C bodies and R bodies in the epithelial cells of normal and diseased human rectum.

Small spherical, extracellular bodies (C bodies) measuring 20 to 80 nm in diameter and enclosed by a trilaminar membrane 7 nm wide surrounded the microvilli of human rectal epithelial cells. Similar bodies were observed within membrane-bound vesicles (R bodies) in the apical cytoplasm. The C bodies associated with the mature epithelial cells of the luminal surface were more numerous than those associated with the immature cells of the crypts, where the R bodies predominated. A decreased number of C bodies was observed in ulcerative colitis. We concluded that the membrane-bound C bodies surrounding the microvilli were cellular in origin and arose from R bodies within the cytoplasm of the rectal epithelial cells.