Macrophages (M phi s) undergo a physiological response known as the macrophage disappearance reaction (MDR) in response to certain stimuli in the peritoneal compartment. The types of stimuli that can cause the MDR, the relationship of the MDR to the host immunological response, and the possible role of the MDR in M phi activation are reviewed. The data indicate that the MDR occurs in response to both acute nonspecific inflammatory and specific immune delayed hypersensitivity processes and that the MDR may play an important role in M phi activation.

No abstract

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.

No abstract