Anti-rabbit thymus actin antibody inhibits proliferation of Epstein-Barr virus-transformed human B cell line LA350: Augmentation by cyclic AMP

Antibody to actin isolated from the rabbit thymus gland exerted a dose-dependent inhibitory effect upon the proliferation of an Epstein-Barr virus-transformed human B cell line, LA350. Purified rabbit thymus actin specifically reversed the inhibitory effect of antibody by competing with surface actin on LA350. For example, LA350 proliferation at 48 hr was inhibited 90% at a 1:10 antibody dilution (p < 0.001) but only 48% and 20% in the presence of 190 and 380 μg/ml of rabbit thymus actin, respectively (p < 0.001 for reversal). Cyclic AMP augmented in a dose-related fashion the inhibitory effects of antibody, e.g., a 1:20 dilution of antibody inhibited 10, 19, 41, and 67% at 0.0, 0.5, 1.0, and 2.0 m M cAMP, respectively (p < 0.001). We conclude that anti-actin antibody recognizes surface actin on a human B cell line and produces a functional inhibition of proliferation by a process that is augmented by cAMP.