Effect of serum from mice with dormant Friend leukemia viral infections on synthesis and modulation of erythroleukemia cell surface gp70.

Serum of mice with dormant Friend virus infections modulates the expression of cell surface antigens on Friend virus-transformed cells (FLC-745 cells). By radioimmunoassay, the modulated antigen was identified as virion gp70 of Friend leukemia virus. After two days of culture in medium containing 5% serum from mice with dormant Friend virus infections, the modulated cells expressed about 50% less surface gp70 than non-modulated cells cultured in 5% normal mouse serum. After 9 days in culture, the modulated cells expressed no surface gp70; however, these cells contained the same amount of internal gp70 as nonmodulated cells, indicating that gp70 was synthesized during the modulation period. Both modulated and nonmodulated cells grew equally well during the 9 days of culture. These results indicate that the effects of modulation of Friend virus-coded cell surface antigens are restricted to the cell surface.