IFNG and nutritional deficiency disease: Under various adverse growth environments, such as cytokine stimulation (e.g. interferon-gamma (IFN-γ)), antibiotic use (e.g. penicillin), nutritional deficiency (e.g. amino, acid, glucose, and iron deprivation), heat shock, phage infection, and viral co‐infection [47,61], developing Chlamydia may enter a viable but non-cultivable persistence state in stress response (variously termed aberrant bodies(ABs), persistent bodies, or chlamydial stress response), which is conducive to the immune escape of the pathogen.