CD4+ and CD8+ T cells have also been associated with muscle degeneration and fibrosis in the mdx mice, a natural mutant that does not express dystrophin and Duchenne muscular dystrophy (DMD) homolog, by induction of specific antigen activation of CD44+ cells homing into the damaged tissue [26,27,28]. The gene discussed is CD4; the disease is Duchenne muscular dystrophy.