International Immunology Advance Access originally published online on May 19, 2009
International Immunology 2009 21(6):715-725; doi:10.1093/intimm/dxp043
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Loss of the pro-apoptotic BH3-only Bcl-2 family member Bim sustains B lymphopoiesis in the absence of IL-7
1 Cytokines and Lymphoid Development Unit, Institut Pasteur, 25 rue du Docteur Roux, 75724 Paris, France
2 Inserm U668, Paris, France
3 Division of Developmental Immunology, Department of Biocenter, Innsbruck Medical University, Innsbruck, Austria
4 Lymphocyte Development Unit, Institut Pasteur, Paris, France
5 Molecular Genetics of Cancer Division, The Walter and Eliza Hall Institute of Medical Research, Melbourne, Victoria 3050, Australia
Correspondence to: N. L. Alves; E-mail: nalves{at}pasteur.fr
IL-7 is pivotal for B cell development. Proteins of the Bcl-2 family are essential regulators of lymphocyte survival. Particularly, the pro-apoptotic BH3-only members Bim and Puma mediate lymphocyte apoptosis provoked by cytokine deprivation. Herein, we addressed whether the absence of Bim or Puma within the hematopoietic compartment could bypass the requirement for IL-7-driven B cell development in adult mice. We found that deficiency of Bim, but not Puma, partially rescued B cell development in the absence of IL-7. The numbers of both sIgM– and sIgM+ B cells were markedly increased in the bone marrow of recipients lacking IL-7 upon reconstitution with Bim-deficient hematopoietic progenitors, compared with their control or Puma-deficient counterparts. The augmentation of B cell lymphopoiesis in the absence of Bim was reflected in the mature peripheral compartment by an increase in both the number of immature and mature B cells in the spleen and in the circulating IgM levels. Bim-deficient B cells were also increased in IL-7-sufficient recipients suggesting that peripheral B cells homeostasis is governed by a Bim-dependent and IL-7-independent mechanism. Our data highlight the role of Bim as a key regulator of cell survival during B lymphocyte development in vivo.
Keywords: Bim, B lymphopoiesis, IL-7, Puma
Transmitting editor: D. Tarlinton
Received 12 January 2009, accepted 13 April 2009.
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