Fig. 2.

The ontogeny of primary lymphopoietic activity in fetal liver (A), bone marrow (B) and thymus (C). The proportions of putative lymphoid progenitors (CD45^loCD172a⁻ cells, solid line) and mature lymphocytes (CD45^hiCD172a⁻ cells, dotted line) in fetal liver (A) and bone marrow (B) demonstrate the shift of lymphopoietic activity between these hematopoietic centers. The thymus (C) is populated by pro-T cell progenitors from the same hematopoietic centers that can be easily observed by two waves of developing immature DP precursors (large CD4⁺CD8⁺ cells that are CD3⁻TCRαβ⁻TCRγδ⁻, dashed line). Relationship to the development of mature αβ (small CD3^hiTCRαβ⁺ cells, solid line) and γδ (small CD3^hiTCRγδ⁺ cells, dotted line) T lymphocytes in the thymus is also shown. The ontogeny of occurrence for peripheral mature αβ T cells (solid line), γδ T cells (dotted line) and B cells (dashed line) is shown for fetal blood (D) and spleen (E). Data are based on results previously published by Sinkora et al. [8], [10], [14], [33], [43].