Skeletal muscle regeneration is impaired by the absence of T cells.

<p>Muscle weight (A), cross-sectional area (CSA) of myofibers (B) and the number of satellite cells (C) are comparable in uninjured Rag2<sup>-/-</sup> γ-chain<sup>-/-</sup> (black bars) and C57Bl6 (WT, white bars) mice (n = 4 mice per group, mean ± SEM). (D) Representative images of skeletal muscle sections at day 15 after CTX. Centrally nucleated myofibers (new formed fibers) are shown (Red = Laminin; Blue = Hoechst). (E) At day 15 and 20 after injury, the CSA of myofibers is significantly lower in the absence of T lymphocytes (Rag2<sup>-/-</sup> γ-chain<sup>-/-</sup> mice, black bars) (n ≥ 2 mice per group, mean ± SEM). (F) Pax7 expression peaks at day 5 is blunted in Rag2<sup>-/-</sup> γ-chain<sup>-/-</sup> mice (black circles); the same mice did not show differences in the level of expression of Igf1 compared to WT mice (white circles) (n ≥ 2 mice per group, mean ± SEM; fold increase was calculated with reference to the untreated muscle, NT). (G) Rag2<sup>-/-</sup> γ-chain<sup>-/-</sup> mice (black circles) show a blunted expansion of satellite cells at 5 days after injury compared to WT mice (white circles) (n ≥ 3 mice per group, mean ± SEM; fold increase was calculated with reference to the untreated muscle of the corresponding genotype, NT).</p>