Transient antigen-specific non-reactivity of an organ induced in sensitized animals by repeated challenges. A new experimental phenomenon observed in the parotid gland of rats.

Acute sialoadenitis, ascribed to local formation of immune complexes, develops in sensitized rats after a single intraductal challenge with the sensitizing antigen. Multiple intraductal challenges induce a state of non-reactivity of the organ characterized by a lack of inflammatory reaction to the sensitizing antigen. This non-reactivity is antigen-specific, since introduction of ovalbumin, after multiple intraductal instillations of bovine serum albumin (BSA), elicits an inflammatory response in animals immunized with the two antigens. At the same time, instillation of BSA into the contralateral gland, which has not been challenged, causes acute adenitis. Anti-BSA antibodies are detected in the serum and parotid saliva at the time of refractoriness of the gland. The phenomenon is a transient one since the faculty of the salivary gland to respond by an inflammatory reaction recovers after a challenge-free period. These experiments bring to light a new phenomenon, the possible mechanisms of which are discussed.