Drosophila macrophage-like cell lines with no functional peroxisomes, generated by RNA interference-mediated depletion of the peroxisome biogenesis factors (peroxins) Pex5 or Pex7 (designated as PEx5-i or Pex7-i, respectively), had an impaired ROS and RNS response to bacterial infection. The gene discussed is PEX5; the disease is bacterial infectious disease.