The lymphocyte uropod: a specialized surface site for immunologic recognition.

Abstract

Functional specialization of the cell surface of motile protozoa such as the Paramecium and amoeba are generally recognized (Ambrose and Forrester, 1968; Wolpert and Gin-gell, 1968). Less well appreciated is the existence of differentiated surface membranes on mammalian leukocytes. In this laboratory we have been interested in a modification of the lymphocyte surface called the uropod, an area consisting of microvillus projections of cell membrane adjacent to the golgi-associated cell pole. The cytoplasm contained in the uropod is rich in microtubules, mitochondria, endoplasmic reticulum, and numerous endocytic vesicles, and is quite distinct from the pseudopod region which contains few such subcellular organelles. Moreover, the uropod is not engaged in cell motility as is the pseudopod. The lymphocyte surface membrane functions in immunologic recognition, cell cooperation, and cell-mediated cytotoxicity in an as yet undefined manner. Circumstantial evidence suggests that the uropod may represent the site of such interactions.