To determine whether increased susceptibility to Pseudomonas infection in c3a.1−/− larvae is due to neutrophil-intrinsic activity, we crossed the c3a.1-deficient line to the Tg(mpx:mcherry-2A-rac2D57N) line, in which mcherry-labeled neutrophils express a dominant negative form of Rac2 and are thus rendered migration-deficient. The gene discussed is C3; the disease is Pseudomonas infection.