Peritoneal cells (PC) in C57B1/6 (B6, H-2b) mice receiving an intraperitoneal (i.p.) injection of allogeneic BALB/c (H-2d) spleen cells demonstrated potent cytotoxic activity against syngeneic, xenogeneic, third-party allogeneic tumors as well as H-2d derived tumors. Maximum cytotoxic activity against various tumors other than H-2d derived tumor, B16 (H-2b) was elicited on day 3 post allosensitization and decreased drastically thereafter, whereas cytotoxic activity against P815 (H-2d ) peaked 3 days after the inoculation and maintained the peak activity thereafter. Surface phenotype of PC responsible for the cytotoxic activity against B16 was Thy-1 +/-, Lyt-2-, L3T4-, asialo GM1 (AGM1)+, and that of PC against P815 was Thy-1+, Lyt-2+ (or Lyt-2 +/-), L3T4-, AGM1+. These phenotypes showed similar phenotypes to the counterparts against B16 and against P815 in spleen cells induced by intravenous inoculation of alloantigen. When mice were pretreated i.p. with anti-AGM1 antibody before the allosensitization, anti-P815 cytotoxic activity in PC was completely diminished. Similar activity in spleen, however, was enhanced by i.v. treatment with the antibody before the i.v. inoculation of alloantigen. The data clearly demonstrate that in vivo inoculation of B6 mice with normal allogeneic cells induces "NK-like" CD8-cytotoxic cells and "anomalous" CD8+ cytotoxic cells in PC.It has been demonstrated that in vitro cultured lymphocytes in human and in murine system show cytotoxic activity against syngeneic cells as well as allogeneic cells without any apparent genetic restriction in relation to the sensitizing antigen / cells (7, 14, 17). These cytotoxic cells, namely anomalous killer (AK) cells (7, 17 ), emerge only when culture conditions contain an activating stimulus such as allogeneic lymphocytes (11). We have demonstrated that spleen cells from B6 mice that had been injected with normal BALB/c spleen cells via tail vein augmented killer activities against syngeneic B16 and allogeneic P815 tumor targets 3 days post in vivo alloantigen inoculation (11). Cold target inhibition assay revealed no or very little cross-competition between B16 and P815 in each cytotoxic activity. Surface phenotype of cytotoxic cells against B16 was Thy-1 + / -, Lyt-2-, AGM1+ and that 775
