It has recently been demonstrated that in vivo administration of murine interleukin 12 (IL-12) to mice results in augmentation of cytotoxic natural killer (NK)/lymphocyte-activated killer cell activity, enhancement of cytolytic T cell generation, and induction of interferon gamma secretion. In this study, the in vivo activity of murine IL-12 against a number of murine tumors has been evaluated. Experimental pulmonary metastases or subcutaneous growth of the B16F10 melanoma were markedly reduced in mice treated intraperitoneally with IL-12, resulting in an increase in survival time. The therapeutic effectiveness of IL-12 was dose dependent and treatment of subcutaneous tumors could be initiated up to 14 d after injection of tumor cells. Likewise, established experimental hepatic metastases and established subcutaneous M5076 reticulum cell sarcoma and Renca renal cell adenocarcinoma tumors were effectively treated by IL-12 at doses which resulted in no gross toxicity. Local peritumoral injection of IL-12 into established subcutaneous Renca tumors resulted in regression and complete disappearance of these tumors. IL-12 was as effective in NK cell-deficient beige mice or in mice depleted of NK cell activity by treatment with antiasialo GM1, suggesting that NK cells are not the primary cell type mediating the antitumor effects of this cytokine. However, the efficacy of IL-12 was greatly reduced in nude mice suggesting the involvement of T cells. Furthermore, depletion of CD8+ but not CD4+ T cells significantly reduced the efficacy of IL-12. These results demonstrate that IL-12 has potent in vivo antitumor and antimetastatic effects against murine tumors and demonstrate as well the critical role of CD8+ T cells in mediating the antitumor effects against subcutaneous tumors.

Interleukin 12 (IL-12) is a heterodimeric cytokine with a number of biological effects that are consistent with its potential role as an antitumor agent. The antimetastatic and antitumor activities of IL-12 have been demonstrated in a number of murine tumor models. Both the inhibition of established experimental pulmonary or hepatic metastases and a reduction in spontaneous metastases have been achieved by treatment with murine IL-12. Systemic treatment of mice bearing subcutaneous tumors with IL-12 results in tumor growth inhibition, prolongation of survival, and, in some models, tumor regression. The antitumor effect of IL-12 in these models is dose-dependent and can be initiated against well-established tumors. Mice cured of their tumor by IL-12 treatment are specifically immune to rechallenge with the same tumor. A series of experiments have demonstrated that both T-cells and interferon-gamma (IFN-gamma) induction are necessary for the optimal antitumor effects of IL-12. However, the antitumor efficacy of IL-12 has not been observed after exogenous administration of murine IFN-gamma, suggesting that additional factors may be important for the antitumor effects of IL-12. In several tumor models, IL-12 is more active or has a larger therapeutic window than either IL-2 or IFN-alpha, two cytokines with demonstrated antitumor activity against human malignancies. Combining IL-12 with other cytokines or chemotherapeutic drugs can improve antitumor effects.

Clinical and laboratory studies were carried out to compare the antibacterial properties of two antiseptic mouthwashes, namely 1% povidone iodine and 0.2% chlorhexidine gluconate. In a group of 10 subjects after a single rinse with povidone iodine, an immediate mean fall in total salivary aerobes and anaerobes occurred, followed by a return to normal levels by 1-hour postrinsing. With chlorhexidine gluconate a similar but greater reduction in salivary bacterial counts was observed, which was still present up to the 7-h postrinsing period. Saliva samples obtained from the subjects 2 min after rinsing with providone iodine produced little or no inhibition to the growth of a test organism in vitro, whereas following chlorhexidine gluconate, antibacterial activity was present in the saliva specimens up to the 3-h sampling time. Using culture media containing comparable levels of soluble protein to saliva, the minimum inhibitory concentrations of povidone iodine against several standard test organisms were much higher than those of chlorhexidine gluconate. The results suggest that povidone iodine, as a mouthwash, exerts only an immediate antibacterial effect and unlike chlorhexidine, is not retained at antibacterial levels within the oral cavity after expectoration. This lack of prolonged action of povidone iodine in the oral cavity would appear to be relevant to its reported lack of antiplaque activity.

Continuous alveolar macrophage (AM) and tumor-infiltrated (TIM) cell lines have been generated from C57B16J mice by in vitro infection with the J2 retrovirus carrying the v-raf and v-myc oncogens. Four cloned AM cell lines (AMJ2-C8, AMJ2-C10, AMJ2-C11, AMJ2-C20) and 3 cloned TIM cell lines (TIMJ2-C4, TIMJ2-C7 and TIMJ2-C15) were expanded for further characterization. Flow cytometry detected the product of the raf gene in the cytoplasm of all these cell lines. Studies on the tumoricidal properties of these AM and TIM cell lines demonstrated differences in their response to a panel of known macrophage activators. Four of these cell lines (AMJ2-C8, AMJ2-C10, TIMJ2-C7 and TIMJ2-C15) were activated following exposure to recombinant murine interferon gamma (rMuIFN-gamma) but not lipopolysaccharide (LPS) or muramyl dipeptide (MDP). AMJ2-C20 was only activated by incubation with rMuIFN-gamma plus LPS. AMJ2-C11 and TIMJ2-C4 are the cell lines that most closely resembled the response pattern of the parental AM and TIM, since they could be activated by either the combination of rMuIFN-gamma plus LPS or rMuIFN-gamma plus MDP. Constitutive expression of MHC-class-II antigens was low on AMJ2-C11 or TIMJ2-C4 but was increased following exposure to rMuIFN-gamma. Neither cell line secreted substantial amounts of IL-1 or TNF but both secreted large amounts of IL-6. Thus these cell lines could be powerful tools to study AM and TIM activation and cytotoxicity.

Human chromosome 6 encodes both the interferon gamma receptor as well as the class I major histocompatibility complex antigens, HLA-A, -B, and -C. However, the presence of chromosome 6 in somatic cell hybrids is insufficient to confer sensitivity to human interferon gamma (Hu-IFN-gamma) as assayed by class I HLA induction; it is necessary for both human chromosomes 6 and 21 to reside in the hybrid to generate a response to Hu-IFN-gamma. Treatment of such a hamster-human hybrid, Q72-18, with Hu-IFN-gamma induces the class I HLA antigens. Q72-18 cells selected by fluorescence-activated cell sorting for the loss of class I HLA induction also lost human chromosome 21. Fusions of such cells to a hybrid that contains only human chromosome 21 reconstitutes HLA antigen induction by Hu-IFN-gamma. Furthermore, fusions of hybrids containing a translocated human chromosome 6q and the HLA-B7 gene to a line containing only human chromosome 21 or a translocated 21q also reconstitutes HLA-B7 mRNA and antigen induction by Hu-IFN-gamma. Thus the segregation of cells on the basis of a biological effect by fluorescence-activated cell sorting and reconstitution by hybrid fusion provides a strategy by which some biological pathways can be mapped at a chromosomal level.