in the treatment of this disorder.

Down-regulation of Th2 responses by Brucella abortus, a strong Th1 stimulus, correlates with alterations in the B7.2-CD28 pathway

Down-regulation of the Th2-like response induced by ovalbumin-alum (OVA/alum) immunization by heat-killed Brucella abortus was not reversed by anti-IL-12 antibody treatment or in gamma interferon (IFN-gamma) knockout mice, suggesting that induction of Th1 cytokines was not the only mechanism involved in the B. abortus-mediated inhibition of the Th2 response to OVA/alum. The focus of this study was to determine whether an alternative pathway involves alteration in expression of costimulatory molecules. First we show that the Th2-like response to OVA/alum is dependent on B7.2 interaction with ligand since it can be abrogated by anti-B7.2 treatment. Expression of costimulatory molecules was then studied in mice immunized with OVA/alum in the absence or presence of B. abortus. B7.2, but not B7.1, was up-regulated on mouse non-T and T cells following immunization with B. abortus. Surprisingly, B. abortus induced down-regulation of CD28 and up-regulation of B7.2 on murine CD4(+) and CD8(+) T cells. These effects on T cells were maximal for CD28 and B7.2 at 40 to 48 h and were not dependent on interleukin-12 (IL-12) or IFN-gamma. On the basis of these results, we propose that the IL-12/IFN-gamma-independent inhibition of Th2 responses to OVA/alum is secondary to the effects of B. abortus on expression of costimulatory molecules on T cells. We suggest that down-regulation of CD28 following activation inhibits subsequent differentiation of Th0 into Th2 cells. In addition, decreased expression of CD28 and increased expression of B7.2 on T cells would favor B7.2 interaction with CTLA-4 on T cells, and this could provide a negative signal to developing Th2 cells.

Fas/Fas ligand-mediated elimination of antigen-bearing Langerhans cells in draining lymph nodes

Epidermal Langerhans cells (LC) are potent antigen-presenting cells (APC) that play a crucial part in initiating cutaneous immune responses. Although functional roles of LC as APC in the draining lymph node have been well investigated, little is known about the fate of LC after the antigen presentation to T cells. In this report, we demonstrate that antigen-bearing LC that migrated into the draining lymph nodes and were identified as fluorescent cells after skin painting with fluorescein isothiocyanate also expressed the Fas antigen. Clearance of the antigen-bearing LC was significantly delayed and the ratio of dead cells was reduced in Fas-deficient lpr and Fas ligand (FasL)-deficient gld mice at 2 days after skin painting, suggesting the involvement of a Fas/FasL-mediated pathway in the elimination of antigen-bearing LC in draining lymph nodes. These results suggest that a substantial population of LC after antigen presentation may undergo Fas/FasL-mediated apoptosis and that the elimination of active APC may be important for preventing excess immune responses.

Dendritic cells as regulators of immune reactivity: implications for transplantation

Dendritic cells are now regarded not only as the initiators but also as regulators of immune responses. They are potentially powerful tools for the therapeutic manipulation of immune reactivity in cancer, infectious disease, and allograft rejection. We provide a brief overview of the properties of dendritic cells, with emphasis on recently acquired information, then focus attention on their capacity to modulate immune reactivity, and its relevance to transplantation.

Differential expression and modulation of costimulatory molecules CD80 and CD86 on monocytes from patients with systemic lupus erythematosus

Patients with systemic lupus erythematosus (SLE) were recently shown to be defective in costimulatory molecule CD80 (B7-1) expression on antigen-presenting cells. This study was undertaken to further investigate the expression and cytokine regulation of both CD80 and CD86 (B7-2) on monocytes from patients with SLE. Freshly isolated and in vitro cytokine-stimulated peripheral blood mononuclear cells from 13 patients with SLE and 10 healthy subjects were analysed, cytometrically with dual-fluorescence staining, to detect expression of CD80 and CD86 in the CD14+ monocyte population. The results showed that, as in normal individuals, an overwhelming majority (95.62+/-3.54%) of monocytes from patients with SLE expressed the CD86 molecule, but only a few monocytes (5.54+/-4.36%) had detectable CD80 expression. The effects of interleukin-10 (IL-10) on the expression of CD80 and CD86 on monocytes from patients with SLE and normal controls were similar. IL-10 down-regulated the expression of CD86 while it slightly enhanced that of CD80. Interferon-gamma (IFN-gamma) increased both CD80 and CD86 expression on monocytes from both SLE patients and normal groups, albeit less significantly in the former than in the latter, i.e. CD80: 142.84+/-65.99% versus 226.08+/-78.90%, P<0.05; and CD86: 72.55+/-74.23% versus 153.99+/-94.14%, P<0.05, when expressed as percentage modulation. Granulocyte-macrophage colony-stimulating factor (GM-CSF) showed a capacity for up-regulation of CD80 and CD86 expression on monocytes, of a magnitude that was similar both in patients with SLE and in normal subjects. We concluded that CD80 and CD86 were differentially expressed and modulated on monocytes and the defective IFN-gamma-induced up-regulation of CD80 and CD86 expression on SLE monocytes might be a factor in the pathogenesis of SLE.

Distinct roles for B7 costimulation in contact hypersensitivity and humoral immune responses to epicutaneous antigen

Productive interactions between B7-1 and B7-2 costimulatory molecules on dendritic cells (DC) and CD28 on T cells are thought to be critical for successful antigen presentation. Epicutaneous application of haptens induces both contact hypersensitivity (CHS), an inflammatory cutaneous response mediated by CD8+ T cells, and an anti-hapten antibody response mediated by CD4+ helper T cells. The role of B7 costimulation in the immune response to oxazolone (Ox) was analyzed using mice lacking either B7-1 (B7-1-/-), B7-2 (B7-2-/-), or both (Db-/-) of these costimulatory molecules. The absence of both B7-1 and B7-2 results in diminished CHS. This inhibition is largely overcome at higher hapten sensitizing doses indicating the presence of compensatory pathways. In contrast, anti-Ox IgG1 and IgG2a responses were not detected in the absence of both B7-1 and B7-2, even at high sensitizing doses, indicating an obligatory role of B7 costimulation in IgG class switching. B7-1 and B7-2 have overlapping functions in both CHS responses and anti-hapten response. B7-2-/- mice demonstrated a modestly reduced CHS response only at very low doses of Ox (0.05%), but responded normally at higher Ox doses, and B7-1-/- mice had CHS responses indistinguishable from those of wild-type mice. Similarly, anti-Ox IgG responses were comparable in wild-type, B7-1-/- and B7-2-/- mice. Taken together, these studies reveal distinct roles for B7 costimulation in response to epicutaneous antigens with an obligatory role for IgG class switching and an important, but nonessential role for CHS responses.

Human Muscle Cells Express a Functional Costimulatory Molecule Distinct from B7.1 (CD80) and B7.2 (CD86) In Vitro and in Inflammatory Lesions

The B7 family of costimulatory molecules likely includes members distinct from B7.1 (CD80) and B7.2 (CD86). After stimulation with IFN-γ or TNF-α, human myoblasts selectively express BB-1, but not B7.1 or B7.2. BB-1 is detected by anti-BB-1, a mAb cross-reacting with B7.1 (but not B7.2) and an as yet undefined costimulatory molecule. The absence of B7.1 and B7.2 in BB-1-positive myoblasts was confirmed by RT-PCR. The molecule detected by anti-BB-1 is functional, because anti-BB-1 mAb and CTLA4Ig (but not anti-B7.1- or anti-B7.2-specific mAbs) completely inhibit Ag presentation by cytokine-induced myoblasts to HLA-DR-matched Ag-specific CD4+ T cell lines. Stimulation of myoblasts with IL-4 induces B7.1 and B7.2, as well as BB-1, but with different time kinetics. Stimulation of CD40-positive myoblasts with anti-CD40 mAb selectively induces BB-1, whereas stimulation with CD40L-transfected mouse L cells induces BB-1 and B7.1, with different kinetics. To assess whether BB-1 is expressed in muscle tissue, we investigated 23 muscle biopsy specimens from patients with polymyositis, dermatomyositis, inclusion body myositis, Duchenne muscular dystrophy, and nonmyopathic controls by immunohistochemistry and confocal laser microscopy. We found that, in all inflammatory myopathy cases, but not in normal muscle, many muscle fibers strongly react with anti-BB-1. In contrast, muscle fibers did not react with B7.1- or B7.2-monospecific mAbs in any of the pathologic specimens or in normal muscle. Our results demonstrate that human muscle cells can be induced to selectively express BB-1, a functional costimulatory molecule distinct from B7.1 and B7.2. This molecule may play an important role in the immunobiology of muscle.

IL-12 promotes the accessory cell function of epidermal Langerhans cells

The objective of this study was to investigate the effects of cytokines regulating cutaneous immune responses, on the accessory cell function of epidermal cells (EC). EC were treated with various cytokines, and the accessory cell function of the cytokine-pretreated EC was examined by the allogeneic mixed epidermal cell-lymphocyte reaction (MECLR). Among the cytokines examined, IFN-gamma- and IL-12-pretreated EC augmented IFN-gamma production in the MECLR, while none of the other cytokines was effective. However, the cytokine-pretreated EC did neither affect T cell proliferation nor IL-4 production in the MECLR. Next we attempted to analyze the mechanisms by which IL-12-pretreated EC increase IFN-gamma production in the MECLR. Endogenous IFN-gamma produced during the IL-12 pretreatment of EC was found to play only a minor role in modulating the function of EC. The expression of MHC class II, CD80 and CD86 on EC was not affected by IL-12. On the other hand, soluble mediators that induce IFN-gamma production during the MECLR containing IL-12-pretreated EC were identified as endogenously produced IL-12 (the major mediator) and IL-18 (the minor mediator). Furthermore, the results of depletion experiments indicate that IL-12 promotes the accessory cell function of Langerhans cells to responder T cells in inducing IFN-gamma production in the MECLR.

Effects of ultraviolet B radiation on human Langerhans cells: functional alteration of CD86 upregulation and induction of apoptotic cell death

We have recently reported that in vitro low dose of ultraviolet B radiation (UVB, 100-200 J per m2) directly impaired the antigen-presenting function of human Langerhans cells. In this study, we analyzed the effect of UVB irradiation on the Langerhans cells expression of several accessory molecules, namely CD54, CD80, and CD86. Langerhans cells phenotype was determined either immediately after UVB exposure (100 J per m2) or after a 2 d culture. No modification in cell surface antigen levels was observed immediately after irradiation. Prior UVB exposure did not modify the levels of CD80 at the Langerhans cells surface after a 2 d culture. In contrast, CD54 and, above all, CD86 expression were significantly decreased. Addition of exogenous anti-CD28 monoclonal antibodies partly restored the allostimulatory property of irradiated Langerhans cells in mixed epidermal cell-lymphocyte reaction, demonstrating that impairment of CD86 upregulation contributes to the UVB-induced immunosuppressive effect. Furthermore, we found that UVB irradiation at 200 J per m2 significantly reduced the number of viable Langerhans cells after 2 d of culture. UVB-induced cytotoxicity was due to apoptotic cell death, as demonstrated by typical morphologic alterations and by DNA fragmentation yielding a classical ladder pattern on gel electrophoresis. Interestingly, interaction of Langerhans cells with CD40-ligand transfected L cells improved the viability of irradiated Langerhans cells, counteracted the inhibition of CD86 expression, and efficiently reduced the number of apoptotic cells after a 2 d culture. Collectively, these results demonstrate that in vitro UVB exposure affects Langerhans cells via at least two distinct pathways: (i) decreased CD86 costimulatory molecule upregulation; and (ii) induction of Langerhans cells apoptosis, a phenomenon partly prevented by CD40 triggering.

In human skin, UVB initiates early induction of IL-10 over IL-12 preferentially in the expanding dermal monocytic/macrophagic population

In contrast to Langerhans cells, which make interleukin (IL)-12, differentiated macrophages that infiltrate the epidermis 72 h after ultraviolet B (UV) irradiation potently produce IL-10 mRNA and secrete IL-10 protein. We asked whether differentiated UV macrophages in the epidermis acquired their activated, IL-10hi status as a result of entering the epidermis or as a result of encountering UV-induced changes in the dermal microenvironment. In this study, sequential section immunostaining directly showed dynamic and reciprocal changes of infiltrating CD11b+ macrophages and CD1a+ Langerhans cell loss in human epidermis and dermis after in vivo UV exposure in relation to the microanatomic localization of newly appearing dermal cells that stain for IL-10 mRNA by in situ hybridization. Using quantitative reverse transcriptase polymerase chain reaction on purified dermal cell subsets, the first significant rise in IL-10 mRNA occurred 6 h after UV in the dermal CD11b+ (CD1-, 3-, 24-, 56-) monocytic/macrophagic population. Significant induction of IL-10 mRNA 24 h post-UV was limited to the CD11b+ CD1- subset (p = 0.006). The fold increase of IL-10 mRNA relative to 0 h by the CD11b+ dermal monocytic/macrophagic population peaked at 24-48 h and tapered thereafter. Intense IL-10 production by macrophages in the epidermis appeared to follow dermal changes, with maximum production at 72 h, indicating migration/activation of this population from the dermis, and the remainder of dermal cells, depleted of monocyte/macrophages and Langerhans cell-like antigen-presenting cells, showed no increase in IL-10 at any time point post-UV. IL-10 protein-producing CD11b+ macrophages in the dermis were also documented by flow cytometry. IL-12 mRNA was differentially regulated from IL-10 after UV, in that IL-12 was consistently downregulated in the CD11b+ monocytic/macrophagic population (p < 0.0002). Taken together, monocytic/macrophagic cells with high IL-10 and low IL-12 expression initially appear in the dermis as early as 6 h, and then appear in the epidermis, implicating the dermis as the primary site of activation/signaling for IL-10 upregulation in cutaneous antigen-presenting cells.

CD86 (B7-2) antigen on B cells from atopic patients shows selective, antigen-specific upregulation

To determine whether B7 signals are associated with atopic responses in man, we assayed CD80 and CD86 expression on B cells and monocytes from atopic patients and controls. Peripheral blood mononuclear cells from 10 patients with perennial allergic rhinitis and from 10 normal subjects were cultured in the presence or absence of house-dust-mite antigen, and B cells and monocytes were assayed for expression of CD80 and CD86 by flow cytometry. CD86 on B cells was significantly and selectively upregulated in all atopic subjects, but not in normal subjects, whereas CD80 expression was not altered in B cells from the atopic subjects or controls. In contrast, both CD80 and CD86 were upregulated in monocytes from the atopic subjects as well as the controls. However, CD86 upregulation was significantly higher in the atopic subjects than in controls. Our results seem to suggest that selective upregulation of CD86 on B cells by a challenging antigen may play a critical role in the development of Th2 cells in patients with atopic disease.

Increased expression of the novel molecule OX-2 is involved in prolongation of murine renal allograft survival

BACKGROUND

Portal venous (p.v.) peritransplant immunization with dendritic cells from bone marrow cultures, along with cyclosporine (10 mg/kg), produces antigen-specific increased renal allograft survival compared with recipients receiving intravenous (i.v.) immunization. Increased survival is associated with altered cytokine production from recipient T cells restimulated with donor antigen. We used a suppressive subtractive hybridization approach to explore a role in the regulation of transplant rejection for other genes differentially expressed after p.v. immunization.

METHODS

Subtractive hybridization was performed using tissue from p.v. and i.v. immunized mice and a novel polymerase chain reaction-based approach. A gene-bank search was used to identify the source of the differentially expressed cDNAs. One product, the mouse homologue of rat OX-2, was further analyzed using Western gels and FACS analysis of dendritic cells (NLDC145+) isolated from p.v.-immunized mice.

RESULTS

Eighty cDNA clones were obtained by suppressive subtractive hybridization. Differential expression was confirmed in Northern RNA blots. One clone showed sequence homology to a gene encoding a molecule on rat dendritic cells (MRC OX-2), with homology to genes encoding the costimulatory molecules CD80 (B7-1) and CD86 (B7-2). In p.v.-immunized mice, a monoclonal antibody to the rat OX-2 molecule identified, by Western blot analysis, increased expression of a molecule with molecular weight (43 kDa) analogous to rat MRC-OX-2; labels (by FACS analysis) indentified increased numbers of a population of cells staining with NLDC145; and blocks indentified increased graft survival.

CONCLUSION

Our data suggest that OX-2 is functionally important in the increased graft survival seen in p.v.-immunized mice receiving renal allografts.

T helper 1 (Th1) and Th2 characteristics start to develop during T cell priming and are associated with an immediate ability to induce immunoglobulin class switching

The respective production of specific immunoglobulin (Ig)G2a or IgG1 within 5 d of primary immunization with Swiss type mouse mammary tumor virus [MMTV(SW)] or haptenated protein provides a model for the development of T helper 1 (Th1) and Th2 responses. The antibody-producing cells arise from cognate T cell B cell interaction, revealed by the respective induction of Cgamma2a and Cgamma1 switch transcript production, on the third day after immunization. T cell proliferation and upregulation of mRNA for interferon gamma in response to MMTV(SW) and interleukin 4 in response to haptenated protein also starts during this day. It follows that there is minimal delay in these responses between T cell priming and the onset of cognate interaction between T and B cells leading to class switching and exponential growth. The Th1 or Th2 profile is at least partially established at the time of the first cognate T cell interaction with B cells in the T zone. The addition of killed Bordetella pertussis to the hapten-protein induces nonhapten-specific IgG2a and IgG1 plasma cells, whereas the anti-hapten response continues to be IgG1 dominated. This indicates that a Th2 response to hapten-protein can proceed in a node where there is substantial Th1 activity.

Epicutaneous sensitization with protein antigen induces localized allergic dermatitis and hyperresponsiveness to methacholine after single exposure to aerosolized antigen in mice

Our understanding of the pathogenesis of atopic dermatitis (AD) and its relationship to asthma remains incomplete. Herein, we describe a murine model of epicutaneous (EC) sensitization to the protein allergen, chicken egg albumin, ovalbumin (OVA), which results in a rise in total and OVA-specific serum IgE and leads to the development of a dermatitis characterized by infiltration of CD3(+) T cells, eosinophils, and neutrophils and by local expression of mRNA for the cytokines IL-4, IL-5, and interferon-gamma. A single exposure of the EC sensitized mice to aerosolized OVA induced eosinophilia in the bronchoalveolar lavage fluid and airway hyperresponsiveness to intravenous methacholine as assessed by measurement of pulmonary dynamic compliance (Cdyn). These results suggest a possible role for EC exposure to antigen in atopic dermatitis and in the development of allergic asthma.

Blockade of B7-2, not B7-1, inhibits purified protein derivative-primed T-lymphocyte responses but fails to influence the proportion of Th1 versus Th2 subsets

The ability to select for a cell-mediated response rather than antibody production following infection with intracellular mycobacteria, would be an advantage in preventing the occurrence of disease. Recent work suggests that the two members of the B7 family of costimulatory molecules, B7-1 and B7-2, may differentially influence the nature of primary immune responses but little is known of their role in this capacity in secondary responses. We have used an in vitro model to investigate whether blocking B7-1 and B7-2 affects changes in the cytokine profiles of Th lymphocytes previously primed to purified protein derivative (PPD) from Mycobacterium bovis. In C57BL/6 and BALB/c mice we found that the proliferative responses of a component of recently activated T lymphocytes, and those returning to the resting state, were inhibited by B7-2 blockade. B7-1 blockade had no distinguishable effect. However, in cultures containing anti-B7-2 antibody, the production of both interferon-gamma (IFN-gamma) and interleukin-4 (IL-4), indicative of cell-mediated and antibody responses, respectively, were reduced. This suggests that intervention in a recall response to mycobacterial antigen by blocking B7-1 or B7-2 molecules, is unlikely to alter the nature of the immune response.

Maturation of dendritic cells induced by cytokines and haptens

Recently, elucidation has progressed on a crucial role played by dendritic cells (DCs) in the induction of primary antigen-specific immune reactions. Although mature DCs exhibit potent antigen presenting function, DCs are scattered in nonlymphoid organs throughout the body as immature cells that have only minimum antigen presenting function. When they are stimulated to maturate, they increase their expression of class II major histocompatibility (MHC) antigen and several co-stimulatory molecules, resulting in the augmentation of antigen presenting function. Furthermore, these maturated DCs move to the T-dependent areas of secondary lymphoid organs to sensitize naive T cells for these antigens. Therefore, it is important to understand the mechanism to induce the maturation of DCs. Recent progress in the study of DC biology depicts various factors, such as cytokines, bacterial products and haptens, which are responsible for DC maturation. In this paper, the mechanism of DC maturation induced by cytokines and chemicals is described.

Interleukin-10 promotes activation-induced cell death of SLE lymphocytes mediated by Fas ligand

Immune function in SLE is paradoxically characterized by active T cell help for autoantibody production, along with impaired T cell proliferative and cytokine responses in vitro. To reconcile these observations, we investigated the possibility that the accelerated spontaneous cell death of SLE lymphocytes in vitro is caused by an activation-induced cell death process initiated in vivo. 27 SLE patients, three patients with systemic vasculitis, seven patients with arthritis, and 14 healthy subjects were studied. Patients with clinically active SLE or systemic vasculitis had accelerated spontaneous death of PBMC with features of apoptosis at day 5 of culture. A prominent role for IL-10 in the induction of apoptosis was observed, as neutralizing anti-IL-10 mAb markedly reduced cell death in the active SLE patients by 50%, from 22.3 +/- 5.2% to 11.2 +/- 2.8%, and the addition of IL-10 decreased viability in the active SLE group, but not in the control group, by 38%. In addition, apoptosis was shown to be actively induced through the Fas pathway. The potential clinical relevance of T cell apoptosis in active SLE is supported by the correlation of increased apoptosis and IL-10 levels in vitro with low lymphocyte counts in vivo. We conclude that the spontaneous cell death observed in vitro in lymphocytes from patients with SLE and other systemic autoimmune disorders results from in vivo T cell activation, is actively induced by IL-10 and Fas ligand, and reflects pathophysiologically important events in vivo. Activation-induced cell death in vivo provides a pathogenic link between the aberrant T helper cell activation and impaired T cell function that are characteristic features of the immune system of patients with SLE.

Neonatal activation of CD28 signaling overcomes T cell anergy and prevents autoimmune diabetes by an IL-4-dependent mechanism

Optimal T cell responsiveness requires signaling through the T cell receptor (TCR) and CD28 costimulatory receptors. Previously, we showed that T cells from autoimmune nonobese diabetic (NOD) mice display proliferative hyporesponsiveness to TCR stimulation, which may be causal to the development of insulin-dependent diabetes mellitus (IDDM). Here, we demonstrate that anti-CD28 mAb stimulation restores complete NOD T cell proliferative responsiveness by augmentation of IL-4 production. Whereas neonatal treatment of NOD mice with anti-CD28 beginning at 2 wk of age inhibits destructive insulitis and protects against IDDM by enhancement of IL-4 production by islet-infiltrating T cells, administration of anti-CD28 beginning at 5-6 wk of age does not prevent IDDM. Simultaneous anti-IL-4 treatment abrogates the preventative effect of anti-CD28 treatment. Thus, neonatal CD28 costimulation during 2-4 wk of age is required to prevent IDDM, and is mediated by the generation of a Th2 cell-enriched nondestructive environment in the pancreatic islets of treated NOD mice. Our data support the hypothesis that a CD28 signal is requisite for activation of IL-4-producing cells and protection from IDDM.