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Articles by P Chambon
Total Records ( 2 ) for P Chambon
  E Shimura , N Hozumi , O Kanagawa , D Metzger , P Chambon , F Radtke , S Hirose and N. Nakano

Hyperplasia associated with a loss of tissue homeostasis can induce DNA replication stress, leading to precancerous dysregulation. Epidermal T cells reside in the primary barrier that protects against diverse environmental insults; however, the functions of these T cells in tissue surveillance are not completely understood. In mice with inducible Notch1 inactivation in keratinocytes that causes epidermal hyperplasia, epidermal T cells sensed stressed keratinocytes and migrated into the cutaneous draining lymph nodes. Simultaneous induction of β-galactosidase (β-Gal) as a putative antigen expressed in the process of precancerous dysregulation and Notch1 ablation in the epidermis resulted in elevated β-Gal-specific IgG2a production. Epidermal T cells were found to have the capacity to express chemokine (C-C motif) receptor 7 and migrate into the lymph nodes. Cutaneous draining lymph node cells in Notch1-inactivated mice expressed high levels of IFN- upon anti-CD3 plus anti-CD28 stimulation. Furthermore, induced expression of β-Gal in mice that lacked epidermal T cells failed to induce anti-β-Gal IgG. These results suggest that epidermal T cells play an essential role in the initiation process of epidermal antigen-specific humoral immune responses and demonstrate the importance of epidermal T cells in sensing precancerous dysregulation and activating adaptive immunity.

  L Chorro , A Sarde , M Li , K. J Woollard , P Chambon , B Malissen , A Kissenpfennig , J. B Barbaroux , R Groves and F. Geissmann

Most tissues develop from stem cells and precursors that undergo differentiation as their proliferative potential decreases. Mature differentiated cells rarely proliferate and are replaced at the end of their life by new cells derived from precursors. Langerhans cells (LCs) of the epidermis, although of myeloid origin, were shown to renew in tissues independently from the bone marrow, suggesting the existence of a dermal or epidermal progenitor. We investigated the mechanisms involved in LC development and homeostasis. We observed that a single wave of LC precursors was recruited in the epidermis of mice around embryonic day 18 and acquired a dendritic morphology, major histocompatibility complex II, CD11c, and langerin expression immediately after birth. Langerin+ cells then undergo a massive burst of proliferation between postnatal day 2 (P2) and P7, expanding their numbers by 10–20-fold. After the first week of life, we observed low-level proliferation of langerin+ cells within the epidermis. However, in a mouse model of atopic dermatitis (AD), a keratinocyte signal triggered increased epidermal LC proliferation. Similar findings were observed in epidermis from human patients with AD. Therefore, proliferation of differentiated resident cells represents an alternative pathway for development in the newborn, homeostasis, and expansion in adults of selected myeloid cell populations such as LCs. This mechanism may be relevant in locations where leukocyte trafficking is limited.

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