Constantin Bona

Disrupting the IL-4 gene rescues mice homozygous for the tight-skin mutation from embryonic death and diminishes TGF-β production by fibroblasts

The TSK/TSK mutation is embryonic lethal; embryos have been reported to die at 7–8 days of gestational age. Crossing TSK/+, IL-4+/− mice revealed that disrupting one or both IL-4 alleles allowed survival of 29 and 47%, respectively, of TSK/TSK mice. These mice failed to develop cutaneous hyperplasia but did exhibit the emphysema that is found in TSK/+ mice. We showed that IL-4 stimulation of fibroblasts increased the level of transforming growth factor-β (TGF-β) mRNA and that lungs of TSK/+, IL-4−/− mice had substantially less TGF-β mRNA than lungs of TSK/+, IL-4+/+ mice. Thus IL-4 seems to regulate the expression of TGF-β in fibroblasts, providing an explanation for the absence of cutaneous hyperplasia in TSK/+, IL-4Rα−/− and TSK/+, TGF-β+/− mice.

New perspectives on immunointervention in autoimmune diseases

The currently available treatments for autoimmune diseases were not developed with a clear knowledge of the mechanisms involved in the primum movens of the disease process, namely the activation of autoreactive T cells. A new generation of immunosuppressive agents that are potentially useful in the prevention and/or treatment of autoimmunity is being fostered by recent progress in the understanding of antigen presentation to T cells. In this article, contributed by the chairpersons of a recent workshop on the subjects, the potential of new therapeutic approaches targeting the major histocompatibility complex (MHC), T-cell receptor (TCR), CD4/CD8 and CD3 molecules, adhesion molecules, cytokines and cytokine receptors are considered.

Immune response of neonates elicited by somatic transgene vaccination with naked DNA.

Neonates display lower immune responsiveness and higher susceptibility for high-dose tolerance. Quantitative as well as functional differences between the neonatal and adult lymphocytes or antigen presenting cells (APC) respectively, explain the particular immune responsiveness during the early stages of the postnatal development. Reduced numbers of lymphocytes and APCs as well as a modified responsiveness of T cells in neonates, are the main factors that account for the low threshold of tolerance in newborns. Taking into account these particularities, the design of effective vaccines for neonates poses significant difficulties. We hypothesized that a continuous exposure to low doses of antigens may avoid high-zone tolerance and may lead instead, to effective expansion of effector and memory cells. Indeed, inoculation of newborn mice with plasmids encoding nucleoprotein (NP) or hemagglutinin (HA) of influenza virus, led to the priming of specific cytotoxic (CTL), helper (Th) and B cells, rather than induction of unresponsiveness. Mice immunized as neonates with naked DNA and challenged later with lethal doses of influenza virus, displayed significant protection. Thus, DNA immunization may be a promising strategy for vaccination against serious infectious diseases of infants and children.

Direct and indirect suppression induced by anti-idiotype antibody in the inulin-bacterial levan antigenic system

Abstract Our findings on the suppression of anti-inulin [ β (2 → 1) fructosan] antibody synthesis by anti-idiotype antibodies are reviewed in this communication. Treatment with anti-idiotype antibodies leads to suppression of those B cells which can secrete antibodies bearing that idiotype ( direct suppression ). This suppression was achieved in three models: maternally induced, pretreatment of 1-day old BALB/c mice with anti-idiotype antibody and similar treatment of adult BALB/c mice. Maternally and neonatally induced suppression was more profound and longer than suppression in adults. The direct suppression appears to be largely independent of T cell influence. In addition, we report a new phenomenon ( indirect suppression ), which is the inhibition by anti-E109 idiotype antibody of an E109 − antibody response, to antigenic determinants borne on the same carrier molecule as the β (2 → 1 ) fructosan determinant. Indirect suppression provides an important model for probing aspects of the regulation of clonal expression through idiotype specific molecules.

Escape from Self-tolerance Leads to Neonatal Insulin-dependent Diabetes Mellitus

Double transgenic (dTg) mice expressing the hemagglutinin (HA) of influenza virus under the insulin promoter and the TCR specific for the immunodominant CD4 T cell epitope of HA (HA110-120) develop insulin-dependent diabetes mellitus (IDDM). In order to gain information on the breaking down of neonatal self-tolerance we studied the occurrence of IDDM after birth. Our results showed that newborn mice develop fulminant IDDM characterized by occurrence of insulitis as early as 3 days after birth, followed by hyperglycemia by 7 days, and significant hypoinsulinemia by 28 days. The neonatal breakdown of self-tolerance of T cells positively selected in the thymus is supported by the facts that: (i) peripheral HA110-120 specific T cells from neonates are fully functional and proliferated upon stimulation with the nominal peptide, and (ii) peptide-specific T cells were accumulated in the pancreas of dTg mice as early as 3 days after birth. Our results demonstrate that diabetes occurring in young dTg mice is due to early activation of self-reactive T cells immediately after birth. Accumulation of specific T cells in the target organ leads to destruction of pancreatic beta-cells and IDDM. These mice may provide a useful model to evaluate new strategies for the prevention of diabetes.

A peptide-major histocompatibility complex II chimera favors survival of pancreatic beta-islets grafted in type 1 diabetic mice.

Background. Transplantation of pancreatic islets showed a tremendous progress over the years as a promising, new therapeutic strategy in patients with type 1 diabetes. However, additional immunosuppressive drug therapy is required to prevent rejection of engrafted islets. The current immunosuppressive therapies showed limited success in maintaining long-term islet survival as required to achieve insulin independence in type 1 diabetes, and they induce severe adverse effects. Herein, we analyzed the effects of a soluble peptide-major histocompatibility complex (MHC) class II chimera aimed at devising an antigen-specific therapy for suppression of anti-islet T cell responses and to improve the survival of pancreatic islets transplants. Methods. Pancreatic islets from transgenic mice expressing the hemagglutinin antigen in the beta islets under the rat insulin promoter (RIP-HA) were grafted under the kidney capsule of diabetic, double transgenic mice expressing hemagglutinin in the pancreas and T cells specific for hemagglutinin (RIP-HA, TCR-HA). The recipient double transgenic mice were treated or not with the soluble peptide-MHC II chimera, and the progression of diabetes, graft survival, and T cell responses to the grafted islets were analyzed. Results. The peptide-MHC II chimera protected syngeneic pancreatic islet transplants against the islet-reactive CD4 T cells, and prolonged the survival of transplanted islets. Protection of transplanted islets occurred by polarization of antigen-specific memory CD4 T cells toward a Th2 anti-inflammatory response. Conclusions. The peptide-MHC II chimera approach is an efficient and specific therapeutic approach to suppress anti-islet T cell responses and provides a long survival of pancreatic grafted islets.

Thymic Development of CD4+25hi Foxp3+ T-Regulatory Cells Echoes their Suppressogenic Capacity in Periphery

The CD4 + 25 hi Foxp3 + T regulatory (T-reg) cells are naturally-born in thymus and they are critical for maintain- ing the tolerance to self and non-self antigens. Foxp3 is the master-regulatory gene of development and function of this cell subset. Using two mouse strains that share the same MHC class II (H-2 d ) haplotype, we found that Foxp3 is early ex- pressed in the CD3 + 4 - 8 - 25 +/- 44 - (DN3/4) double negative thymocytes. Furthermore, Foxp3 showed a differential kinetics of expression in the thymus of these two strains that were controlled through the rates of proliferation and apoptosis of T- reg precursors, but not by epigenetic alterations at the Foxp3 gene promoter. Faster T-reg proliferation and lower apopto- sis were associated with higher Foxp3 + thymic cell output. Also, faster proliferating T-reg precursors showed lower ex- pression of CD3/TCR complex, leptin receptor, Bad, and Caspase3 early in the DN stage of differentiation. Despite a dif- ferential T-reg thymic output in these two mouse strains, the size of peripheral CD4 + 25 hi Foxp3 + T-reg compartment was homeostatically normalized. However, the Foxp3 + T-reg suppression tested in an autoimmune mouse model for diabetes was stronger in mice with a higher T-reg thymic output. These findings demonstrate a differential thymic development and suppressive capacity of Foxp3 + T-reg cells in two genetic backgrounds regardless the MHC II haplotype. This raises the question of whether a differential suppressogenic capacity of the T-reg compartment may affect the susceptibility to autoimmune disorders in individuals from different ethnic groups.

IDIOTYPE AND LYMPHOCYTES

Publisher Summary This chapter discusses the idiotypic specificity on the receptors of B and T lymphocytes. In a study described in the chapter, PFC-secreting antibodies exhibiting particular IdXs were examined for PFC inhibition by the addition of antiidiotypic antisera to the agarose. In this system, it was shown that the majority of anti-PC PFC carry T15 IdX, antiinulin PFC carry E109 IdX, and anti-streptococcus antibodies exhibit A5A or S117 IdXs. Labeled anti-idiotypic antibodies against rat antiallo-antigens, rabbit anti-bovine RNase, and anti-human myeloma proteins have also been used to determine the percentage of B cells carrying idiotypic specificities. The receptor of rat T cells for alloantigens carry the same idiotypic specificity as rat anti-alloantigens antibodies. T helper cells in mice carrying the idiotypic specificity coded by VH genes are located on T cell receptors. Rabbit T cells binding bovine RNase carry not only the Id specificity of anti-RNase antibodies but also a series allotypes located in the framework of the V H region of rabbit Ig.

LYMPHOCYTES AND IDIOTYPES WORKSHOP SUMMARY

Publisher Summary This chapter discusses the different aspects of lymphocytes and idiotypes. Data showing the genetic control of idiotypic specificity of antibodies against synthetic and natural antigens, the presence of idiotypic determinants of receptors of alloreactive T cells, and the regulation of the immune response by anti-idiotypic antibodies is presented in the chapter. In an experiment described in the chapter, anti-idiotypic antibodies were obtained in guinea pigs immunized with C3H.W anti (T,G)-A-L. Cross-reactive and individual idiotypes of 104E, J-558 and UPC-102 α l-3 dextran myeloma protein were found on μ and γ anti-dextran antibodies produced in Balb/c and Ig lb to e strains. Autoanti-idiotypic antibodies rose in Balb/c mice against 104E idiotype, showing an increased graft resistance for 104E myeloma cells but not J-558 tumor cells. The data suggested that anti-idiotype antibodies might control the expression of both neoplastic and normal B cell clones.