[Reaction of different cell populations in mouse thymus to a single gamma-irradiation]

Cytoarchitectonics of the functional zones of thymus was studied with the morphometric technique. Reactions of different cell populations to a single gamma-irradiation at a dose of 6.9 Gy were demonstrated. Acute reaction in thymus showed up already on the first day following exposure. Reparation began three days later and proceeded in two stages one of which (day 7) was accomplished by survived cells and the other (day 21), owing to the influx of precursors from recovered bone marrow. It was found that thymic substantia medullaris was less compromised by radiation as compared with cortex. This was due to the presence of more resistant lymphoid cells and activation of lymphocytopoiesis proper. It was also established that in the post-irradiation period (days 1 through to 58) cytoarchitectonics of the thymic functional zones has failed to complete recovery. Moreover, a second thymus depletion was observed on day 58.