Transplantation of Embryonic Spleen

Mice were housed in a specific pathogen-free facility and all animal experiments were carried out in accordance with approved protocols of the Tokyo University of Science Animal Care and Use Committee. Tlx1^{CreER-Venus/+} mice have been described previously^{22 (link)}. Rosa26^tdTomato mice (purchased from The Jackson Laboratories) were maintained on a C57BL/6 background. Tamoxifen (0.1 g/kg body weight; Sigma-Aldrich, St Louis, MO) was delivered by intragastric gavage to induce activation of CreER. Transplantation of the embryonic spleen under the kidney capsule of adult mice was carried out as previously described^{40 (link)}. Unless otherwise indicated, littermates were used as controls; genotypes and treatments are indicated in the text or figure legends.