Fig. 4
cTEC density increases with atrophy, indicating contraction of cell size without changing in number. a, b Wide area view of thymus from 5 week or 12-month-old mice (respectively) in which an H2b:mCherry fusion protein is conditionally activated in all cells of the TEC lineage. Images represent a maximum Z projection of an optical slice with thickness equal to the average feret diameter of one TEC nuclei (~11 µm). Paired images were acquired and processed identically. Regions indicated by dashed lines are shown in panels c and d. Consistent with this visual assessment and the contraction of cTEC projections by the Confetti reporter, measurement of TEC density shows that cTEC density increases dramatically with age, while mTEC density is not significantly changed (e and f, respectively; statistical significance calculated by two-tailed t test). Data indicate total nuclei per image volume from at least 3 independent thymuses of each type, with each thymus represented by one or more distinct image volumes until large numbers of nuclei were counted. Total events counted were 5060 (young cortex), 3567 (aged cortex), 17,097 (young medulla), or 10,176 (aged medulla). Boxes represent the interquartile range with the median indicated by a horizontal line; whiskers indicate the full range. Source data are provided in the accompanying Source Data File
