Repopulation of the mouse thymus after sublethal fission neutron irradiation. I. Sequential appearance of thymocyte subpopulations
Huiskamp, R.; van Ewijk, W.
Journal of Immunology 134(4): 2161-2169
1985
ISSN/ISBN: 0022-1767 PMID: 2857747 Document Number: 243041
The T cell composition of the thymus of sublethal fission neutron-irradiated CBA/H mice was analyzed with cytofluorometry and immunohistology, using monoclonal antibodies directed to the cell surface antigens Thy-1, T-200, MT-4, Lyt-1, Lyt-2 and MEL-14. The results of this investigation show that whole body irradiation with 2.5 Gy fission neutrons results in a severe reduction and degeneration of the cortex, the medulla is affected to a lesser extent. Irradiation selects, within 24 h, for a population of dull Thy-1+, bright T-200+, bright Lyt-1+ cells localized in the medulla. Phenotype analysis of the generation of the thymus, which starts at .apprx. 5 days after irradiation, reveals the sequential appearance of: null cells, i.e., lymphoblasts negative for all tested antigens, mainly in the subcapsular area but also in the medulla; Thy-1+ only and T-200+ only cells in the subcapsular area; 3 Thy-1+, T-200+ cells; and Thy-1+, T-200+, MT-4+, Lyt+ cells in the cortex. An increased MEL-14 expression is observed in correlation with the expression of Thy-1 and T-200 determinants during the regeneration of the thymus. From day 10 on up to at least 150 days after irradiation, no differences can be observed in the thymus of irradiated and age-matched sham-irradiated control mice, as measured by the expression and distribution of Thy-1, T-200, MT-4, Lyt-1, Lyt-2 and MEL-14 antigens. The observed sequence in phenotype shift in the regeneration of the thymus after irradiation is discussed in view of recently published data on the differentiation of the T cell system.