title: Distinct kinetic responses in vivo of cortical thymocytes of ageing mice to primary as compared to secondary peripheral antigenic stimulation.
abstract: 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.
mesh_terms: 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
chemical_list: D013745:Tetanus Toxoid; D004247:DNA