Suppression of in vitro maintenance and interferon-mediated augmentation of natural killer cell activity by adherent peritoneal cells from normal mice

The ability of adherent peritoneal cells (APC) to inhibit murine natural killer (NK) cell activity was examined. Nylon wool-nonadherent splenic effector cells were incubated overnight with or without different numbers of APC. NK activity was then measured against YAC-1 in a 4-hr 51Cr-release cytotoxicity assay. Proteose peptone-elicited or unstimulated resident APC from normal mice markedly suppressed NK activity of splenic effector cells in the presence or absence of exogenously added interferon. The suppression was dependent on the number of APC added with 10% APC, relative to the number of effector cells, resulting in a greater than 65% inhibition of cytotoxicity. The effector phase of cytotoxicity was not the target of the suppressor cells, because APC did not suppress NK activity when they were present only during the cytotoxicity assay. The addition of APC to alloimmune cytotoxic T cells under similar conditions resulted in no inhibition of cytotoxicity. Both syngeneic and allogeneic APC suppressed NK activity, but several murine macrophage-like cell lines lacked this property. In contrast to APC, incubation of effector cells with adherent spleen cells from normal mice resulted in no inhibition of NK activity. APC from mice injected with C. parvum were less inhibitory for NK activity than normal resident APC. In contrast, C. parvum APC suppressed concanavalin A-induced lymphoproliferation and were directly cytotoxic to tumor target cells in vitro, whereas normal APC lacked these properties. The results indicate that the peritoneum of untreated mice contains suppressor cells that can inhibit the in vitro maintenance and IFN-mediated augmentation of NK activity. In addition, these results indicate a broader spectrum of immune reactivities regulated by APC and suggest that, depending on their level of activation, APC can preferentially inhibit different immune functions

Induction of immunotoxicity by polycyclic hydrocarbons : role of the Ah locus

We have employed the plaque forming cell (PFC) response to sheep erythrocytes as well as lymphocyte proliferation to study the induction of immunotoxicity in AHH-inducible (Ah Locus positive, C57BL/6N; B6C3F1) and AHH non-inducible (Ah Locus negative, DBA2/N) mice following administration of polycyclic aromatic hydrocarbons. When two potent carcinogenic polycyclic hydrocarbons which induce AHH activity, 3-methylcholanthrene (MCA) or 1,2,5,6-dibenzanthracene [DB(a,h)A] were administered IP, immunotoxicity was observed in both AHH-inducible and AHH non-inducible animals. However, the AHH-inducible animals appeared to be more sensitive, and substantial suppression of a PFC response toxicity could be induced with doses as low as 14 mg/kg methylcholanthrene. While suppression of a mitogen response required a dose of 43-125 mg/kg. Administration of the weak carcinogen 1,2,3,4-dibenzanthracene [DB(a,c)A], IP, which similarly induces AHH activity in inducible animals, failed to induce immunotoxicity in either C57B1/6N or DBA/2N mice. In contrast to the results obtained following IP administration, when MCA was administered repeatedly (4X) via an intragastric (IG) route we observed striking immunosuppression of a PFC response in Ah locus negative (DBA/2) animals but minimal effects in Ah locus positive animals (C57B1/6). We finally observed that a single IP dose of MCA (125 mg/kg) to Ah locus positive animals substantially inhibited Natural Killer Cell activity but had more limited effects on the ability of an animal to reject a challenge by an immunogenic syngeneic fibrosarcoma

Antitumor efficacy of adenocarcinoma cells engineered to produce interleukin 12 (IL-12) or other cytokines compared with exogenous IL-12

BACKGROUND: Numerous animal model studies have examined the ability of genetically engineered tumor cells to release cytokines and to elicit an immune memory against the parental tumor. Often only a single cytokine is studied, and few comparative studies have been conducted. PURPOSE: We evaluated the antitumor efficacy of adenocarcinoma cells engineered to release interleukin (IL)-12 in a mouse model system. The efficacy of this cytokine was compared with that of other cytokines released by engineered adenocarcinoma cells and that of exogenous IL-12 administered both locally and intraperitoneally. METHODS: BALB/cAnCr mice were inoculated with syngeneic parental mammary adenocarcinoma (TSA) cells in quantities sufficient to lead to tumors in all inoculated mice. TSA cells engineered to release IL-12 (TSA-IL12) were also injected into normal and selectively immunosuppressed BALB/cAnCr mice. Tumor incidence, growth, and rejection patterns were evaluated by the measurement of neoplastic masses and by the study of the histologic and ultrastructural features of the tumor site. The effects of local or intraperitoneal administration of recombinant IL-12 (rIL-12) on tumor-bearing animals were also studied. RESULTS: Most mice rejected TSA-IL12 cells through a CD8-positive, T-lymphocyte-dependent reaction associated with macrophage infiltration, vessel damage, and necrosis. The systemic immunity of mice that had rejected TSA-IL12 cells to a subsequent challenge with parental TSA cells was less efficient than that elicited by TSA cells engineered to release IL-4 or IL-10 but equivalent to that elicited by TSA cells engineered to release IL-2, IL-7, and interferon alfa. Compared with TSA cells engineered to produce other cytokines, TSA-IL12 cells were the most efficient in curing mice with established TSA tumors; injection of 0.1 million proliferating cells contralaterally to the tumor growth area cured five of 15 mice bearing 1-day-old tumors; injection of the same dose of proliferating cells into the tumor growth area cured two of 20 tumor-bearing mice. However, two 5-day courses with a nontoxic dose (0.1 microgram) of rIL-12 given intraperitoneally cured a similar proportion of these animals (six of 20). Only two of 20 mice with 7-day-old TSA tumors were cured by vaccination with proliferating TSA-IL12 cells, whereas 24 of 30 mice with such tumors were cured by intraperitoneal administration of rIL-12. CONCLUSIONS: TSA cells engineered to release IL-12 are rejected by most mice; the ensuing immune memory for TSA parental cells, however, was less efficient than that elicited by proliferating TSA cells engineered to release other cytokines (e.g., IL-4, IL-10, and possibly interferon gamma). The immune reaction elicited by TSA-IL12 cells was the most efficient in curing mice with established TSA tumors; notably though, the same or a better cure rate was obtained with rIL-12 given intraperitoneall