Biomedical subjects

L V Rizzo

Publications and source records attributed to L V Rizzo.

At least 37 records · Page 2Linked to original sources

PubMed1998

Cytokine production profile of heart-infiltrating T cells in Chagas' disease cardiomyopathy.

The hallmark of chronic Chagas' disease cardiomyopathy (CCC) is the finding of a T cell-rich inflammatory mononuclear cell infiltrate in the presence of extremely few parasites in the heart lesions. The scarcity of parasites in affected heart tissue casts doubt on the direct participation of Trypanosoma cruzi in CCC heart tissue lesions, and suggests the possible involvement of autoimmunity. The cells in the infiltrate are presumably the ultimate effectors of tissue damage, and there is evidence that such cells recognize cardiac myosin in molecular mimicry with T. cruzi proteins rather than primary reactivity to T. cruzi antigens (Cunha-Neto et al. (1996) Journal of Clinical Investigation, 98: 1709-1712). Recently, we have studied heart-infiltrating T cells at the functional level. In this short review we summarize the studies about the role of cytokines in human and experimental T. cruzi infection, along with our data on heart-infiltrating T cells in human Chagas' cardiomyopathy. The bulk of evidence points to a significant production of IFN-gamma and TNF-alpha which may be linked to T. cruzi-induced IL-12 production.

Animals↗

PubMed1997

Genetic susceptibility to experimental autoimmune uveitis involves more than a predisposition to generate a T helper-1-like or a T helper-2-like response.

This study examines whether genetic susceptibility vs resistance to experimental autoimmune uveoretinitis (EAU) in mice is associated with dominant type 1 vs type 2 cytokine response profiles. Mice from six strains were immunized with the uveitogenic retinal Ag IRBP. EAU was evaluated by histopathology. As judged by disease scores, three of the strains were susceptible, one was minimally susceptible, and two were resistant. Ag-specific type 1 vs type 2 cytokine responses (protein and/or mRNA) in draining lymph node cells, and IgG2a vs IgG1 Ab isotypes to IRBP, were measured as indicators of Th1-like vs Th2-like responses, respectively. The three susceptible strains (B10.A, C57BL/10, and BALB/k) showed a dominant Th1-like response profile characterized by high IFN-gamma and IL-12p40 (but not IL-4) responses, and a predominance of IgG2a Abs. The minimally susceptible strain (A/J) had an IFN-gamma response detectable only at the mRNA level, but produced predominantly IgG2a Abs. One of the two resistant strains (BALB/c) showed a characteristic Th2-like response with dominant Ag-specific IL-4 and IL-10 responses but no IFN-gamma, and predominantly IgG1 Abs. However, the other resistant strain (AKR) did not show a Th2-dominated response pattern, in that it had low, or no, IL-4 and IL-10 responses, and made predominantly IgG2a Abs to IRBP. These results suggest that whereas a Th1 response is required for susceptibility, resistance is not dependent on a Th2 response pattern. We suggest that regulatory influences other than skewing the response toward the Th2 pathway may be equally effective at conferring genetic resistance to EAU.

Animals↗

PubMed1997

IFN-gamma-deficient mice develop experimental autoimmune uveitis in the context of a deviant effector response.

Experimental autoimmune uveitis (EAU) is a T cell-mediated disease that targets the neural retina and serves as a model of human uveitis. Uveitogenic effector T cells have a Th1-like phenotype (high IFN-gamma, low IL-4), and genetic susceptibility to EAU is associated with an elevated Th1 response. Here we investigate whether the ability to produce IFN-gamma is necessary for the development of EAU by immunizing IFN-gamma-deficient (GKO) mice with the uveitogenic protein interphotoreceptor retinoid binding protein (IRBP) and characterize the associated immunologic responses. GKO mice developed EAU comparable in severity and incidence to that of their wild-type littermates. However, the cytokine profile in their uveitic eyes as well as the cytokines produced by primed lymph node cells in response to IRBP showed a distinct profile: undiminished TNF-alpha and elevated IL-5, IL-6, IL-10, and lymphotoxin (but not IL-4) responses. The inflammatory infiltrate in GKO eyes contained an excess of granulocytes and IL-5- and IL-6-producing cells, but uveitic GKO mice did not up-regulate inducible nitric oxide synthase. GKOs had enhanced lymphocyte proliferation and delayed-type hypersensitivity responses to IRBP. Histology of the delayed-type hypersensitivity lesion in GKO had superimposed elements of an allergic-like response. Anti-IRBP Ab isotypes of GKO mice showed a reduction of IgG2a, but no enhancement of IgG1. Comparison of responses in +/+ and +/- wild-type mice revealed some limited evidence of a gene-dose effect. We conclude that IFN-gamma is not required for priming of pathogenic T cells or for effecting the retinal damage and photoreceptor loss typical of EAU. However, what appears to be a grossly similar disease is caused in the GKO by a deviant type of effector response.

Animals↗

PubMed1997

Uveitogenicity is associated with a Th1-like lymphokine profile: cytokine-dependent modulation of early and committed effector T cells in experimental autoimmune uveitis.

This study addresses the nature of the pathogenic effector T cell in experimental autoimmune uveoretinitis and the effect of different cytokines on these cells in vitro. Lymph node cells of B10.RIII mice immunized with the uveitogenic peptide 161-180 of interphotoreceptor retinoid binding protein were cultured with the peptide with or without IL-12, IL-4, or anti-IL-4. An antigen-specific T cell line was subsequently derived from these cells. Primary cultures of immune lymph node cells stimulated with the peptide proliferated and produced IL-2 and some IL-4, but no IFN-gamma. The addition of recombinant IL-12 resulted in abundant production of IFN-gamma, which was blocked by the addition of IL-4 and was enhanced by anti-IL-4. Only those cultures that produced IFN-gamma in vitro were uveitogenic in vivo. A long-term uveitogenic T cell line, initially derived in the presence of IL-12, produced IFN-gamma and IL-2, but not IL-4, and was CD4+ (Th1-like). Antigen-specific proliferation and IFN-gamma production of the line were enhanced by exogenous IL-4, TGF-beta, IL-2, IL-6, IL-7, and IL-9 and were inhibited by IL-10 and TNF-alpha. Our results provide support for the hypothesis that the uveitogenic effector T cell has a Th1-like phenotype. Furthermore, the data suggest that the effects of the cytokine milieu on fully differentiated Th1 effectors may differ considerably from their effects on less mature stages of antigen-specific T cells.

Amino Acid Sequence↗

PubMed1997

Murine postthymectomy autoimmune oophoritis develops in association with a persistent neonatal-like Th2 response.

Autoimmune oophoritis develops in some patients despite evidence of impaired cellular immunity. Here, using the murine postthymectomy model of autoimmune oophoritis, we investigate the hypothesis that neonatal thymectomy induces autoimmune oophoritis by disrupting the normal postnatal balance of T helper cell regulation. Stimulated CD4+ splenic lymphocytes from adult mice sham-operated as neonates produced the expected T helper type 1 (Th1) predominant response normally seen in adult mice (low levels of interleukin-4 and high levels of interferon gamma). In contrast, cells from adult mice thymectomized as neonates produced an inappropriate neonatal-like Th2-predominant response (high levels of interleukin-4 and low levels of interferon-gamma). Manipulations that restored the postnatal shift to an adult Th1-dominant pattern ameliorated the autoimmune oophoritis. Thus, neonatal thymectomy abrogates the postnatal shift to a Th1-dominant pattern, and the resulting persistent neonatal-like Th2-dominant response is tightly associated with the development of postthymectomy autoimmune oophoritis. These results (i) suggest that the postnatal shift to the normal adult Th1/Th2 balance is established by a thymus-dependent process and (ii) raise the possibility that specific genetic defects, as yet to be determined, might mimic the effect of neonatal thymectomy in this model, impair the development of normal Th1/Th2 balance, and be a cause autoimmunity. These results hold implications for the pathogenesis and possibly for the therapy of autoimmune polyglandular failure in humans.

Adoptive Transfer↗

PubMed1997

The effects of anesthesia with thiopental on T lymphocyte responses to antigen and mitogens in vivo and in vitro.

In this study we show that antigen-specific lymphocyte proliferation and interleukin (IL)-2 production by peripheral blood lymphocytes from patients under thiopental anesthesia are significantly depressed. In contrast, mitogen-induced lymphocyte proliferation and IL-2 secretion are not depressed. We have also shown that tetanus toxoid (TT) specific CD4+ T cell clones, with a known cytokine production profile, were sensitive to the inhibitory effects of thiopental and exhibited decreased proliferation to TT as well as decreased secretion of IL-2. We observed no difference regarding IL-4 production by these clones. The data suggest that the immunosuppressive effect of thiopental is confined to antigen-specific responses. In addition, we have shown that whereas IL-2 and interferon-gamma production is dramatically impaired by the drug, IL-4 production is not significantly altered. This last finding has important implications regarding the type of immune response that is most affected by this anesthetic agent. In spite of the transient decrease in antigen-driven IL-2 synthesis, no clinical evidence of infection was noted in any healthy patient.

Adolescent↗

PubMed1997

T cell mechanisms in experimental autoimmune uveoretinitis: susceptibility is a function of the cytokine response profile.

This study addresses the question whether susceptibility versus resistance to experimental autoimmune uveoretinitis (EAU) is connected to a Th1-type (interferon-gamma high, interleukin-4 low), versus a Th2-type (IFN-gamma low, IL-4 high) response. Primed lymph node cells of susceptible Lewis rats produced IFN-gamma in response to antigen in culture and transferred EAU to syngeneic recipients, whereas lymph node cells of resistant F344 rats made no IFN-gamma and did not transfer disease. Reversal of the disease pattern, by treatment of F344 rats with B. pertussis toxin and immunisation of Lewis rats with antigen in incomplete Freund's adjuvant, resulted in a parallel reversal of these response patterns. Neither strain produced significant IL-4 responses. A study of the response patterns in mice confirmed that high Th1 responders were susceptible, whereas low Th1 responders and Th2 responders were resistant. We conclude that susceptibility to EAU is connected with a Th1-dominant response, but resistance can involve either a 'null', F344-like response (Th1-low/Th2-low) or a Th2-dominant response.

Adoptive Transfer↗

PubMed1996

Reconstitution of germinal center formation in nude mice with Th1 and Th2 clones.

We investigated the ability of hemocyanin (KLH)-specific cloned CD4+ T cells expressing defined cytokine profiles to support germinal center (GC) formation in syngeneic athymic recipients in response to hapten-KLH challenge. Th1 clones producing IL-2 and IFN-gamma did not by themselves increase GC production above background, while Th2 cells producing IL-4 and IL-5 did. However, the combination of Th1 and Th2 cytokines was more effective than Th2 cytokines alone, suggesting a synergistic effect in this aspect of their help for B cells. In contrast to GC formation, antibody production could be induced with Th1 or Th2 clones given separately (Th1 clones inducing IgG2a, and Th2 clones inducing IgG1 and IgE). These results indicate that the T cell requirements for GC production are different from those for isotype switching and Ig secretion. It is postulated that the synergy between Th1 and Th2 cells in the induction of GC formation reflects the synergy between Th1 and Th2 cytokines, such as IFN-gamma and IL-5, in promotion of GC cell proliferation.

Adoptive Transfer↗

PubMed1996

Interleukin (IL)-4-independent immunoglobulin class switch to immunoglobulin (Ig)E in the mouse.

Immunoglobulin (Ig) class switching in B cells is regulated by stimuli transduced by cytokines and cell-cell contact. Among these stimuli, interleukin (IL)-4 has been considered an absolute prerequisite for class switching to IgE in the mouse. Here we report that IL-4-deficient (IL-4-/-) and wildtype mice had comparably elevated serum IgE levels during the course of a murine retrovirus-induced immunodeficiency syndrome, MAIDS. IgE switching in IL-4-/- mice was also induced by injection of anti-IgD antibody. Treatment with anti-IgD induced germline epsilon (g epsilon) transcripts with comparable efficiency in IL-4-/- mice and controls, but the levels of productive epsilon transcripts (p epsilon) were lower by a factor of 200 and serum IgE levels were lower by a factor of 300 in IL-4-/- mice as compared with controls. Induction of g epsilon after anti-IgD treatment of IL-4-/- mice was unaffected by simultaneous treatment with monoclonal antibodies to IL-4 and IL-4 receptor alpha chain. Infection of IL-4-/- mice with Nippostrongylus brasiliensis, a potent stimulus for IgE production, resulted in induction of g epsilon transcripts; however, p epsilon transcripts were barely detectable and serum IgE was not detected. These findings establish a novel IL-4-independent pathway for IgE switching in the mouse that is strongly activated in retroviral infection but weakly in nematode infection. This pathway appears to be dependent on distinct factors that separately control induction of g epsilon transcription and switch recombination to p epsilon.

Animals↗

PubMed1996

Establishment and characterization of a murine CD4+ T cell line and clone that induce experimental autoimmune uveoretinitis in B10.A mice.

B10.A mice develop experimental autoimmune uveoretinitis after active immunization with the interphotoreceptor retinoid-binding protein (IRBP). CD4+ T cells play an important role in the development of the disease. In this study we have isolated and characterized a CD4+ T cell line and a T cell clone that induce experimental autoimmune uveoretinitis when transferred into naive B10.A mice. The cell line was isolated from draining lymph nodes of IRBP-immunized animals by repeated cycles of IRBP stimulation. The line was shown to be pathogenic after 4 rounds of in vitro stimulation with IRBP at 5 x 10(6) cells/mouse. A T cell clone derived from this line by limiting dilution was shown to be pathogenic when the same number of cells was injected; incidence and severity of disease, however, were much lower. After 16 rounds of IRBP-specific stimulation the cell line was pathogenic at 10(5) cells/mouse. Analysis of the V beta repertoire revealed that at this point the line was mostly composed of V beta 8.2- and V beta 6-positive cells (> 80% of the population). The uveitogenic clone expressed V beta 8.2. Both the T cell line and the clone elaborated an unrestricted lymphokine profile in vitro. However, when these cells were adoptively transferred into naive recipients, mRNA isolated from the uveitic retina showed only Th1 type cytokines. These data help to characterize the nature of pathogenic cells involved in ocular autoimmunity.

Animals↗

PubMed1996

Cytokine-dependent modulation of oral tolerance in a murine model of autoimmune uveitis.

In summary, our data suggest that oral tolerance in the mouse EAU model may occur by anergy/deletion or by suppression, depending on the feeding regimen. Tolerance involving putative regulatory cells appears to require the ability to produce both IL-4 and IL-10, whereas induction of tolerance involving anergy may not require the presence of Il-4 and IL-10. We propose that regulatory cells induced by three feedings of IRBP can be selectively enhanced through the use of cytokines. From the point of view of clinical therapy, it would be worthwhile to explore postimmunization feeding regimens involving administration of IL-4 and IL-10.

Administration, Oral↗

PubMed1996

IL-12 inhibits endotoxin-induced inflammation in the eye.

Interleukin-12 (IL-12) is a heterodimeric cytokine that induces interferon (IFN)-gamma production and an increased generation of Th1 cells. Both IL-12 and IL-12 antagonists are being studied for the treatment of allergic reactions, autoimmune disease and malignancy. The goal of the present experiments was to examine the importance of IL-12 in endotoxin-induced ocular inflammation. The number of inflammatory cells infiltrating eyes with endotoxin-induced uveitis (EIU) was significantly increased in animals treated with intraperitoneal anti-IL-12 antibody when compared to control animals, but there was no difference in infiltrating inflammatory cells in the eyes of animals treated with IL-12 when compared to controls. In contrast, intraocular injection of IL-12 significantly inhibited the development of endotoxin-induced intraocular inflammation. The infiltrating inflammatory cells were reduced in the eyes of animals receiving intraocular IL-12 when compared to controls. Cytokine analysis of the aqueous humor obtained from eyes with EIU showed increased levels of IFN-gamma and decreased levels of IL-6 in eyes receiving intraocular IL-12. These data show that IL-12 has an inhibitory effect on endotoxin-induced inflammation in the eye and suggest that IL-12 can have an immunoregulatory function in some forms of inflammatory disease.

Animals↗

PubMed1996

CD8 T-cells are not essential for the induction of "low-dose" oral tolerance.

To examine whether CD8 T-cells are essential for the induction of "low-dose" oral tolerance, we tested animals deficient in CD8 T-cells, i.e., Lewis rats in which CD8 cells were eliminated by injections of specific antibodies and beta 2m(-/-) mice in which the CD8 cells are scarce and poorly functional. Oral tolerance was induced in the rats by repeated feedings with the uveitogenic retinal S-antigen, while in the mice the fed antigen was ovalbumin. Feeding reduced in both species the specific cellular immune response, measured by the lymphocyte proliferation assay. In the rats, this treatment also inhibited the development of the inflammatory eye disease, experimental autoimmune uveoretinitis. In addition, the levels of specific antibodies in the fed animals were moderately lower than those in their controls. Both the CD8-depleted rats and the beta 2m(-/-) mice resembled their normal controls in demonstrating reduced immune responses following feeding with the corresponding antigen. This observation thus indicates that CD8 T-cells are not essential for the induction of low-dose oral tolerance.

Administration, Oral↗

PubMed1996

Anti-tumor necrosis factor alpha therapy suppresses the induction of experimental autoimmune uveoretinitis in mice by inhibiting antigen priming.

PURPOSE: Experimental autoimmune uveoretinitis (EAU) serves as a model for several immune-mediated diseases that affect the eye in humans. Previous studies indicated that tumor necrosis factor alpha (TNF-alpha) has an important proinflammatory role in EAU and possibly in human uveitis. In this study, the authors investigated the effect of anti-TNF-alpha therapy on EAU in mice. METHODS: Experimental autoimmune uveoretinitis was induced in B10.A mice by immunization with interphotoreceptor retinoid-binding protein (IRBP). The mice were treated with 100 or 300 microliters rabbit antiserum or polyclonal antibodies to human TNF-alpha. The treatment spanned either the afferent or the efferent stage of EAU (days -1, 1, 3, 5, 7, or days 8, 10, 12, 14, 16, respectively). Control animals were injected with preimmune rabbit serum at the corresponding times or were not treated. Three weeks after immunization, EAU was assessed by clinical evaluation and by histopathology. Immunologic responses were assessed by delayed-type hypersensitivity (DTH), lymphocyte proliferation to IRBP, and relative abundance of IRBP-primed splenocytes. RESULTS: The treatment with rabbit anti-TNF-alpha serum significantly ameliorated disease when given during the afferent stage but had no effect when given during the efferent stage of EAU. The effect on DTH, lymphocyte proliferation, and abundance of antigen-reactive cells roughly paralleled the effect on disease. CONCLUSIONS: Neutralization of systemic TNF ameliorates EAU. The effectiveness of afferent treatment in comparison to the treatment during the efferent stage, together with the reduced proliferation and the reduced abundance of IRBP-responsive cells, suggest that interference with afferent-acting processes such as antigen priming is important to achieve protection from EAU by anti-TNF treatment.

Animals↗

PubMed1995

IL-12 induces growth of the IL-4-dependent CT4S line and has a synergistic effect on IL-4-induced CT4S proliferation.

In the course of studies designed to explore the effect of interleukin 12 (IL-12) on the development of experimental autoimmune uveoretinitis (EAU), we observed that supernatants from IL-12-treated cultures of ocular antigen-specific lymphocytes induced proliferation of the interleukin 4 (IL-4)-dependent CT4S line. This result was surprising, as these supernatants were not expected to contain high levels of IL-4. We therefore explored the possibility that IL-12 itself, that remained in the supernatants, could induce proliferation of CT4S cells. In this series of experiments we demonstrate that CT4S cells proliferate to recombinant as well as to naturally produced IL-12, and that IL-4 and IL-12 synergize in supporting proliferation of CT4S cells. The proliferation induced by IL-12, as well as the synergistic effect with IL-4, can be reversed by neutralizing anti-IL-12 antibodies. Proliferation of CT4S can be abrogated completely by a combination of antibodies against IL-4 and IL-12. Our data have important implications for the use of CT4S as a specific bioassay for IL-4, since both IL-4 and IL-12 may be found together in at least some culture supernatants. Furthermore, our results suggest that the CT4S line (or a derivative selected from it) could be used as a bioassay for detection of IL-12 in combination with the specific antibodies.

Animals↗

PubMed1995

Regulation of the interaction between Th1 and Th2 T cell clones to provide help for antibody production in vivo.

On the premise that an individual with an intact immune system has the capability to develop both cellular and antibody immune responses supported by the balance between the lymphokines secreted by T helper (Th) cells, we studied the interaction between different types of Th cell clones in vivo and the parameters that may affect this interaction. We used an adoptive transfer system in which nude or lethally irradiated mice were reconstituted with histocompatible CD4+ keyhole limpet hemocyanin (KLH)-specific T cell clones with defined lymphokine profiles. This approach allowed us to study the effects of the cognate interaction between T and B cells in the presence of a defined set of lymphokines. We demonstrated that the co-transfer of both subsets of Th cells resulted in increased production of IgA, and decreased production of IgE and IgG2a. The concomitant presence of both cell types also increases their functional survival in vivo. We have shown that in the presence of a Th2 clone, higher immunization doses (above 100 micrograms trinitrophenol (TNP)-KLH/mouse) result in increased production of IgE and IgG1. In contrast, when a Th1 clone is present, low immunization doses (less than 50 micrograms TNP-KLH/mouse) resulted in increased production of IgG2a. We were also able to show that the neutralization of interleukin-4(IL-4) and or interferon-gamma (IFN-gamma) was sufficient to abrogate most of the regulatory effects caused by the Th2 or the Th1 clone respectively. Our results indicate that the subset of T cell(s) transferred determines the type of response obtained. In addition, the data presented indicate that the antigen dose used for immunization can modulate the quantitative parameters of the response. Furthermore, we have shown that the interaction between the two subsets of T cells in vivo is characterized by both antagonistic and agonistic effects and that most of the regulatory effects exerted by one subset over the other are mediated by IL-4 or IFN-gamma.

Animals↗

PubMed1995

Immunotolerance and prevention of ocular autoimmune disease.

Immunotherapeutic approaches to autoimmune disease have a common goal of inducing antigen-specific, long-lasting tolerance to autoantigens, without otherwise compromising the immune response. Here we review some of the most interesting experimental advances in this area. We discuss the use of T cell targeting drugs that have been reported to induce long lasting tolerance to ocular antigens. Strategies involving the targeting of idiotypic and clonotypic determinants associated with ocular autoimmunity, such as idiotypic network manipulation and T cell vaccination, are reviewed. The use of cytokines to promote perturbation of the Th1/Th2 balance with its possible implications for treatment of uveitis, is analysed. Finally, we review tolerogenic strategies based on acquisition of tolerance following presentation of antigen through alternative routes, such as injection of antigen into the anterior chamber, intravenous infusion of antigen, and oral administration of retinal antigens. Special emphasis is placed on the last strategy, since there are ongoing clinical trials using oral tolerance as an immunotherapeutic approach to treat autoimmune diseases, among them uveitis.

Animals↗

PubMed1995

Identification of a major pathogenic epitope in the human IRBP molecule recognized by mice of the H-2r haplotype.

PURPOSE: Mice of the H-2b, H-2k, and H-2r haplotypes develop experimental autoimmune uveoretinitis (EAU) after immunization with interphotoreceptor retinoid-binding protein (IRBP) of bovine or monkey origin. The purpose of this study was to identify putative pathogenic epitope(s) of IRBP and to establish their immunodominance within the IRBP molecule. METHODS: Overlapping 20-amino acid peptides, spanning the entire human IRBP molecule, were synthesized and used to immunize C57BL/10 (H-2b), B10.BR (H-2k), and B10.RIII (H-2r) mice. Bovine IRBP was used as a positive control. Experimental autoimmune uveoretinitis was examined by histopathology 21 days after immunization. Immunologic responses were assessed by delayed-type hypersensitivity (DH) and lymphocyte proliferation assays. RESULTS: Peptide 161-180, spanning the sequence SGIPYIISYLHPGNTILHVD, was found to be highly pathogenic for B10.RIII mice but not for the other strains. A dose-response curve showed that peptide 161-180 was maximally pathogenic at 50 micrograms, but incidence and scores were reduced at 10 micrograms. The truncated 13-mer 165-177 was also highly pathogenic (100 to 200 micrograms), suggesting that it contained the pathogenic epitope. Mice immunized with the peptide, or with whole IRBP, had positive DH and lymphocyte responses to the immunizing as well as to the reciprocal antigen. A cell line derived to peptide 161-180 was also pathogenic for B10.RIII mice after adoptive transfer and responded (proliferation) to native IRBP. CONCLUSIONS: High incidence and high severity scores, as well as immunologic cross-recognition of peptide 161-180 and native IRBP in vivo and in vitro, suggest that this peptide contains a major epitope recognized as pathogenic by B10.RIII mice.

Amino Acid Sequence↗