Importance of the concomitant presence of palpable MOPC-315 tumor in stimulation of splenocytes by C-type MOPC-315 virus in vitro.

BALB/c mice inoculated with MOPC-315 tumor cells developed an antiviral response against C-type particles extracted from subcutaneous tumors of plasmacytoma-bearing mice as shown by in vitro stimulation of spleen cells from tumor-bearing mice by virus-containing preparations. Induction of blastogenic response by virus-containing preparations was found to occur in unfractionated spleen cell populations, the glass-wool non-adherent fraction (depleted of macrophages and tumor cells) and the nylon-wool non-adherent (T-enriched) fraction of spleen cells. The antiviral response was no more detectable in spleens of tumor-bearing mice cured by melphalan. Cured mice developed a strong antitumor immune response as shown by their resistance to challenge with a tumorigenic dose of MOPC-315 tumor cells. However, challenge with tumor cells of cured, resistant mice did not induce reappearance of antiviral response.