Immunodeficient mice (NSG, NOD SCID, NOG) developing opportunistic infections or dying unexpectedly due to inadequate barrier housing.

Resolve pathogen risks and protect compromised lines: 1) House in dedicated immunodeficient rooms in the cleanest part of the facility using individually ventilated cages (IVCs) or microisolator cages. 2) Sterilize all materials, including caging, feed, bedding, and enrichment devices, via autoclaving or irradiation. 3) Perform all cage changes inside a Class II laminar flow hood or HEPA-filtered change station. 4) Handle immunodeficient animals first before handling immunocompetent ones. 5) Provide supplemental hydration gel during the 5-12 day acclimation period. Do not use prophylactic antibiotics, which can cause dysbiosis.