Cell growth and differentiation in vitro in mouse macrophages transformed by a tsA mutant of simian virus 40. III. Large T antigen level and cell proliferation and survival in an SV40 tsA640-transformed macrophage line

The levels of simian virus 40 (SV40) large T antigen in a tsA-transformed mouse macrophage line at the permissive (33°C) and the nonpermissive (30°C) temperature were examined by immunofluorescence, sodium dodecylsulfate-polyacrylamide gel electrophoresis, complement fixation, and enzyme-linked immunosorbent assay. When the cells were confluent and rested at 33°C, and then were shifted to 39°C, the amount of large T antigen per cell decreased, and most cells survived and remained phagocytic. When the cells were proliferating at 33°C, and then were shifted to 39°C, the cells died with only a small reduction in the amount of large T antigen. Therefore, the physiological state of the cells may determine the survival of cells by affecting the level of large T antigen after exposure to 39°C. The confluent cells may be rested with a concomitant decrease of large T antigen. The proliferating cells may not survive in the presence of a relatively high level of functionally defective large T antigen at 39°C.