Cellular repopulation and recovery of the phytogemagglutinine (PHA) responding cell pool in the thymus of sublethally irradiated mice.
Cellular repopulation and recovery of PHA reactivity was investigated in the thymus of mice exposed to 400 R either on the whole body or with one leg protected. In the whole body irradiated cases both the cellular repopulation and the restoration of PHA reactivity in the thymus showed a cyclic pattern: an initial depression and a subsequent first recovery being followed by a secondary cellular depletion and decrease of reactivity before another recovery phase started. The phase of the secondary decrease lasted fo a similar period for both the cell number and reactivity, but was shifted in time and the reduction in reactivity began some 12 days later than that in the cell number. In the leg-shielded animals, the cellular repopulation progressed without cyclic changes, but the recovery of PHA reactivity maintained a cyclic pattern. However, due to a smaller secondary decrease, it was less pronounced than in the whole body irradiated cases. During the aging of mice from 50 to 90 day old, the cell number in the involuting thymus decreased to half of the original. The decrease in the cell population was associated with an about four-fold increase of PHA reactivity. The results were discussed in regard to the origin of the immunoreactive thymic cells. Arguments were presented in favour of the hypothesis that both the reactive and nonreactive cells originate from precursors in common, but require different lengths of time for maturation.
D000375:Aging; D000818:Animals; D002452:Cell Count; D002477:Cells / Q000187:drug effects*; D037102:Lectins / Q000494:pharmacology*; D008297:Male; D051379:Mice; D011830:Radiation Effects; D013950:Thymus Gland / Q000473:pathology / Q000528:radiation effects*; D013997:Time Factors
D037102:Lectins