title: B220 expression by T lymphoid progenitor cells in mouse fetal liver.
abstract: The present study has characterized T lymphoid progenitor cells that reside in mouse fetal liver. Day 14 fetal liver contains progenitor cells that can differentiate into mature T cells upon being transferred into the thymus by hanging drop cultures. Fractionation of fetal liver cells indicated that T progenitor cells were confined in TER119- CD45+ FcR(low) cells. To our surprise, B220+ rather than B220- fraction in TER119- CD45+ FcR(low) fetal liver cells exhibited efficient progenitor activity generating T cells. Progenitor activity by the B220+ fetal liver cells was restricted to T cells, B cells, and macrophages at frequency approximately 1/10, approximately 1/10, and approximately 1/20, respectively, of isolated B220+ cells. B220+ fetal liver cells did not contain detectable D-J rearrangement of TCR-beta gene and were c-kit+ IL-7R+ Thy-1- CD3- CD4(low) CD8- CD25- CD44+. B220+ fetal liver cells expressed mRNAs encoding TCR-beta, pT alpha, Ig alpha, and VpreB. Interestingly, TCR beta-chains were expressed by B220+ fetal liver cells in the VDJ-rearranged TCR-beta-transgenic mice, indicating that TCR-beta transcription and B220 expression are activated simultaneously by the transgenic B220+ fetal liver cells. These results indicate that B220 is expressed by fetal liver lymphoid progenitor cells that can become T cells, and suggest that lymphoid progenitor cells in fetal liver concurrently undergo T- and B-specific molecular events within a single cell.
authors.affiliation: Department of Immunology, Institute of Basic Medical Sciences, University of Tsukuba, Japan.
authors.forename: S
authors.initials: S
authors.lastname: Sagara
authors.forename: K
authors.initials: K
authors.lastname: Sugaya
authors.forename: Y
authors.initials: Y
authors.lastname: Tokoro
authors.forename: S
authors.initials: S
authors.lastname: Tanaka
authors.forename: H
authors.initials: H
authors.lastname: Takano
authors.forename: H
authors.initials: H
authors.lastname: Kodama
authors.forename: H
authors.initials: H
authors.lastname: Nakauchi
authors.forename: Y
authors.initials: Y
authors.lastname: Takahama
mesh_terms: D000818:Animals; D001402:B-Lymphocytes / Q000276:immunology; D005314:Embryonic and Fetal Development / Q000276:immunology*; D005434:Flow Cytometry; D006412:Hematopoietic Stem Cells / Q000276:immunology* / Q000378:metabolism*; D017493:Leukocyte Common Antigens / Q000096:biosynthesis*; D008099:Liver / Q000166:cytology* / Q000276:immunology*; D008264:Macrophages / Q000276:immunology; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D016693:Receptors, Antigen, T-Cell, alpha-beta / Q000096:biosynthesis; D013601:T-Lymphocytes / Q000276:immunology* / Q000378:metabolism*
chemical_list: D016693:Receptors, Antigen, T-Cell, alpha-beta; D017493:Leukocyte Common Antigens