Fig. 6

Skeletal muscle IL-15 contributes to the progression of autoimmune myositis. a The expression of Il15 mRNA in various tissues of wt (n = 3), Il15 ^f/f (n = 5), and ACTA-Il15 ^−/− (n = 5) mice was detected by qPCR. WAT white adipose tissue. Data are mean ± SEM. ***p < 0.001. b The amount of IL-15/IL-15Rα complex protein in the serum of Il15 ^f/f and ACTA-Il15 ^−/− mice (n = 9–10) was measured by ELISA. Data are mean ± SEM. c Comparison of memory CD8⁺ T cell (mCD8) and NK cell (NK) level in the peripheral blood among wt, Il15 ^−/−, Il15 ^f/f, and ACTA-Il15 ^−/− mice (n = 5 in each group). Fold change was calculated by normalizing the percentage of indicated cell type in mutant mice to that in wt mice. mCD8 were H57⁺CD19⁻CD8⁺CD44^hiCD122^hi, and NK were H57⁻CD19⁻NK1.1⁺. Data are mean ± SEM. ***p < 0.001. d Mononuclear cell infiltration in the quadriceps muscles of Syt7 ^−/− Il15 ^f/f and Syt7 ^−/− ACTA-Il15 ^−/− mice 14 days after C protein immunization (Left). Mononuclear cell infiltration was found in the endomysium (black square), perimysium (black arrowhead), and perivascular region (white arrowhead). Focal lymphatic invasion of myofibers were observed in C-protein-immunized Syt7 ^−/− ACTA-Il15 ^−/− mice as indicated by the white arrowhead (Middle). The histopathology scores were compiled in the right panel with each symbol representing one mouse (Right). Scale bar in left = 100 μm; middle = 25 μm. **p < 0.01. e Expression of mononuclear cell markers, Cd4, Cd8, and F4/80, mRNA in the quadriceps muscles of C-protein-immunized mice measured by qPCR. Each symbol representing one mouse. *p < 0.05, **p < 0.01. f Expression of immune-relevant genes mRNA in the quadriceps muscles of C-protein-immunized mice measured by qPCR. Each symbol representing one mouse. *p < 0.05, **p < 0.01