IL-12 p40 Homodimer-Dependent Macrophage Chemotaxis and Respiratory Viral Inflammation Are Mediated through IL-12 Receptor β1¹

Leukocyte recruitment to the airway lumen is a central feature of inflammatory conditions such as asthma and respiratory viral infection. Characterization of mediators that regulate leukocyte recruitment in these conditions revealed increased IL-12 p40 homodimer (p80) levels were associated with enhanced airway macrophage accumulation. To examine this association, we used in vivo and in vitro assays to demonstrate p80, but not IL-12 or p40, provided a macrophage chemoattractant signal. Macrophages from genetically deficient mice indicated p80-dependent chemotaxis was independent of IL-12 and required IL-12Rβ1 (Rβ1) expression. Furthermore, analysis of murine cell lines and primary culture macrophages revealed Rβ1 expression, with an intact cytoplasmic tail, was necessary and sufficient to mediate p80-dependent chemotaxis. To examine the role for Rβ1 in mediating macrophage accumulation in vivo, we contrasted Sendai virus-driven airway inflammation in wild-type and Rβ1-deficient mice. Despite similar viral burden and production of the macrophage chemoattractant p80, the Rβ1-deficient mice displayed a selective decrease in airway macrophage accumulation and resistance to viral-dependent mortality. Thus, Rβ1 mediates p80-dependent macrophage chemotaxis and inhibition of the p80-Rβ1 interaction may provide a novel anti- inflammatory strategy to manipulate the inflammation associated with asthma and respiratory viral infection.