Unit: Cytokines and Lymphoid Development

Director: DI SANTO James

Using a genetic approach in mice, our projects seek to better define the essential roles of γc-dependent cytokines and their receptors in lymphopoiesis, peripheral lymphoid homeostasis and during immune responses. We have developed an alymphoid mouse model 1) to study the genetic program which controls NK cell differentiation and 2) for xenotransplantation of human tissues. These projects have important implications for our understanding of normal and pathological immune responses.

1) Roles of common γc cytokines in lymphocyte development, differentiation and homeostasis (G. Masse, E. Corcuff, H. Decaluwe, M. Garcia-Ojeda, C. Vosshenrich, & J.P. Di Santo in collaboration with A. Cumano, P. Vieira, P. Bousso, G. Eberl)

Cytokines play essential and non-redundant roles in the survival, proliferation and differentiation of all lymphocytes subsets. Our interests have been focused on cytokines utilizing the common γ chain (γc) that include IL-2, -4, -7, -9, -15 and -21. We have used mouse models to dissect the individual roles of γc cytokines in T, B and NK cell development and homoestasis.

Our current projects include i) analysis of the role of thymic stromal cell derived lymphopoietin (TSLP) in early thymocyte development, ii) analysis of IL-7 as a survival and quiescence factor for naïve T cells, iii) defining the role for γc cytokines in effector T cell differentiation, and iv) characterizing the lymphocyte ‘niche' through dynamic imaging in vivo.

2) NK cell development and function (M. Hasan, O. Richard, N. Huntington, M. Garcia-Ojeda, C. Vosshenrich, & J.P. Di Santo)

Natural killer cells are an essential cellular component of the innate immune response and may help orient adaptive immunity following infection by pathogenic microorganisms. We have a long-standing interest in the genetic orchestration of NK cell development from hematopoietic stem cells. Using mouse mutants that target the transcriptional control mechanisms that specify lymphopoiesis, we aim to identify the key transcription factors that are responsible for NK cell lineage commitment and that maintain NK cell effector functions. The biological consequences of mutations that affect NK cell differentiation are assessed using the relevant in vivo infection and tumor models.

3) Immune response against spontaneous murine melanoma (S. Lesjean-Pottier, & C. Vosshenrich in collaboration with L. Larue, Institut Curie, and M. Giovannini, Cancéropole Ile-de-France).

Melanoma is the most lethal form of skin cancer and arises from malignant transformation of the pigment-producing melanocytes. Current treatment, including radio-, chemo-, and immuno-therapies, for this disease are rather inefficient. In order to improve immunotherapy for melanoma, we are studying the in situ immune response to spontaneously arising murine melanoma. These mouse models exhibit many clinical and pathological features of the human disease. Our approach involves non-invasive visualization of the different stages of melanoma development in order to study the anti-melanoma immune response in a temporal fashion.

Our objectives include i) analysis of innate and adaptive immunity against spontaneous melanoma in situ, ii) analysis of the contribution of the specific T cell response against melanoma: visualizing immunity against an engineered melanosomal antigen, iii) defining the cellular mechanisms of immunosurveillance against spontaneous melanoma, and iv) refining cellular therapy and prophylactic vaccination for the treatment of spontaneous melanoma.

4) The migration circuit of gut lymphocytes (D. Guy-Grand, J.P. Di Santo, with P. Vassalli, G. Eberl, F. Lemaitre)

We are continuing our research on the circulation of gut-associated lymphocytes. Intra-epithelial lymphocytes include conventional T cells (TCRαβ, CD4 or CD8αβ) and other T cells that are particular to the gut epithelium (TCRαβ CD8αα or TCRγ). It is known that mice that are defective in α4β7 expression have a strong reduction in gut-associated T cells. We have shown that the precursors of gut-associated T cells circulate as dividing cells in the thoracic duct lymph.

We are currently attempting to answer two main questions : i) Do precursors for gut-associated T cells express α4β7 ? If so, where do they acquire this adhesion molecule complex ? and ii) in euthymic mice, the four IEL types are derived from thymic precursors. In adult thymectomized mice, the number and percentage of IELs are not changed. Where are IEL precursors renewed under these conditions ?

5) Humanized mouse models (H. Strick-Marchand, O. Richard, E. Corcuff, & J.P. Di Santo in collaboration with F. Lemonnier, P. Charneau, GPH Stem Cells)

An alymphoid mouse strain harboring mutations in the Recombinase activating gene (Rag) and the γc chain has been developed for use in xenotransplantation of human tissues (Rag°γc° mice). We have successfully demonstrated that Rag°γc° mice can be engrafted with human hematopoietic stem cells, human myoblasts, or human hepatocytes. In these cases, long-term engraftment (up to 6 months) and in situ differentiation of human tissues can be achieved.

Our current projects include i) development of Rag°γc° mice carrying human HLA transgenes and human cytokines in order to maximize the efficiency of human HSC engraftment and subsequent T cell development in mice, ii) derivation of Rag°γc° mice carrying a non-revertant dystrophin allele for human muscle cell progenitor engraftment, and iii) development of a humanized mouse harboring both human lymphocytes and human hepatocytes for use in testing vaccines for protection against hepatitis C virus. This last project was selected for funding by the Bill and Melinda Gates Foundation in the context of the Grand Challenges in Global Health program.

Keywords: cytokines, development, immune response, mutation, tumor, infection

Activity Reports 2005 - Institut Pasteur

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