Development of the immune system in severe combined immunodeficiency mice reconstituted with transferred fetal liver cells.

Severe combined immunodeficiency (SCID) mice were immunologically reconstituted by the transfer of fetal liver cells (FLC) from BALB/c (SCID-isoFLC mice) or C57BL/6 mice (SCID-alloFLC mice). The developmental process of the immune system in the peripheral blood (PB) was almost comparable between SCID-isoFLC and SCID-isoFLC mice. Analysis of the lymphoid organs and the PB from SCID-alloFLC mice indicated that slg+ B cells appeared and were distributed to the periphery within 2 weeks after the transfer of FLC. It was also suggested that precursor T cells entered the thymus before 4 weeks after the transfer, and were differentiated into mature CD4+ or CD8+ T cells which then migrated to the periphery by 6 weeks. All of mature lymphocytes in the periphery of the SCID-alloFLC mice were shown to express donor-type H-2 antigens. Additionally, in the SCID-isoFLC mice, cell-mediated immunity such as rejection against alloantigens was functioning from 6 weeks, and humoral immune function was suggested by the detection of cells generating antigen-specific antibodies. We discuss that development of the immune system in SCID mice receiving transferred FLC was comparable to that normally seen in the fetal and neonatal stages.