Activation of rat pulmonary lavage cells by intratracheal administration of polyinosinic-polycytidilic acid.

Systemic administration of biologic response modifiers (BRMs) is often limited by serious adverse effects. Local delivery of a BRM may provide a means to avoid systemic side effects while enhancing host defense. To test this hypothesis, the effects of intratracheal administration of the interferon inducer polyinosinic-polycytidilic acid (Poly-I:C) were examined. We demonstrated that intratracheal administration of Poly-I:C in rats results in alterations in pulmonary lavage cell number, population distribution, and function, suggestive of cellular activation. Following intratracheal instillation of 15, 75, or 150 mg of Poly-I:C, we observed a dose-dependent increase in Fc receptor-mediated phagocytosis, a dose-independent tumoricidal activity directed against xenogeneic P815 murine mastocytoma target cells, and a dose-independent decrease in superoxide anion (O2-) generation. With the exception of O2- generation, these functions returned to normal control levels by 7 days after a single dose of Poly-I:C. Thus, localized administration of Poly-I:C enhanced the host defense capability of pulmonary lavage cells, providing a rationale for compartmentalized immunoprophylaxis in the lung.