After an i.p. transplantation of an allogeneic tumor (Meth A) to C57BL/6 mice, a macrophage (MO)-rich, non-T, non-NK cell population is induced as the major infiltrate and cytotoxic cells. We here evaluated the role of the MOs in the rejection of allografted Meth A cells and characterized the MOs in comparison with other well-known MOs. At all time intervals after transplantation, the highest cytotoxic activities against Meth A tumor were obtained with the MO-rich population. In addition, the lymphocyte-rich population had a significant but low cytotoxic activity, whereas two other population types, granulocytes and large granular cells, were inactive. When the MO-rich or the T cell-depleted MO-rich population was i.p. transplanted simultaneously with Meth A cells into untreated C57BL/6 mice, the tumor cells were rejected without growth. After specific elimination of MOs by in vivo application of dichloromethylene diphosphonate-containing liposomes, the cytotoxic activity against Meth A cells was hardly induced at the transplantation site of Meth A cells and the allografted Meth A tumor continued to grow, indicating that a type of MO is the effector cell essential for the rejection. In contrast to other well-known MOs, the cytotoxic activity against Meth A cells was cell-to-cell contact dependent and soluble factor (e.g., NO and TNFa) independent. Moreover, the cytotoxic activity of the MOs (H-r) against 'Cr-labeled Meth A (H-2d) cells was inhibited by the addition of unlabeled H-2d, but not H-2a, H-2k or H-2", lymphoblasts as well as Meth A cells, implying the specific interaction of the MOs with H-2d cells.

It has been reported that the rejection of tumor allografts is mainly mediated by cytotoxic T lymphocytes (CTLs). Here, we characterized the cytotoxic effector cells of C57BL/6 (B6; H‐2b) mice infiltrating into the rejection site of the i.p. allografted Meth A fibrosarcoma (or P815 mastocytoma) cells of H‐2d origin. Two types of cytotoxic cells (i.e., CD8+ CTLs and macrophages (Mφs)) were identified by flow cytometric fractionation of the infiltrates or by specific in vitro elimination of cells either with antibody (Ab)‐coated beads or with an Ab‐plus complement. Of particular interest, these effector cells showed distinct and unique target specificities. First, the CTLs were inactive against transplanted tumor (e.g., Meth A) cells, whereas they were cytotoxic against donor‐related concanavalin A (Con A) blasts as well as CTLL‐2 (H‐2b) cells transfected with a class I gene of H‐2d origin. A cold target competition assay suggested that the CTLs were composed of multiple sets of T cells, each of which specifically recognized different allo‐antigens. Second, the Mφs lysed the allografted tumor cells but were inert toward the Con A blasts and the CTLL‐2 transfectants. Unexpectedly, the infiltration of Mφs preceded the infiltration of CTLs by several days during the course of rejection. These results indicate that two distinct populations of unique cytotoxic cells (i.e., CTLs and Mφs) are induced in the allografted tumor rejection site, and that the infiltration of cytotoxic Mφs responsible for rejection precedes that of the CTLs cytotoxic against cells expressing donor‐related allo‐antigens.

Saikosaponin d, isolated from the roots of Bulpleurum falcatum L. was investigated for both its inactivating effects on some viruses and its antiviral effects against the viruses in vitro. Saikosaponin d at a concentration of more than 5 microM had direct inactivating effects on both measles virus and herpes simplex virus after incubation of the viruses with the agent for more than 10 min at room temperature. In contrast, exposure of poliovirus to even 500 microM of saikosaponin d resulted in no loss of infectivity, while the same concentration of saikosaponin d induced complete loss of infectivity in both measles virus and herpes virus. In addition, saikosaponin d was ineffective against the replication of measles virus, herpes virus, and polio virus at a concentration of 0.1 microM, whereas saikosaponin d did not induce an inhibitory effect on the growth of Vero cells, when Vero cells were treated with saikosaponin d 24 h before the inoculation (pretreatment) and immediately or 24 h after the infection of the viruses (post-treatment).

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The effects of saikosaponin-d (ssd), isolated from Bupleurum radix, on phagocytic functions of mouse peritoneal macrophages were investigated after treatment in vitro. The macrophages treated with ssd showed a significant increase in PMA-induced chemiluminescence. An increase in phagocytosis was detected after treatment with saikosaponin-b2 (0.1 microM) for 24 h in vitro, while a suppression of phagocytosis was observed following treatment with saikosaponins (0.5 microM). Treatment with ssd markedly increased the random migration of resident peritoneal macrophages, but did not affect the migration towards FMLP. We further investigated the effect of ssd on proliferative responses of spleen cells and found that ssd, which itself has no mitogenic activity, decreased spleen cell proliferative response to T-cell mitogen, but increased the response to B-cell mitogen.