T-cell infiltration in RAPA-treated mdx muscles. Six wks following either local rapamycin (RAPA) microparticle (Rapa Bead) administration to the tibialis anterior (TA) muscle or systemic RAPA administration in drinking water (Rapa H2O) of mdx mice beginning at 6 wk of age, TA muscles were collected for analysis. Controls included untreated wild-type C57BL/10 muscle (B10) and mdx muscle from mice that were treated with blank beads (Blank Bead) or untreated. T-cell infiltration was evaluated by immunohistochemistry of TA muscle cross-sections to detect CD4+ and CD8+ effector T cells and Foxp3+ T regulatory cells. Muscle sections incubated with isotype control antibody (Iso) in place of the primary antibody serve as negative controls for immunohistochemistry. Data is presented as the average number of cells (± SE) per cross-section (A). Arrows in panel (B) indicate T-cell infiltrates. n = 5 for RAPA-treated and B10 groups and n = 4 for the blank bead and untreated group. *P < 0.05 and **P < 0.01.