Renata I. Mazzucchelli 1 , Søren Warming 2 , Scott M. Lawrence 3 , Masaru Ishii 4 , Mehrnoosh Abshari 3 , A. Valance Washington 5 , Lionel Feigenbaum 3 , Andrew C. Warner 3 , Davis J. Sims 3 , Wen Qing Li 1 , Julie A. Hixon 1 , Daniel H. D. Gray 6 , Benjamin E. Rich 7 , Matthew Morrow 8 , Miriam R. Anver 3 , James Cherry 9 , Dieter Naf 3 , Lawrence R. Sternberg 3 , Daniel W. McVicar 5 , Andrew G. Farr 10 , Ronald N. Germain 4 , Keith Rogers 3 , Nancy A. Jenkins 2 , Neal G. Copeland 2 , Scott K. Durum 1 , *
10 November 2009
Interleukin-7 (IL-7) is required for lymphocyte development and homeostasis although the actual sites of IL-7 production have never been clearly identified. We produced a bacterial artificial chromosome (BAC) transgenic mouse expressing ECFP in the Il7 locus. The construct lacked a signal peptide and ECFP (enhanced cyan fluorescent protein ) accumulated inside IL-7-producing stromal cells in thoracic thymus, cervical thymus and bone marrow. In thymus, an extensive reticular network of IL-7-containing processes extended from cortical and medullary epithelial cells, closely contacting thymocytes. Central memory CD8 T cells, which require IL-7 and home to bone marrow, physically associated with IL-7-producing cells as we demonstrate by intravital imaging.