Lymphocyte Physiology

Research Interests

We dedicate most of our efforts to the understanding of the cellular and molecular regulation that ensure the production and maintenance of a healthy immune system.
Autoimmunity and inflammatory immuno-pathologies result from misdirected and exacerbated immune responses, respectively. Several layers of regulation ensure that a healthy immune system discriminates self from non-self components, and, amongst the latter, innocuous commensals and food antigens from infectious agents. Similarly, a healthy immune system relies on robust regulatory mechanisms to return to equilibrium (homeostasis) after an immune challenge or other stresses.
The mechanisms at the basis of these complex regulatory mechanisms are not fully understood, yet their elucidation is essential to the design of effective therapies for autoimmune and immuno-inflammatory diseases, two medical conditions showing dramatic increases in western countries and both caused by “not enough regulation”. Symmetrically, chronic infections, a worldwide health threat, result from impaired immune responses associated with “too much regulation”. Likewise, tumors are, to a large extent, genetically similar to the other cells of the genome and a healthy immune system does not allow efficient immune response targeted at “self components”. Finally, long-term heterologous graft acceptance needs the re-education of the immune system for these genetically different organ and tissues to be assimilated as “self”.
It is our contention that the understanding of the immune system dynamics necessitates a proper vision of the rules that orchestrate 1-the life long generation and shaping of the lymphocyte antigen receptor repertoire, 2- the cross talk between regulators and regulated immune cells and between microbes or tissues and specific components of the immune system. We directly assess these issues in vivo both in healthy mice and in various mouse models of spontaneous or induced (auto-) immune inflammation. Whenever adaptable, parallels studies in humans are considered.

We are looking for post-doctoral fellows to work in this area. If you are interested, please contact Jocelyne Demengeot.

Group Members

Elodie Mohr	Postdoc
	Tel: 21 446 4641
Andreia Lino	Postdoc
	Tel: 21 440 7935
Marie Louise Bergman	Postdoc
	Tel: 21 446 4629
Marie Bonnet	Postdoc
	Tel: 21 440 7935
Ana Catarina Martins	Research Technician
	Tel: 21 440 7935
Aleksandra Gumienny	Research Technician
	Tel: 21 440 7935
Maria De Fátima Pascoal	Research Technician
	Tel: 21 440 7935
Ana Paula Regalado	Research Personnel
	Tel: 21 446 4629
Ricardo Paiva	2007 PGD PhD Student
	Tel: 21 440 7935
Sandra Gama	2008 PGFMA
	Tel: 21 449 7935
Rômulo Areal	2011 PIBS
	Tel: 21 446 4629

Research Project

Effects of the Recombination Activating Genes 1 and 2 on the Vertebrate Genome Stability: Consequences at the Cellular and at the Organism level

RAGs are site specific recombinases that mediate the somatic rearrangements of DNA gene segments encoding the T and B cell receptors. Their activity is essential for lymphocytes differentiation and for the generation of the very large diversity of antigen-receptors. We are investigating three issues related to RAG activities: 1-Hypomorphic mutations in the Rag gene, as in the human Omen syndrome, associate with lymphopenia and result in both immunodeficiency and various immune pathologies, including auto-immunity. There is to date no formal mechanistic explanation for the association of these two pathologies. 2-Abnormal RAG activity has been associated with genomic instability and tumor development, notably in the lymphocyte lineage. The vertebrate genome has been claimed to contain about 105 cryptic recognition signal sequences (RSS), outside of the BCR and TCR loci, that could potentially be bound by the RAGs. Some of these cryptic RSS have been shown to be responsible for aberrant Rag mediated DNA recombination and transposition of specific oncogenes. To which extend aberrant Rag activity promotes tumor formation and tumor progression in lymphoid and non-lymphoid tissues has not been formally addressed. 3- The Rag genes have been proposed to originate from a transposon that integrated the genome of a vertebrate ancestor. The consequence of this horizontal transfer on the vertebrate genome structure has not been evaluated.
To these aims, we have generated transgenic mice in which Rag activity can be induced in lymphoid and non-lymphoid tissues. We also developed new retroviruses that serve as reporters of Rag activity. In addition flies transgenic for the Rag genes are being analyzed and we tentatively develop novel algorithms to identify cryptic RSS in various genomes.

Funding

L’Oréal 2007
Project award to Leonor Morais Sarmento

Terry Fox Cancer 2008
Project award to Leonor Morais Sarmento

Collaborators

IMM, Lisboa
António Jacinto

King's College, London
Marc Dionne

IGC, Oeiras
Computational Genomics Group
José Leal, Paulo Almeida

Research Project

Origins and dynamics of regulatory T cells during inflammatory pathologies

Our original finding that regulatory T cells (Treg) prevent deleterious inflammatory responses and limit also protective immune responses has prompted a major group effort in the past years to identify Tregs activating signals. We had revealed that regulatory T cells are activated, expand, and acquire higher effector efficiency upon (pro-) inflammatory stimuli (reviewed in Demengeot et al, 2006 Springer Semin Immunopathol, 28, 41). This activation is in part mediated by Toll Like Receptors selectively expressed by this subpopulation of T cells but other endogenous inflammatory signals participate in this dynamic. Using various TCR transgenic models, various inflammatory triggers and housing conditions (including Germ-free) and various mouse mutant strains we further explored the contribution of spontaneous and induced inflammatory signals in the generation, expansion and/or activation of Treg. This line of investigation has evidenced a robust feed back mechanism whereby maintenance, expansion and de novo generation of Tregs in adult is continuously adapted to the extent of inflammatory immune responses, whether directed at self or non-self components. The development of this project also drives us to further investigate the selective events involved in Treg development and pursue the analysis of the parameters conditioning Treg phenotype stability.

Funding

FCT-POCI, Portugal, SAU-MMO-58192/2004
Inflammatory components in the biology of regulatory T cells and the prevention of auto-immune disease

Collaborators

IGC, Oeiras
Disease Genetics Group - Carlos Penha Gonçalves
Inflammation Group - Miguel P. Soares

Research Project

Selection of Antigen specific TCR repertoire and T cells function

Less than 1% of T cell precursors survive the various developmental check-points that take place in the thymus. During these processes, TCR selection in the thymus ensures self-MHC restriction through positive selection and eliminate a large number of cells expressing TCR of high affinity/avidity for MHC-peptide complexes (negative selection) such that the actual TCR repertoire in the periphery approximate value of 107 (in mice). While conventional T cells repertoire is enriched by these selection events for the recognition of antigens yet to be encountered in the periphery, regulatory T cells repertoire appears to respond to different rules. These cells are activated intra-thymically through interaction with MHC-peptide, presumably expressed by cortical thymic epithelium TEC, and therefore encompass a TCR repertoire enriched in self-reactivities. During this selection process Tregs acquire expression of the transcription factor Foxp3 essential for their function. The FL group investigates the nature of the antigen presenting cells that drive Treg selection and the origin of the selecting antigen. This quest leads us to also investigate the antigen receptor repertoire requirements for immune tolerance establishment and maintenance.

Funding

FCT-POCI, Portugal-PTDC/SAU-MII/71402/2006
Quantitative and Qualitative T cell receptor repertoire requirements for immune tolerance establishment and maintenance

Collaborators

IGC, Oeiras
Quantitative Organism Biology Group - Jorge Carneiro

Research Project

B cell-T cell interaction for immune regulation

The intravenous administration of high doses of immunoglobulins pooled from the plasma of healthy donors (IVIg therapy) has beneficial effects in patients with a variety of autoimmune disorders including SLE. These clinical observations indicate that IVIg has potent anti-inflammatory characteristics, and identification of its precise mode of action may open up perspectives for future therapeutic strategies. Whether IvIg may be beneficial for SLE as a consequence of restoration of the Tregs pool or enhancement of their function has not been directly addressed. However, theoretical grounds for this hypothesis exist: i) animal deficient in B cells have reduced number of Tregs, ii) the inherent diversity of reactivities contained in IvIg is likely to encompass that of receptors expressed by Treg, iii) the effects of IvIg administration resemble in many aspect those monitored after adoptive transfer of Tregs (modification of endogenous Ig repertoire, general physiological equilibrium, inhibition of innate cell activity). We are approaching this issue by developing a longitudinal study in SLE patients and by performing reconstitution experiments in mice.

Funding

Sponsor research agreement, Octapharma, Portugal
ivIg therapy in SLE: Regulating the Regulators

Collaborators

IGC, Oeiras
Lupus and Autoreactive Immune Repertoires Group - Constantin Fesel

Publications

(selected) Updated Jan 2, (2009).

Santos, M. A., L. M. Sarmento, M. Rebelo, A. A. Doce, I. Maillard, A. Dumortier, H. Neves, F. Radtke, W. S. Pear, L. Parreira, and Demengeot, J. (2007). Notch1 engagement by Delta-like-1 promotes differentiation of B lymphocytes to antibody-secreting cells Proc Natl Acad Sci USA 104(39) :15454-115459

S. Zelenay, T. Lopes-Carvalho, I. Caramalho, M. F. Moraes-Fontes, M.l Rebelo and Demengeot, J. (2005). Foxp3+ CD25- CD4 T cells constitute a reservoir of committed regulatory cells that regain CD25 expression upon homeostatic expansion Proc Natl Acad Sci USA 102 :4091–4096

Braun, D., Geraldes, P. and Demengeot, J. (2003). Type I Interferon controls the onset and severity of autoimmune manifestations in lpr mice Journal of Autoimmunity 20 :15-25

Caramalho, I., Carvalho, T., Olster, D., Zelenay, S., Haury, M. and Demengeot, J. (2003). Regulatory T cells selectively express Toll Like Receptors and are activated by Lipopolysaccharide Journal of Experimental Medicine 197 :403-411

Hori, S., Haury, M., Coutinho, A. and Demengeot, J. (2002). Specificity requirements for selection and effector functions of CD25+4+ regulatory T cells in anti-myelin basic protein T cell receptor transgenic mice. Proceedings of the National Academy of Sciences 99 :8213-8218

Hori, S., Carvalho, T. and Demengeot, J. (2002). CD4+CD25+ T cells control CD4+ T cell expansion in the lung of mice infected by pneumocyctis Carinii. European Journal of Immunology 32 :1282-1291