Given their adaptive capacity in response to infection and their role in combatting pathogens, we addressed the time points of their initial emergence as well as their postnatal development from first exposure to environmental microbiota (i.e., birth) to adulthood, utilizing ChAT-eGFP reporter mice and focusing upon tracheal, urethral, and, to a lesser extent, thymic CCC. Here, CHAT is linked to infection.