Consistently, day 10 post-infection lung extracts from these mice failed to promote GPR183+ cell migration, in contrast to extracts from Ch25hfl/fl mice (Fig. 2H), arguing that macrophages are the principal driver of GPR183 dependent chemotaxis by providing 25-HC that is converted into 7α,25-HC in the lung during infection. The gene discussed is GPR183; the disease is infection.