Proposed role for small cytoplasmic vesicles in cytokine secretion by mouse macrophages.

This report represents an extension of a prior report hypothesizing that cytokines in mouse macrophages are secreted by a morphologic array of small vesicles which fuse with the cell membrane and which originate in the Golgi complex [Med Hypoth 53 (1999) 107]. The Golgi complex in macrophages is distinguished by a characteristically multicentric configuration and shows budding of vesicles from the closely approximated tips of the lamellae. The location of small vesicles which extend from the Golgi complex to the cell membrane supports the hypothesis that there is one type of vesicle which fuses with the cell membrane and secretes its content of cytokines. The other type of vesicle has been shown to fuse with pinocytic vacuoles to form hydrolase positive cytoplasmic granules. Consideration of cytokines produced by macrophages will help to clarify the immunologic functions of these cells.