Imunologia Celular

Interesse da Investigação

The Cellular Immunology Unit studies mechanisms able to induce and maintain immune tolerance. We study diseases, or animal models of human pathologies, where the immune system has an inappropriate action, such as autoimmunity, transplantation or allergy. We aim to reprogramme the immune system, inducing the expansion of regulatory T cells capable of reinstating the tolerance state. We always strive to validate our experimental results in collaboration with clinical scientists.

Membros do Grupo

Projecto de Investigação

Tolerance induction in autoimmunity: reprogramming the immune system with monoclonal antibodies.

Rheumatoid arthritis (RA) is a chronic systemic inflammatory disease of unknown aetiology, afflicting about 1% of the world population, and characterized by synovial membrane inflammation in multiple joints. There is evidence for a role for arthritogenic CD4+ T lymphocytes in the pathogenesis of the disease, although other cell types such as B cells, fibroblasts and macrophages also seem to be involved in disease.
The current treatment of RA is based on non-curative immunosuppressive and anti-inflammatory agents, including biological drugs such as monoclonal antibodies (mAbs) and soluble receptors targeting pro-inflammatory cytokines, like tumor necrosis factor-alpha (TNF-a). But these treatments do not work for all patients and, more importantly, can have severe side effects. Given the critical role of arthritogenic T cells in the pathogenesis of RA, alternative therapeutic strategies specifically targeting T cells, such as mAbs, have been proposed. However, until now, preclinical testing of mAbs relevant for RA has been hampered by the lack of animal models with spontaneous and chronic autoimmune arthritis. But recently mice were described, harbouring a mutated ZAP-70 gene leading to abnormal thymic T-cell selection, that spontaneously develop a chronic disease remarkably similar to human RA (SKG mice; Sakaguchi N et al; Nature 2003; 426:454).
We are using our experience with tolerogenic mAbs targeting T cells to investigate their ability to reprogram the immune system, and consequently treat arthritis in SKG mice. We have recently shown in mice that co-receptor blockade, co-stimulatory blockade, and more efficiently, a combination of both are effective to induce long-term tolerance to skin transplants (Graca L et al; PNAS 2004; 101:10122). We use anti-CD4, anti-CD40L and anti-OX40L mAbs, to investigate if these mAbs can lead to prevention and treatment of autoimmune arthritis rather than simply controlling inflammation (as with anti-TNFa therapy).
We are also investigating the cellular and molecular mechanisms underlying autoimmunity and tolerance, by comparing the function of T cells and cytokines in disease-free animals (treated SKG and wild type mice) and SKG mice that develop arthritis. We perform adoptive transfer studies of pathogenic and protective cells into lymphopenic hosts as a strategy to isolate critical cellular and molecular components preventing autoimmunity. We will also determine whether the features of dominant tolerance, mediated by regulatory T cells and transforming growth factor-beta (TGF-b), that we have previously described for transplantation tolerance, can also be demonstrated in the control of autoimmune arthritis.
In addition, we have been collaborating with H. Waldmann’s group (University of Oxford) in evaluating in SKG mice molecular markers previously found in transplantation tolerance by serial analysis of gene expression (SAGE) (Cobbold SP et al; Immunol Rev 2003; 196:109). In a second stage, validation of putative markers for tolerance/autoimmunity will be performed in RA patients at Hospital Santa Maria, Lisbon.

Projecto de Investigação

Tolerance induction with monoclonal antibodies in food allergy

Food allergy is a potentially life-threatening disease which is becoming increasingly frequent. Peanuts and other tree nuts account for the majority of the fatal and near-fatal food-induced anaphylactic reactions in sensitized adults and children. Unlike other childhood food allergies, such as egg or cow’s milk allergy, peanut allergy is rarely outgrown. At this time allergen avoidance is the only therapeutic option given the high risk of a life-threatening reaction after the exposure to even minute amounts of the allergen, which prevents allergic desensitization.
It is known that the clinical features of peanut allergy are a consequence of acute IgE-mediated reactions in sensitized individuals. The production of IgE is part of a Th2 type immune response driven by CD4+ T cells. Given the severity of the disease in humans, the study of putative new preventive or curative treatments has to rely on animal models. Wesley Burks and colleagues have developed a murine model of peanut induced anaphylaxis that allows these studies (Li et al; J Allergy Clin Immunol 2000; 106:150).
We plan to use our experience with tolerogenic mAbs targeting T cells to investigate their ability to reprogram the immune system, preventing the pathogenic Th2 response, and consequently abrogating the pathologic response in the animal model of peanut-induced anaphylaxis. We have recently shown in mice that co-receptor blockade, co-stimulatory blockade, and more efficiently, a combination of both are effective to prevent transplant rejection by inducing long-term tolerance to skin grafts (Graca L et al; PNAS 2004; 101:10122). Furthermore, in collaboration with Pat Holt’s laboratory we have shown that CD40L mAbs are efficient in preventing allergic lung inflammation, induced in mice with ovalbumin (Graca L, unpublished). We will use anti-CD4, anti-CD40L and anti-OX40L mAbs, to investigate if these mAbs can lead to prevention and treatment of peanut allergy, and to study their mechanism of action.
We will investigate the cellular and molecular mechanisms underlying the allergic response and tolerance, by comparing the function of T cells and cytokines in disease-free animals (non-sensitized mice), sensitized animals treated and sensitized mice treated with tolerogenic mAbs. We will perform adoptive transfer studies of putative pathogenic and protective spleen cells into lymphopenic hosts as a strategy to define critical cellular and molecular components preventing allergy. We will also determine whether the features of dominant tolerance, mediated by regulatory T cells and transforming growth factor-beta (TGF-b), that we have previously described for transplantation tolerance, can also be demonstrated in the control of peanut-induced allergy.
In a second stage, validation of putative cellular and molecular markers for tolerance/allergy will be performed in patients at the Hospital Santa Maria, Lisbon.

Funding

POCI/SAU-MMO/55974/2004
Tolerance induction in autoimmunity: reprogramming the immune system with monoclonal antibodies

Colaboradores

Sir William Dunn School of Pathology, University of Oxford, U.K.
Herman Waldmann

Telethon Institute for Child Health Research, University of Western Australia, Perth, Australia.
Patrick J. Holt
Phillip Stumbles

Unidade de Artrite Reumatóide, Instituto de Medicina Molecular, Lisboa; and Serviço de Reumatologia, Hospital de Santa Maria, Lisboa.
João Eurico Fonseca

Los Alamos National Laboratory, New Mexico, USA.
Ruy M. Ribeiro

Publicações

Graça, L. (2005). New tools to identify regulatory T cells. European Journal of Immunology 35 :1678-1680

Graça, L., Chen, T.C., Le Moine, A., Cobbold, S.P., Howie, D., Waldmann, H. (2005). Dominant transplantation tolerance: activation thresholds for peripheral generation of regulatory T cells. Trends in Immunology 26 :130-135

Cobbold, S.P., Castejon, R., Adams, E., Zelenika, D., Graça, L., Humm. S., Waldmann, H. (2004). Induction of foxP3+ regulatory T cells in the periphery of T cell receptor transgenic mice tolerized to transplants. Journal of Immunology 172 :6003-6010

Graça, L., Le Moine, A., Lin, C-Y., Fairchild, P.J., Cobbold, S.P., Waldmann, H. (2004). Donor-specific transplantation tolerance: the paradoxial behavior of CD4+CD25+ T cells. Proceedings of the National Academy of Sciences USA 101 :10122-10126

Graça, L., Le Moine, A., Cobbold, S.P., Waldmann, H. (2003). Dominant Transplantation Tolerance. Current Opinion in Immunology 15 :499-506

Graça, L., Cobbold, S.P., Waldmann, H. (2002). Identification of regulatory T cells in tolerated allografts. The Journal of Experimental Medicine 195 :1641-6

Graça, L., Thompson, S., Lin, C-Y., Adams, E., Cobbold, S.P., Waldmann, H. (2002). Both CD4+CD25+ and CD4+CD25- regulatory cells mediate dominant transplantation tolerance. The Journal of Immunology 168 :5558-65

Lin, C-Y.*, Graça, L.*, Cobbold, S.P., Waldmann, H. (2002). Dominant transplantation tolerance impairs CD8+ T cell function but not expansion. Nature Immunology. 3 :1208-13

Graça, L., Honey, K., Adams, E., Cobbold, S.P., Waldmann, H. (2000). Cutting Edge: Anti-CD154 Therapeutic Antibodies Induce Infectious Transplantation Tolerance. The Journal of Immunology 165 :4783-6