FIG. 3.

Mature lymphocytes develop in the absence of p130 and p107. (A) Fetal thymocytes of p130^−/−;p107^−/− and control embryos at day 18 of gestation were subjected to flow cytometric analysis for expression of CD4 and CD8. Results are representative of at least two embryos of each genotype. FITC, fluorescein isothiocyanate. (B and C) The lymphoid compartments of Rag2^−/− animals were reconstituted via adoptive transfer of fetal liver from p130^−/−;p107^−/− and control embryos. After 6 weeks, the presence of mature B and T lymphocytes was assessed by flow cytometric analysis of B220 and Thy1.2 expression, respectively (B), and CD4 and CD8 expression (C) on splenocytes of reconstituted animals. Data are representative of three independent analyses, and the ratio of T to B lymphocytes in each was influenced by the time elapsed since reconstitution, as the B-cell lineage matures more rapidly than the T-cell lineage. Splenocytes of Rag2^−/− controls were devoid of mature lymphocytes, as expected (data not shown). (D) Thymocytes of animals reconstituted with p130^−/−;p107^−/− or control fetal liver exhibit similar levels of CD4⁺ CD8⁺ (double-positive) and CD4⁺ or CD8⁺ (single-positive) T cells.