Distinct kinetic responses in vivo of cortical thymocytes of ageing mice to primary as compared to secondary peripheral antigenic stimulation.
We have studied cellular kinetic changes in the thymic cortex of ageing mice as a function of time after primary and secondary stimulation with aluminum phosphate adsorbed tetanus toxoid via the hind leg footpads. Absolute numbers of DNA synthesizing cortical thymocytes per cross-section of the thymus were computed from combined data obtained by planimetry, counts of cell density (cellularity) and assessment of the labelling index, 1 h after injection of (methyl-3H)-thymidine. The proliferative activity of these cells in the outer fourth of the thymic cortex reached a peak exceeding significantly control values by 45% 14 days after primary, but not secondary, peripheral antigenic stimulation. We conclude that the cortical thymocyte population responded in a distinct manner to the first immunization as opposed to the booster injection of the same antigen.
D000375:Aging; D000818:Animals; D002452:Cell Count; D002455:Cell Division; D004247:DNA / Q000096:biosynthesis; D005260:Female; D007117:Immunization, Secondary; D007700:Kinetics; D051379:Mice; D013601:T-Lymphocytes / Q000276:immunology* / Q000378:metabolism; D013745:Tetanus Toxoid / Q000276:immunology*; D013950:Thymus Gland / Q000166:cytology*; D013997:Time Factors
D013745:Tetanus Toxoid; D004247:DNA