Expression of muscle cell surface antigen 5.1H11 in infantile or juvenile spinal muscular atrophy

Monoclonal antibody 5.1H11 reacts with a cell surface antigen of human myoblasts and myotubes in cell culture. We found that levels of this antigen decrease to background levels during development of fetal muscle, and this down-regulation occurs after innervation. Adult myofibers are uniformly negative for 5.1H11 reactivity. Denervated muscle fibers from cases of Werdnig-Hoffmann disease and Kugelberg-Welander syndrome expressed 5.1H11 reactivity, while innervated fibers on the same sections were negative. Levels of 5.1H11 antigen therefore appear to be regulated by nerve in these spinal muscular atrophies.