Inhibition of replication of virus-transformed fibroblasts by antibodies to RNA.

The activity of 7S immunoglobulins (Ig) antibody to RNA, obtained in rabbits after a prolonged immunization with RNA-methylated bovine serum albumin complex was evaluated in vitro on normal (3T3) and simian virus 40-transformed (SV 3T3) mouse fibroblasts. The presence of anti-RNA antibody in the culture medium inhibited both the SV 3T3 cell proliferation and the [3H]thymidine incorporation. In contrast, an increased [3H]uridine incorporation was evident within 48 and 96 hr of culture. No significant modification in these 3 parameters was observed in 3T3 cultures treated in the same manner. Both 3T3 and SV 3T3 showed cytoplasmic fluorescence when cultured in the presence of fluoresceinated anti-RNA Ig. However, with the indirect fluorescence technique anti-RNA Ig were detected in SV 3T3 cytoplasm only. These data suggest that anti-RNA Ig were taken up by both 3T3 and SV 3T3, but only in SV 3T3 did the anti-RNA Ig retain their antigenic properties and block cellular proliferation.