Transtracheal administration of interleukin-12 induces neutrophil responses in the murine lung

Although the roles of interleukin-12 (IL-12) in the immunomodulation of ant igen-specific responses are well characterized, the effects of IL-12 on the respiratory tract following mucosal administration are not well defined. T herefore, we investigated changes in the murine lung shortly after intranas al (i.n.) administration of murine IL-12. We showed that IL-12 induced neut rophil influx to the murine lung in both C57BL16 and BALB/c mice. Histologi c examination revealed that intranasal administration of HL-12 with liposom es induced focal neutrophil infiltration into the alveoli and a significant increase in neutrophils in bronchoalveolar lavage fluids when compared wit h administration of liposomes alone. In vitro chemotaxis assays indicated t hat the observed pulmonary neutrophil response induced by IL-12 could have been due in part to the direct chemotactic activity of IL-12 for murine neu trophils.