Selective deletion of mature peripheral V beta 2+ T-cells was observed in BALB/c mice implanted with the syngeneic C4 preneoplastic hyperplastic alveolar nodule (HAN) but not in mice with sham surgery (W. Z. Wei, R. Ficsor-Jacobs, S. J. Tsai, and R. Pauley, Cancer Res., 51:3331-3333, 1991). We now report the participation of host cells in that process. Peripheral V beta 2+ T-cells were reduced by 50% or more 4 weeks after an i.v. injection of 10 x 10(6) spleen cells from C4 HAN-bearing mice. Both T- and B-cell-enriched splenocytes mediated V beta 2 deletion. Secondary adoptive transfer of splenocytes from the recipients of the primary adoptive transfer also resulted in V beta 2+ T-cell deletion. The splenocytes lose V beta 2-deleting activity after 500 rad irradiation. V beta 2 deletion induced by either C4 HAN or splenocytes was more profound in CD4+ than in CD8+ T-cells. Loss of V beta 2+CD4+ T-cells was observed 5 days after the adoptive transfer of splenocytes, whereas V beta 2+ CD8+ cells were not reduced until day 9 or later. The differential rate of V beta 2+ CD4+ and CD8+ T-cell reduction continued for at least 7 weeks after the adoptive transfer. The pattern of V beta 2 deletion and the sequence of T-cell loss is similar in the recipients of C4 HAN or of adoptively transferred splenocytes. Southern blot analysis demonstrates non-germ line Mtv or MMTV proviral DNA in C4 HAN. Splenocytes of C4 HAN-bearing mice express a higher level of 1.7-kilobase long terminal repeat transcript than normal BALB/c splenocytes, suggesting a role for a unique Mtv/MMTV provirus in V beta 2 deletion.