MURINE T-CELL HYBRIDOMA-DERIVED PRODUCTS REGULATE THE GROWTH OF SKELETAL-MUSCLE MYOBLASTS

We have analyzed the effects of T cell products on the growth of murine myoblasts. Supernatants from some T cell hybridomas were shown to have either growth factor activity or growth inhibitory activity on two myoblast lines raised in our laboratory from two different strains of mice and also on the C2C12 myoblast line. The hybridoma-derived growth factor activity was shown not to require cofactors contained in serum as its effects could be demonstrated in assays done in serum-free media. Further studies on the effects of purified lymphokines on myoblasts using recombinant IL-2, IL-3, IL-4, IL-6, and GM-CSF showed these lymphokines not to have any growth stimulatory activity indicating that factor(s) other than the ones tested may be operative. Characterization by dialysis and column chromatography of hybridoma supernatants revealed the presence of a low-molecular-weight inhibitor and a higher-molecular-weight growth factor that was found in several hybridoma supernatants.