Inflammatory plasma cell infiltration of the urinary bladder in the aging C57BL/Icrfa(t) mouse.

An age related increased cellularity in the lamina propria of the mouse bladder is described. The identified cell types involved are plasma cells, lymphocytes, and eosinophilic leukocytes, and probably represent an inflammatory plasma cell infiltration. Two rare unidentified cell types were also seen. The cause of the inflammatory reaction is unknown, but the failure to detect a causative microorganism suggests that it might be an autoimmune response, possibly related to the clinical condition of interstitial cystitis. From foci of increased cellularity, located in the close proximity of blood vessels, lymphocytes migrate to the urothelium which otherwise shows no ultrastructural changes with age.