Reaction of the vesical wall to bacterial penetration: resistance to attachment, desquamation, and leukocytic activity.

To determine the contribution of the bladder wall to defense against infection we designed a series of experiments wherein movement of introduced bacteria and inflammatory processes (cystitis) were observed by autoradiographic technique. As a first defense line, the bladder mucosal surface showed strong resistance against bacterial attachment and penetration. Moreover, epithelial cells gripped and penetrated by bacteria were desquamated and eliminated through voiding, thus arresting deeper invasion into the bladder wall. When organisms did penetrate the bladder wall, they were phagocytized by polymorphonuclear leukocytes and macrophages in the submucosa and muscularis. In contrast, once leukocytes had migrated into the urine within the bladder, they no longer participated in phagocytosis. Organisms also entered the veins, or the lymphatics, or both, and disappeared rapidly from the local site through the action of the reticuloendothelial system. These observations indicate that--in addition to mechanical emptying--resistance to bacterial attachment, desquamation of invaded cells, activity of leukocytes and macrophages, and disappearance of bacteria from local site are four mechanisms whereby the bladder resists and fights infection.