Antigen Fluctuation and Virus Activation in EL 4 Cells Transplanted in Hybrid Mice or Cultured In Vitro 2

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Abstract
Because normal C3Hf (C3) mouse serum was previously demonstrated to contain natural antilymphoma antibodies (NAA's) that reacted with EL 4 lymphoma cells grown in syngeneic C57BL/6J (B6) mice found devoid of NAA's, we investigated the in vivo interaction between NAA's and their cell membrane receptors by transferring the EL 4 lymphoma in the NAA-positive (B6 × C3)F1 or NAA-negative (B6 × BALB/c)F1 offspring. The amount of NAA receptors, studied by direct cytotoxicity assay, absorption, and immunoelectronmicroscopy, was found to decrease when the lymphoma was grown in the NAA-positive but not in the NAA-negative hybrids. A simultaneous decrease in H-2 antigens and an active production of C-type virus particles were observed. The phenomena were reversible: When the EL 4 cells were retransferred in the parental NAA-negative B6 strain, the expression of both NAA receptors and histocompatibility antigens was fully recovered and the virus production dropped to the original low level. EL 4 cells cultured in vitro showed a similar decrease in expression of NAA receptors and H-2 antigens and a concomitant increase in C-type virus production. The increased virus production, which took place in either immune responsive hybrids or in vitro-cultured cells, was thought to be responsible for the observed antigenic variations.