B220 expression by T lymphoid progenitor cells in mouse fetal liver

• Published in: The Journal of immunology (1950) Vol. 158; no. 2; pp. 666 - 676
• Main Authors: Sagara, S, Sugaya, K, Tokoro, Y, Tanaka, S, Takano, H, Kodama, H, Nakauchi, H, Takahama, Y
• Format: Journal Article
• Language: English
• Published: United States Am Assoc Immnol 15.01.1997
• Subjects: Animals; B-Lymphocytes - immunology; Embryonic and Fetal Development - immunology; Flow Cytometry; Hematopoietic Stem Cells - immunology; Hematopoietic Stem Cells - metabolism; Leukocyte Common Antigens - biosynthesis; Liver - cytology; Liver - immunology; Macrophages - immunology; Mice; Mice, Inbred C57BL; Mice, Transgenic; Receptors, Antigen, T-Cell, alpha-beta - biosynthesis; T-Lymphocytes - immunology; T-Lymphocytes - metabolism
• ISSN: 0022-1767; 1550-6606
• DOI: 10.4049/jimmunol.158.2.666

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.