The role of cytostasis in antitumor immunity: comparison between syngeneic and allogeneic systems

Concomitant immunity against tumor development is enhanced by the oral administration of a kampo medicine, Hochu-ekki-to (TJ-41: Bu-Zhong-Yi-Qi-Tang)

The oral administration of a kampo herbal medicine, Hochu-ekki-to (TJ-41: Bu-Zhong-Yi-Qi-Tang) using a water-supplying bottle resulted in a slight but significant inhibition of Meth A growth. The oral administration of TJ-41 with gastric gavage significantly enhanced the specific antitumor activity against Meth A at rechallenge on day 9. In a tumor-neutralizing assay, the tumor draining LN cells of the TJ-41 administered mice showed an antitumor activity against Meth A. In a cytolytic assay, the anti-Meth A specific cytolytic T lymphocyte activity was not detected in the spleen cells of the Meth A bearing and TJ-41 administered mice. The oral administration of TJ-41 enhanced the natural killer (NK) activity of the spleen cells in naive mice but could not improve the decreased NK activity of spleen cells from the tumor bearing mice. In a cytostatic assay, the peritoneal exudate cells from the Meth A bearing and TJ-41 administered mice showed a significantly higher amount of cytostatic activity against Meth A than that from either Meth A bearing or TJ-41 administered mice. These results indicate that the oral administration of TJ-41 into the tumor bearing mice may thus be able to enhance concomitant antitumor immunity through the augmentation of the cytostatic activity.

Th1 type CD4+ T cells may be a potent effector against poorly immunogenic syngeneic tumors

We examined the possibility that Th1 type CD4+ T cells may be an effector against three kinds of syngeneic tumors such as highly immunogenic B16 melanoma (B16) and two poorly immunogenic lines of MCA fibrosarcoma (MCA) and 3LL carcinoma (3LL). In a proliferation assay, the Th1 type CD4+ T cell clone (MH2) recognized the purified protein derivatives (PPD) derived from Mycobacterium tuberculosis. In a tumor-neutralizing assay, MH2 showed anti-tumor activity against both B16 and MCA. In a model of pulmonary metastasis, MH2 also showed anti-tumor activity against both B16 and 3LL. In an assay of cytolysis, MH2 showed a moderate level of tumor necrosis factor-dependent cytolytic activity only against MCA. In a cytostasis assay, MH2 showed a high level of interferon gamma-dependent cytostatic activity against the three tumors in the presence of macrophages. The anti-tumor activity of MH2 against B16 and 3LL was suggested to be, at least in part, attributable to the augmented natural killer activity. Taken together, these findings suggest that we may potentially be able to utilize Th1 type CD4+ T cells as an effector for immunotherapy against poorly immunogenic tumors.

Early appearance and activation of natural killer cells in tumor-infiltrating lymphoid cells during tumor development

We investigated NK cell infiltration into tumor developing lesions at early stage of tumor development after intraperitoneal inoculation of 3LL lung carcinoma into syngeneic C57BL/6 mice. Natural killer (NK) cells, which were detected by anti-NK 1.1 monoclonal antibody (mAb), remarkably increased in number in tumor-developing lesions (peritoneal cavity) as early as day 3 after inoculation of 3LL. The tumor-infiltrating NK cells from 3LL-inoculated mice produced a high level of interferon-gamma by co-culture with 3LL and showed enhanced cytotoxic activities against both NK-sensitive (YAC-1) and NK-resistant (3LL and P815) tumors. Furthermore, mice depleted of NK cells by injection of anti-NK 1.1 mAb or anti-asialo GM1 antibody showed shorter survival times after intraperitoneal inoculation of 3LL when compared with control mice. These results suggest that NK cells infiltrate the tumor-developing lesion at an early stage and may participate in the early protection against tumors through production of a high amount of interferon-gamma and enhanced cytotoxicity at tumor-bearing sites.

Evidence for involvement of TNF-alpha in the induction phase and IFN-beta in the effector phase of antiproliferative activity of splenic macrophages

Splenic macrophages play a key role in regulating cell proliferation during a variety of chronic perturbations of the hematopoietic system. This regulatory activity is in sharp contrast to the activities of inflammatory monocytes/macrophages in that it is not dominated by the secretion of prostaglandins or toxic metabolites such as peroxides. A productive model for studying these nontoxic regulatory activities of splenic macrophages has been provided by macrophages generated in vitro (M phi-c) during autologous spleen cell culture. The M phi-c effectively inhibit (greater than 90%) lymphocyte proliferation by inhibiting G1----S phase progression without inhibiting the production of interleukins by the lymphocytes. Conditioned medium from M phi-c activated with LPS + rIFN-gamma effected a similar G1 arrest of activated lymphocytes. The involvement of IFN-beta in effecting the antiproliferative activity is suggested by (1) the ability of monospecific anti-IFN-beta mAB, but not anti-TGF-beta, anti-IL-1, anti-TNF-alpha, or anti-IFN-gamma, to neutralize the antiproliferative activity in the M phi-c supernatants and (2) the ability of purified IFN-beta to effect a similar inhibition of cell proliferation (i.e., G1 arrest without inhibition of interleukin production). rTNF-alpha and rIFN-gamma could not effect such an inhibition of cell proliferation and did not synergize with IFN-beta in producing such an antiproliferative effect. The M phi-c could be activated to effector function by a combination of LPS + rIFN-gamma or rTNF-alpha + rIFN-gamma, but not by any one of those reagents alone. LPS alone was sufficient to stimulate TNF-alpha production by the M phi-c. Activation of the M phi-c by LPS + rIFN-gamma could be completely blocked by anti-TNF-alpha antibodies. These data suggest that the M phi-c can be induced to produce inhibitory levels of cytostatic cytokines by a TNF-alpha autocrine loop that is IFN-gamma dependent. The in vivo relevance of this effector mechanism is suggested by, and discussed in the context of, the recent reports of "spontaneous" production of IFN-beta during immunological disorders.

Ambient level ozone effects on subpopulations of thymocytes and spleen T lymphocytes

The effects of ozone on thymocyte and spleen T lymphocyte subpopulations were studied. Balb/c mice were exposed to clean air or to 0.3 +/- 0.05 ppm ozone for 1-3 wk. Thymocytes and spleen T cells were stained with fluorochrome conjugated monoclonal antibodies against surface differentiation markers and/or propidium iodide for deoxyribonucleic acid (DNA). The cells were then analyzed by fluorescence activated cell sorter. The percentages of certain thymocyte and spleen T lymphocyte subtypes and DNA synthesizing spleen T cells were lower following 1 wk of ozone exposure. After 3 wk exposure, the thymocyte percentages were higher in ozone-exposed mice, whereas the absolute number remained lower, and spleen T lymphocytes showed no changes. The findings suggest that short-term ozone inhalation can affect the T cell immune system adversely, particularly the CD4+ cells.

Oral administration of Chlorella vulgaris augments concomitant antitumor immunity

Chlorella vulgaris, an unicellular green algae, or its acetone-extract (Ac-Ex) were administered orally to Meth A tumor bearing BALB/c or (BALB/c x DBA/2)F1 (CDF1) mice. When CDF1 mice were fed daily with 10% dried powder of Chlorella vulgaris (CVP) containing diet before and after Meth A tumor inoculation, the growth of rechallenged Meth A tumor was significantly suppressed in an antigen-specific manner. Augmentation of antitumor resistance was exhibited also by Winn assay using lymph node cells of tumor-bearing mice orally administered with CVP or Ac-Ex. Antigen-specific concomitant immunity in these mice were mediated by cytostatic T cells but not by cytotoxic T cells. Natural killer cells seemed not to contribute in antitumor resistance in this system.

Immunological mechanisms of antitumor activity of some kinds of Chinese herbs: Meth A-induced delayed type hypersensitivity

In the present paper, we confirmed that a delayed type hypersensitivity response can be elicited against Meth A tumor (Meth A-DTH) in BALB/c mice bearing the primary tumor. This response was augmented by lipopolysaccharide. We examined the effects of 4 kinds of Chinese herbs including A. capillaris, S. doederleinii, A. macrocephala and S. subprostrata on the Meth A-DTH, and the results were compared with that of the herbs on picryl chloride-induced delayed type hypersensitivity (PC-DTH). All of the herbs examined augmented the Meth A-DTH 10 days after the primary tumor transplantation, and S. doederleinii, A. macrocephala and S. subprostrata prevented the decay of the response on the 20th day, but A. capillaris did not. On the other hand, none of the herbs affected the PC-DTH. When both DTH responses were caused simultaneously in the same mouse, Meth A-DTH decayed 20 days after the transplantation but PC-DTH did not. In this case, the effects of these 4 herbs on Meth A-DTH and PC-DTH were essentially the same as those seen in the case of separate experiments. The previous and present results suggest that A. capillaris shows antitumor activity mainly through a direct cytotoxicity, although this herb might have certain components to enhance Meth A-DTH, and the other herbs display the activity through the enhancement of T cell-mediated tumor immunity, particularly tumor specific DTH.

Increased capacity of lymphocytes to lyse tumor cells in vitro and production of lymphotoxins after cisplatin treatment

Spleen lymphocytes from C3H/He mice when treated with cisplatin show increased cytostasis and cytotoxicity against Dalton's lymphoma cells in vitro. Cisplatin treatment of splenocytes does not render them cytotoxic/or cytostatic against normal splenocytes. Splenocytes on treatment with cisplatin also produce tumor cell-specific cytotoxic/cytostatic factors (lymphotoxins) which have cytolytic and cytostatic effect on Dalton's lymphoma cells. The increased cytotoxicity of splenocytes on treatment with cisplatin is reversed by the calcium channel blocker nifedipine and the calmodulin antagonist chlorpromazine, suggesting a role of calcium in cisplatin-activated lymphocyte-mediated cytotoxicity.

Antigen-specific augmentation of delayed-type hypersensitivity by immune serum factor in mice: augmentation of anti-tumor cytostatic activity

A humoral factor capable of augmenting delayed-type hypersensitivity antigen specificity (DAF) is present in the serum of mice sensitized with heterologous erythrocytes to induce a delayed footpad reaction (DFR). In the present study, a similar factor was identified when xenogeneic tumor cells were used as antigens. This factor also could augment the in vitro anti-tumor cytostatic activity against homologous tumor cells, which correlated with in vivo DFR to the same tumor cells. The cytostatic activity augmented by the transfer of this factor had the following characteristics: The activity appeared in the whole peritoneal exudate cells (PEC) from serum recipients at 4 days after the antigenic challenge. Such an activity was revealed in the collaboration of plastic dish-nonadherent and -adherent PEC as the primary and final effectors, respectively. The appearance of primary effector cells for such an activity was also accelerated in spleen and lymph node cells. However, a sufficient number of macrophages were always required as the final effectors in their functional expression. These primary effectors were sensitized T lymphocytes which produced lymphokine(s) such as macrophage-activating factor(s) and which contributed to this augmented cytostatic activity through the activation of macrophages. Thus, this immune serum factor seems to exert functional expression by accelerating the generation of lymphokine-producing delayed-type T lymphocytes, which is also responsible for cytostatic anti-tumor immunity.