CD45⁺ cells, including T cells, infiltrate skeletal muscle after CTX injury.

(A) Percentages of CD45+ cells in skeletal muscle at different time points after CTX injury (n ≥ 3 mice analyzed per time point, mean ± SEM). (B) The number of CD45+ cells in skeletal muscle peaks at day 3 and rapidly decreases thereafter (n ≥ 3 mice per time point, mean ± SEM). (C) The percentage of T cells (red) among muscle-infiltrating CD45+ cells increase with time, passing from a few cells present at day 1 (12 ± 3%, mean ± SD) to 25 ± 7% (mean ± SD) at day 3, and 37 ± 7% and 34 ± 7% (mean ± SD) at day 5 and 7 respectively (n ≥ 4 mice analyzed per time point). (D) The number of CD45+ and CD3+ cells present in muscle at different time points after injury. CD3+ cells increase in number after day 3, remain constant until day 5, and decline by day 7 (n ≥ 3 mice per time point, mean ± SEM).