Secrets and lies of host-microbial interactions: MHC restriction and trans-regulation of T cell trafficking conceal the role of microbial agents on the edge between health and multifactorial/complex diseases

Here we critically discuss data supporting the view that microbial agents (pathogens, pathobionts or commensals alike) play a relevant role in the pathogenesis of multifactorial diseases, but their role is concealed by the rules presiding over T cell antigen recognition and trafficking. These rules make it difficult to associate univocally infectious agents to diseases' pathogenesis using the paradigm developed for canonical infectious diseases. (Cross-)recognition of a variable repertoire of epitopes leads to the possibility that distinct infectious agents can determine the same disease(s). There can be the need for sequential infection/colonization by two or more microorganisms to develop a given disease. Altered spreading of infectious agents can determine an unwanted activation of T cells towards a pro-inflammatory and trafficking phenotype, due to differences in the local microenvironment. Finally, trans-regulation of T cell trafficking allows infectious agents unrelated to the specificity of T cell to modify their homing to target organs, thereby driving flares of disease. The relevant role of microbial agents in largely prevalent diseases provides a conceptual basis for the evaluation of more specific therapeutic approaches, targeted to prevent (vaccine) or cure (antibiotics and/or Biologic Response Modifiers) multifactorial diseases.

Study of the effects of Lemna minor extracts on human immune cell populations

OBJECTIVE

Lemna minor is a plant with a huge repertoire of secondary metabolites. The literature indicates that extracts of Lemna minor have antioxidant, antiradical, immunomodulatory and anti-inflammatory properties. The objective of the present study was to find a suitable technique to extract active compounds from this plant and verify whether these extracts have immunomodulatory activity.

MATERIALS AND METHODS

We grew L. minor on a standard medium with Gamborg B5 and vitamins. We extracted compounds from the plant by maceration and decoction. The phytochemical profile of the extracts was characterized by chromatography, spectrophotometry, and spectroscopy. The extracts were tested on cultures of mononuclear cells from four human subjects. These cells were pulsed with carboxyfluorescein succinimidyl ester, grown in triplicate in standard culture medium without (control) and with increasing concentrations of Lemna extracts. Flow cytometry was used to evaluate cell death and proliferation of the total mononuclear cell population and of CD4+, CD8+, B cell and monocyte populations.

RESULTS

The Lemna extracts were not cytotoxic and did not cause cell necrosis or apoptosis in immune cells. At low concentrations, they induced very limited proliferation of CD4+ cells within 48 hours. At high concentrations, they induced proliferation of CD8+ cells and B lymphocytes within 48 hours.

CONCLUSIONS

Unfortunately, we failed to confirm any immunomodulatory activity of Lemna extracts. Growth and death rates of human immune cells were not significantly affected by adding Lemna extracts to the culture medium.

House dust mite allergy and shrimp allergy: a complex interaction

Summary

Background and Objective. Sensitization and allergy to shrimp among Italian house dust mite allergic patients are not well defined and were investigated in a large multicenter study. Methods. Shrimp sensitization and allergy were assessed in 526 house dust mite (HDM)-allergic patients submitted to the detection of IgE to Der p 10 and 100 atopic control not sensitized to HDM. Results. Shrimp allergy occurred in 9% of patients (vs 0% of 100 atopic controls not sensitized to HDM; p minor 0.001). Shrimp-allergic patients were less frequently hypersensitive to airborne allergens other than HDM than crustacean-tolerant subjects (35% vs 58.8%; p minor 0.005). Only 51% of tropomyosin-sensitized patients had shrimp allergy, and these showed significantly higher Der p 10 IgE levels than shrimp-tolerant ones (mean 22.2 KU/l vs 6.2 KU/l; p minor 0.05). Altogether 53% of shrimp-allergic patients did not react against tropomyosin. Conclusions. Shrimp allergy seems to occur uniquely in association with hypersensitivity to HDM allergens and tropomyosin is the main shrimp allergen but not a major one, at least in Italy. Along with tropomyosin-specific IgE levels, monosensitization to HDM seems to represent a risk factor for the development of shrimp allergy among HDM allergic patients.

TLR2: A Crossroads between Infections and Autoimmunity?

Environment has both pathogenic and protective roles in the determination of autoimmune disease development, possibly through infectious agents. TLR2 has the capability to recognize the widest range of PAMPs, and it is important for the recognition of mycobacteria and gram-positive bacteria. Here we review recent information showing that TLR2 ligands, its signaling machinery and the effects of its engagement on T cell polarization and differentiation, all play a decisive role in experimental models of autoimmunity. Thus, we propose that engagement of TLR2 is an important crossroads between encounter with bacteria and development of self-reactive diseases.

Skewed T-cell receptor repertoire: more than a marker of malignancy, a tool to dissect the immunopathology of inflammatory diseases

The highly diverse heterodimeric surface T cell receptor (TCR) gives the T lymphocyte its specificity for MHC-bound peptides needed to initiate antigen-recognition. In normal peripheral blood, spleen and lymph nodes, the TCR repertoire of the T lymphocytes is usually polyclonal. However, in malignancies such as leukemias, as well as in lymphoproliferative diseases of mature T cells, the TCR is a reflection of the clonality of the malignant cells and is therefore monoclonal. Several clinical conditions (mainly solid tumors and autoimmune diseases) have been described where the TCR repertoire is restricted. The ability to demonstrate clonal TCR usage provides a useful tool to dissect the immunopathology of inflammatory diseases. In this review we discuss these findings and propose to sub-divide diseases with restricted TCR repertoire into a group of conditions in which there is a known TCR ligand, as opposed to diseases in which the restricted TCR repertoire is the result of impaired T-cell development. This classification sheds light on the pathogenesis of several inflammatory diseases.

Immune response at birth, long-term immune memory and 2 years follow-up after in-utero anti-HBV DNA immunization

Infections occurring at the end of pregnancy, during birth or by breastfeeding are responsible for the high toll of death among first-week infants. In-utero DNA immunization has demonstrated the effectiveness in inducing specific immunity in newborns. A major contribution to infant immunization would be achieved if a vaccine proved able to be protective as early as at the birth, preventing the typical 'first-week infections'. To establish its potential for use in humans, in-utero DNA vaccination efficiency has to be evaluated for short- and long-term safety, protection at delivery, efficacy of boosts in adults and effective window/s for modulation of immune response during pregnancy, in an animal model suitable with human development. Here we show that a single intramuscular in-utero anti-HBV DNA immunization at two-thirds of pig gestation produces, at birth, antibody titers considered protective in humans. The boost of antibody titers in every animal following recall at 4 and 10 months demonstrates the establishment of immune memory. The safety of in-utero fetus manipulation is guaranteed by short-term (no fetus loss, lack of local alterations, at-term spontaneous delivery, breastfeeding) and long-term (2 years) monitoring. Treatment of fetuses closer to delivery results in immune ignorance without induction of tolerance. This result highlights the repercussion of selecting the appropriate time point when this approach is used to deliver therapeutic genes. All these findings illustrate the relevance of naked DNA-based vaccination technology in therapeutic efforts aimed to prevent the high toll of death among first-week infants.

Molecular characterization of the T cell repertoire using immunoscope analysis and its possible implementation in clinical practice

T lymphocytes play a central role in the pathogenesis of a large number of human conditions including autoimmunity and graft rejection. Although T cells are key players in mounting immune responses, the assessment of T cell repertoires has yet to find an important role in clinical decision making. In this review, we discuss the "immunoscope" technique and its potential diagnostic role in a variety of clinical scenarios. This is an RT-PCR based approach that subdivides a bulk T cell population (i. e. from blood, lymph, spleen, or tissue) into approximately 2800 groups based upon rearranged variable beta (Vbeta)/joining beta (Jbeta) gene segments and the resulting length of the T cell receptor's (TCR's) third complementarity determining region (CDR-3). This extensive subdivision, or focusing, allows clonal expansions to be directly observed. Such a fine-tuned analysis has revealed previously unappreciated aspects of the T cell repertoire. For instance, an antigen-specific immune response can be divided into both public and non-public components. The non-public repertoire contains the majority of the expanding T cells which are unique to the individual (private), or shared by only some (semi-private), while "public" T cells can be found responding to the antigenic determinant in every individual. Although they are often a minority of the response, the public T cell repertoire seems to play a more important role in defining, as well as driving, the overall immune phenotype in the animal. Immunoscope analysis has identified public and non-public responses in human pathologies, such as multiple sclerosis. The ability to characterize the driver T cells dictating the state of immunity/autoimmunity in individual patients will be an important step towards understanding autoimmunity and designing effective treatment for a variety of conditions including rheumatoid arthritis and multiple sclerosis. We review the current literature involving public and non-public repertoires and discuss the prospect that immunoscope analysis may play a central role in the study and perhaps the management of human autoimmune diseases, and cancer.

Antibodies elicited by naked DNA vaccination against the complementary-determining region 3 hypervariable region of immunoglobulin heavy chain idiotypic determinants of B-lymphoproliferative disorders specifically react with patients' tumor cells

Several reports have suggested that the mechanism of protection induced by antiidiotypic vaccination against low-grade lymphoproliferative disorders is likely to be antibody mediated. Here we test the hypothesis that DNA vaccination with the short peptide encompassing the complementary-determining region 3 hypervariable region of immunoglobulin heavy chain (VH-CDR3) may elicit a specific antibody immune response able to recognize the native antigens in the form required for therapy. As a test system, we used the VH-CDR3 sequences derived from two patients with non-Hodgkin's B lymphomas (PA, AS) and one patient with hairy cell leukemia (BA) to immunize outbred Swiss mice. This experimental model could mimic a clinical setting in which different patients present distinct HLA haplotypes. Individual tumor-specific VH-CDR3 sequences were amplified by a two-step procedure and directly cloned into multigenic plasmid vectors (pRC100 and derived) with and without mouse interleukin 2 (mIL-2). Each tumor-specific sequence was characterized by sequencing. Female Swiss mice were vaccinated i.m. with plasmids expressing the tumor-specific VH-CDR3 sequence alone (pRC101-PA), mIL-2 plus the VH-CDR3 sequence (pRC111-PA), or a different unrelated antigen (NS3 of hepatitis C virus; pRC112), the sole mIL-2 (pRC110), and the empty plasmid (pRC100). Boost injections were performed at 3 and 16 weeks from the first vaccination, and sera were drawn before each vaccination and at 6, 9, and 19 weeks. Induction of anti-VH-CDR3s antibodies in the sera and their ability to recognize native antigens on patients' tumor cells were evaluated by FACS analysis. Up to 56% (n = 25) of mice vaccinated with pRC111-PA plasmid and 20% (n = 15) of mice vaccinated with pRC101-PA developed a specific immune response that was maintained throughout 19 weeks of observation in 40% of pRC111-PA-vaccinated mice. No response was detected in sera obtained from mice vaccinated with the other plasmids (n = 45). pRC111-PA injection s.c. was less effective (13%, n = 15) than i.m. injection (53%, n = 15). Indeed, we demonstrated that antibodies elicited by naked DNA vaccination against three different patient-derived VH-CDR3 peptides (pRC111-PA or BA or AS) readily reacted with binding epitopes on the idiotypic proteins expressed on the surface of tumor cells derived from each patient; 60, 40, and 40% of, respectively, PA-, BA-, and AS-vaccinated mice developed specific antibodies. No cross-reactivity was detected among the three different CDR3s against tumor cells derived from the other two patients. The outbred mouse strategy confirmed the significant matching potential of three different VH-CDR3 peptides to be efficaciously presented through different MHCs. We conclude that individual VH-CDR3 DNA vaccination can result in a potentially effective specific immune response against non-Hodgkin's B lymphoma cells by a rapid and low-cost therapeutic approach.

The level of manganese superoxide dismutase content is an independent prognostic factor for glioblastoma. Biological mechanisms and clinical implications

We address the issue of the role of manganese superoxide dismutase in tumorigenesis by studying a relatively homogeneous group of tumours for the correlation between amount of this anti-oxidant enzyme and prognosis. The clinical outcome of 30 patients affected by glioblastomas whose manganese superoxide dismutase content had been established at the time of first diagnosis is compared. When the survival of patients is stratified according to manganese superoxide dismutase level in the tumour, a link of these levels and prognosis can be observed. Patients with high levels of manganese superoxide dismutase show a median survival time of 6.11 months, while patients whose tumours display a low amount of MnSOD have a median survival time of 12.17 months. To assess the upstream mechanisms that sustain the increase in manganese superoxide dismutase content in brain neuroepithelial tumours, we also studied the expression of p53 in a series of 17 astrocytomas of various grading. In all tested astrocytomas, high manganese superoxide dismutase content is associated with cytoplasmic accumulation of p53. Thus glioblastomas can be divided into two distinct groups on the basis of their content of manganese superoxide dismutase, having 'better' or 'worse' prognosis, respectively. The use of this protein as a marker may help to define therapeutic strategies in the clinical management of glioblastoma.

Regulation of T-cell responses by CNS antigen-presenting cells: different roles for microglia and astrocytes

Analysis of the mechanisms underlying CNS immune surveillance and immunopathology have provided new insights into the intracerebral regulation of immune responses. Here, Francesca Aloisi, Francesco Ria and Luciano Adorini review the role of CNS antigen presenting cells and focus on the control of Th1 and Th2 responses by microglia and astrocytes.

Relative efficiency of microglia, astrocytes, dendritic cells and B cells in naive CD4+ T cell priming and Th1/Th2 cell restimulation

We have compared the efficiency of central nervous system and peripheral antigen-presenting cells (APC) in T cell priming and restimulation. OVA peptide 323 - 339-dependent activation of DO11.10 TCR-transgenic naive CD4+ and polarized Th1 or Th2 cells was assessed in the presence of microglia and astrocytes from the neonatal mouse brain as well as dendritic cells (DC) and B cells purified from adult mouse lymph nodes. DC were the most efficient in inducing naive T cell proliferation, IL-2 secretion and differentiation into Th1 cells, followed by IFN-gamma-preactivated microglia, large and small B cells. Astrocytes failed to activate naive T cells. IFN-gamma-pretreated microglia were as efficient as DC in the restimulation of Th1 cells, whereas IFN-gamma-pretreated astrocytes, large and small B cells were much less efficient. Conversely, Th2 cells were efficiently restimulated by all the APC types examined. During T cell priming, DC secreted more IL-12 than microglia but similar amounts of IL-12 were secreted by the two cell types upon interaction with Th1 cells. The hierarchy of APC established in this study indicates that DC and microglia are the most efficient in the stimulation of naive CD4(+) T cells and in the restimulation of Th1 cells, suggesting that activated microglia may effectively contribute to Th1 responses leading to central nervous system inflammation and tissue damage. These potentially pathogenic responses could be counteracted by the high efficiency of astrocytes as well as microglia in restimulating Th2 cells.

A plasmid family containing two different expression cassettes suitable for immunomodulation and genetic immunization

We have developed an improved eukaryotic expression vector that consists of two distinct, complete, and differentially regulated transcription units. The peculiarities of this prototype vector, named pRC110, are represented by two different strong promoter/enhancer sequences, cytomegalovirus and Rous sarcoma virus, that independently drive transcription of two recombinant cDNAs, which may be easily cloned into specific rare restriction sites. Moreover, we describe a simple way to introduce an optimal translational start site context 5' to any peptide to be cloned in our vectors, thus allowing the correct and efficient expression of even a single part of a larger gene or a short synthetic peptide lacking its own AUG and neighboring regions. We demonstrate the in vivo expression efficacy of pRC110 for use in genetic vaccination through direct intramuscular gene transfer: specific antibodies are raised against one of the encoded peptides 3 weeks after muscle injection, and efficient transcription of the other syngeneic cDNA, mouse interleukin-2, is shown. The development of a "family" of vectors directly deriving from pRC110 is also described, with the common property that one of the encoded proteins may modulate the effects of the other. We recommend the use of pRC110 for genetic immunization and immunological response studies, when the concomitant local production of an immunogenic peptide and of a syngeneic immunomodulating cytokine is required.

Th1 cells induce and Th2 inhibit antigen-dependent IL-12 secretion by dendritic cells

Dendritic cells are the most relevant antigen-presenting cells (APC) for presentation of antigens administered in adjuvant to CD4+ T cells. Upon interaction with antigen-specific T cells, dendritic cells (DC) expressing appropriate peptide-MHC class II complexes secrete IL-12, a cytokine that drives Th1 cell development. To analyze the T cell-mediated regulation of IL-12 secretion by DC, we have examined their capacity to secrete IL-12 in response to stimulation by antigen-specific Th1 and Th2 DO11.10 TCR-transgenic cells. These cells do not differ either in TCR clonotype or CD40 ligand (CD40L) expression. Interaction with antigen-specific Th1, but not Th2 cells, induces IL-12 p40 and p75 secretion by DC. The induction of IL-12 production by Th1 cells does not depend on their IFN-gamma secretion, but requires direct cell-cell contact mediated by peptide/MHC class II-TCR and CD40-CD40L interactions. Th2 cells not only fail to induce IL-12 secretion, but they inhibit its induction by Th1 cells. Unlike stimulation by Th1, inhibition of IL-12 production by Th2 cells is mediated by soluble molecules, as demonstrated by transwell cultures. Among Th2-derived cytokines, IL-10, but not IL-4 inhibit Th1-driven IL-12 secretion. IL-10 produced by Th2 cells appears to be solely responsible for the inhibition of Th1 -induced IL-12 secretion, but it does not account for the failure of Th2 cells to induce IL-12 production by DC. Collectively, these results demonstrate that Th1 cells up-regulate IL-12 production by DC via IFN-gamma-independent cognate interaction, whereas this is inhibited by Th2-derived IL-10. The inhibition of Th1 -induced IL-12 production by Th2 cells with the same antigen specificity represents a novel mechanism driving the polarization of CD4+ T cell responses.

Microglia are more efficient than astrocytes in antigen processing and in Th1 but not Th2 cell activation

Microglia and astrocytes, two glial cell populations of the central nervous system, present Ag and stimulate T cell proliferation, but it is unclear whether they preferentially activate Th1 or Th2 responses. We have investigated the efficiency of microglia and astrocytes in the presentation of OVA peptide 323-339 or native OVA to Th1 and Th2 cell lines from DO11.10 TCR transgenic mice. Upon stimulation with IFN-gamma, microglia express MHC class II molecules, CD40, and ICAM-1 and efficiently present OVA 323-339, leading to T cell proliferation and production of IL-2 and IFN-gamma by Th1 and of IL-4 by Th2 cells. IFN-gamma-treated astrocytes, which express MHC class II and ICAM-1, present OVA 323-339 less efficiently to Th1 cells but are as efficient as microglia in inducing IL-4 secretion by Th2 cells. However, astrocytes are much less potent than microglia in presenting naturally processed OVA peptide to either T cell subset, indicating inefficient Ag processing. The capacity of astrocytes and microglia to stimulate Th1 and Th2 cells depends on their MHC class II expression and does not involve ICAM-1, B7-1, or B7-2 molecules. However, CD40-CD40L interactions contribute to Th1 activation by microglia. These data suggest that microglia may play a role in the activation of Th1 and Th2 cells, whereas astrocytes would restimulate mainly Th2 responses in the presence of appropriate peptides. This differential capacity of brain APC to restimulate Th1 and Th2 responses may contribute to the reactivation and regulation of local inflammatory processes during infectious and autoimmune diseases.

Normal B cells fail to secrete interleukin-12

Interleukin-12 is a key regulatory cytokine produced by antigen-presenting cells (APC) which drives the development of interferon-gamma (IFN-gamma)-producing cells and promotes cell-mediated immunity. Following subcutaneous immunization with protein antigen in adjuvant, dendritic cells (DC) but not small nor large B cells in immune lymph nodes express antigenic complexes and secrete substantial amounts of bioactive IL-12 p75 upon antigen-specific interaction with T cells. We have analyzed secretion of IL-12 p40 and p75 by cell populations enriched in DC, macrophages or B cells in response to nonspecific stimulation or to interaction with antigen-specific CD4+ cells. These APC populations do not produce IL-12 constitutively but, upon stimulation with heat-fixed Staphylococcus aureus and IFN-gamma, IL-12 p40 and p75 are secreted by DC and macrophages, whereas B cells fail to produce IL-12. B cells also fail to secrete IL-12 in response to stimulation with LPS and IFN-gamma. Co-culture with CD4+ T hybridoma cells and antigen induces IL-12 secretion by DC. Up-regulation of IL-12 secretion by interaction with antigen-specific CD4+ T cells is abrogated by anti-class II monoclonal antibodies (mAb), by soluble CD40 molecules and by anti-CD40 ligand mAb, demonstrating a positive feedback between T cells and DC mediated by TCR-peptide/class II and by CD40-CD40 ligand interactions. Expression of class II and CD40 molecules is comparable in B cells and DC, and both APC types activate CD4+ T cells. Yet, even upon interaction with antigen-specific T cells, B cells fail to secrete IL-12. The capacity of B cells to present antigen but not to secrete IL-12 may explain their propensity to selectively drive T helper type 2 cell development.

The mode of protein antigen administration determines preferential presentation of peptide-class II complexes by lymph node dendritic or B cells

We have compared the capacity of dendritic cells (DC) and B cells to present peptide-class II complexes following administration of protein in adjuvant or in soluble form. Three different antigen-presenting cell (APC) populations were separated from draining lymph node cells from mice immunized s.c. with hen egg-white lysozyme (HEL) in adjuvant or with adjuvant only followed by soluble HEL: DC (N418+, class II+, B220-, low buoyant density), large B cells (B220+, low buoyant density) and small B cells (B220+, high buoyant density). HEL peptide-class II complexes displayed by these APC were evaluated by their capacity to activate HEL-specific T hybridoma cells. Following immunization with HEL in adjuvant, DC are the only lymph node APC population expressing detectable HEL peptide-class II complexes. Conversely, after i.v. administration of soluble HEL in mice previously injected with adjuvant only, lymph node B cells are much more efficient than DC in presenting peptide-class II complexes to T cells. Therefore, different modes of protein antigen administration lead to selective expression of antigenic complexes by different APC populations. These data correlate with the observation that, unlike B cells, DC recruited in lymph nodes of mice injected with adjuvant only present in vitro processed protein antigen much less efficiently than synthetic peptides, probably as a consequence of their maturation in vivo.

The level of MnSOD is directly correlated with grade of brain tumours of neuroepithelial origin

The oxy-radical scavenger enzyme manganese superoxide dismutase (MnSOD) may act in the capacity of a tumour-suppressor gene. To address the issue of its role in tumour transformation and progression in vivo, we evaluated the content of this enzyme in 33 brain tumours of neuroepithelial origin with different degrees of differentiation (WHO grade II-IV) by means of Western blot and immunohistology. Our results show that immunoreactive MnSOD increases in a direct relationship with tumour grade and is therefore inversely correlated with differentiation. The increase in induced at a pretranscriptional level and is apparently specific to brain tumours of neuroepithelial origin. Approximately 30% of grade IV tumours display low levels of MnSOD content, and preoperative radiotherapy and brachytherapy result in low amounts of enzyme. Based upon these observations, we suggest that MnSOD cannot be considered a classical tumour-suppressor gene.

Dendritic cells but not B cells present antigenic complexes to class II-restricted T cells after administration of protein in adjuvant

We have analyzed the relative contribution of dendritic cells (DC) and B cells in the presentation of peptide-class II complexes in an inflammatory situation in vivo. Draining lymph node cells from mice immunized subcutaneously with hen egg-white lysozyme (HEL) in adjuvant display HEL peptide-major histocompatibility complex class II complexes able to stimulate, in the absence of any further antigen addition, specific T hybridoma cells. The antigen-presenting capacity of three different antigen-presenting cell (APC) populations recruited in lymph nodes, DC (N418+, class II+, B220-, low buoyant density), large B cells (B220+, low buoyant density), and small B cells (B220+, high buoyant density), was analyzed. After immunization with HEL in adjuvant, DC are the only lymph node APC population expressing detectable HEL peptide-class II complexes. These results indicate that lymph node DC and not B cells are the APC initiating the immune response in vivo after administration of antigen in adjuvant.

Cord blood mononuclear cell responsiveness to beta-lactoglobulin: T-cell activity in 'atopy-prone' and 'non-atopy-prone' newborns

We have studied the T-cell-mediated response to the major allergen of cow's milk, in a group of newborns at risk of developing cow's milk allergy, and in a control group. Before any atopic status has developed, we observe beta-lactoglobulin-specific primary proliferation only in the group at risk for food-related allergies. In this group, the capability to proliferate is not due to placental transmission of 'factors' from allergic mothers. The recognition of the tested beta-lactoglobulin peptides does not show major differences between the responder and nonresponder populations. In the responder population, the response to p145-161 appears linked to a primary response to ovalbumin, another frequent food allergen. On the basis of our findings, we propose a model in which development of allergic diseases is linked to an alteration of T-cell activation through the engagement by the antigen; the HLA phenotype determines the allergen(s) involved, and other genetic or environmental factors dictate the clinical characteristics of the disease.

Failure of presented, non-dominant self epitope to induce tolerance: implications for autoimmune diseases

It has been observed that a hierarchy exists among epitopes such that fewer epitopes are actually involved in the induction of T cell response and tolerance than there are epitopes available in a given antigen. Some epitopes which are "cryptic" for immune activity within the protein, are nevertheless able to elicit a response if administered alone and can also be used to by-pass tolerance. We report that tolerance to a self protein shows the same phenomenon seen for non self proteins. In fact, we elicit a proliferative response toward a predicted minor cryptic epitope, to which animals are clearly not self-tolerant. The minor epitope escapes the induction of tolerance to self proteins more easily than the major epitopes, since we cannot elicit proliferative response to the major epitope. A striking feature of our results however is that lack of self tolerance to the minor epitope appears as not being due to the failure of presentation of this epitope in normal, healthy animals.

Monoclonal antibody 35.8 recognizes human, mouse and rat MnSODs in western blot and immunostaining

MnSOD is an antioxidant enzyme whose decrease in activity appears involved in tumorigenesis. We had previously reported the production of a monoclonal antibody, named 35.8, against rat MnSOD. In the present paper we show that it recognizes human and mouse MnSODs, although with different detection limits. We also use the antibody for immunofluorescence studies and observed that the antibody yields a positive staining of a non-nuclear protein, in rat and human organs where high concentration of MnSOD activity have been reported, and a lack of staining in rat kidney where MnSOD activity is decreased. Two tumors, an experimental rat hepatocarcinoma and a human liver metastasis from a gastrointestinal adenocarcinoma, are found negative for immunostaining.

Preparation of a monoclonal antibody against rat MnSOD, using a COOH-terminal peptide

In the present paper we report the production of a monoclonal antibody against rat MnSOD, a supposed tumor-suppressor protein, using a purified synthetic peptide encompassing amino acids 184-198 to immunize mice, without conjugation to a carrier. The resulting antibody is able to recognize the native form of the protein, since it can immunoprecipitate the MnSOD activity in rat liver homogenate. In Western blot studies, the antibody recognizes a protein of 24 KD M(r), whose concentration varies according to the MnSOD activity and it apparently recognizes also human and mouse MnSODs. The protocol of immunization gives high yield of secreting lines. This monoclonal antibody will allow the detection of structural and functional alterations of MnSOD.

[Essential mixed cryoglobulinemia with liver involvement: a still open problem]

Essential mixed cryoglobulinemia (EMC) is a syndrome characterized by cryoglobulinemia and clinical features including purpura, arthralgia, asthenia (Meltzer-Franklin syndrome) without evidence of any systemic disease Liver involvement in the course of EMC is described in 50-84% of patients. It consists of mild silent hepatosplenomegaly and slightly rise of serum amino transferase. Eleven patients with clinical and laboratory findings suggestive for EMC (five type II and six type III) underwent percutaneous liver biopsy to evaluate the degree of liver involvement. Two liver cirrhosis, two chronic active hepatitis, one chronic persistent hepatitis and a case of hepatic steatosis were found. A type III cryoglobulinemia was present in four of the six patients with liver involvement. All the patients were Hbs Ag negative but three of them were Hbs Ab positive. The pathogenesis of liver involvement in the course of EMC is still now uncertain. The authors believe that a previous HBV infection plays no role in the pathogenesis of EMC syndrome. This syndrome must be considered different from mixed cryoglobulinemia secondary to chronic liver disease. They suggest that liver biopsy is mandatory during the course of EMC even when clinical and laboratory data are silent.

Immunological activity of covalently linked T-cell epitopes

Immune responses to proteins necessarily involve the recognition by T lymphocytes of a peptide or peptides derived from a protein complexed with a major histocompatibility antigen. The T-cell response of BALB/c mice to the bacteriophage lambda cI repressor protein (residues 1-102) is directed predominantly towards the epitope contained within a single peptide encompassing residues 12-26. Similar phenomena of immunodominance of a particular peptide have also been observed in other protein systems. The mechanisms that have been suggested to account for the focusing of the T-cell response are partial deletion in the T-cell repertoire, biased antigen processing, and competition for binding to the presenting molecule, the major histocompatibility complex encoded class II transplantation antigen. In a model system with a polypeptide containing two synthetically linked immunologically active epitopes, we now demonstrate the existence of a hierarchy between these epitopes, so that the immune response elicited is directed mainly towards the more immunogenic epitope, whereas the less immunogenic epitope elicits little or no T-cell reactivity. In addition, the same hierarchy of dominance is also apparent when the polypeptide is used to induce tolerance in the periphery in adult mice. The chimaeric peptide can induce tolerance only towards the more immunogenic epitope. These experiments indicate that the rules governing antigen processing and presentation that result in T-cell activation are apparently the same as the rules that govern the processes resulting in the induction of tolerance.

Chromatographic and electrophoretic studies of immune complexes in non-A, non-B hepatitis

Immune complexes isolated from two patients with chronic non-A, non-B hepatitis, one patient with acute non-A, non-B hepatitis and one patient with juvenile rheumatoid arthritis were examined by means of a combined chromatographic and electrophoretic method. Both analyses showed the presence of complexes consisting of IgG, IgM, complement c1q factor and albumin; no antigen constituents were detected. The IgG-to-IgM ratio varied from 1:1 to 4:1, suggesting that one could be dealing with complexes of both IgG-IgM and IgG-IgG types. Moreover, the detectable presence of c1q factor might indicate that such complexes were capable of activating complement.