Characterisation of mouse prothymocytes

In this thesis, the study of growth kinetics of thymocytes in lethally irradiated mice as a means to characterise the early T-cell progenitors is described. Normal bone marrow cells were used as the source of hemopoietic cells. The experiments show that it is possible to obtain information on T-cell differentiation from a complex experimental set-up in vivo. The quantitative relation between the thymus regeneration capacity and the CFU-S content of bone marrow cells was established. K"1netk studies of the regeneration process led to formulation of the framework for the lil vivo thymus regeneration assay (Chapter 3). From the study of erythroid and granulocyte-macrophage lineages, it had been established that at least these lineages start from early progenitor cells that are immediate successors of the pluripotent cells, but can be distinguished experimentally from CFU-S (Bol, 1980). However, apart from the cells postulated by Abramson et al. (1977), no such early progenitor cells are known for the T-cell 1"1neage. Our results obtained in thymus repopulation after transplantation of bone marrow from normal mke did not allow a distinction between the T-cell progenitor function of prothymocytes and that of the pluripotent stem cell determined as CFU-