Inability of antiserum active in antibody-dependent cellular cytotoxicity and arming tests to protect against simian virus 40 tumor cell challenge.

Previous studies have shown that simian virus 40 (SV40) hamster tumor cells that were pretreated with antiserum from syngeneic hosts sensitized to SV40 were killed following exposure to nonsensitized spleen cells. In this study preincubation of nonadherent spleen or lymph node cells with SV40 antiserum rendered the cells specifically cytotoxic for the SV40-transformed fibroblasts. The capacity of a particular antiserum to "arm" (i.e., to be made specifically cytotoxic) was comparable with its ability to mediate antibody-dependent cellular cytotoxicity (ADCC). Experiments were performed to determine if the SV40 antiserum had prophylactic activity. Two hours after passive transfer of serum, cytotoxic effector cells could be demonstrated in the blood, spleen, and mesenteric lymph node, and the recipients' sera were active in ADCC tests. Nevertheless, such hosts were not resistant to challenge with small numbers of SV40 tumor cells that were given intradermally or intracardiacly, nor was tumor growth suppressed by addition of normal lymph node cells to the antiserum-pretreated tumor cell inoculum. Thus SV40 antiserum, active at high titer in ADCC and arming assays, did not prevent or delay growth of SV40 tumor isografts.