The expression of differentiated functions in somatic cell hybrids: retention and activation of C3 production.

Rat and mouse fibroblasts which do not secrete the third component of complement (or secrete it at a very low rate), were respectively hybridized with mouse and rat hepatoma cells which actively produce C3. These interspecific hybrids actively secrete both mouse and rat C3. The production of C3 coded by the hepatoma cell genome is thus retained, but in addition, the secretion of C3 coded by the fibroblast genome is activated. On the other hand, intraspecific hybrids have been isolated from normal diploid C3 producing cells and non-producing cells. These cell hybrids also retain the capacity to secret C3. Retention of C3 production thus does not appear to be peculiar to hybrides derived from hepatoma cells.