Ultracytochemical study of lytic complex insertion in the glycocalyx of red cells during immune hemolysis mediated by complement.

Ruthenium red (RR), a cationic dye and an ultrastructural tracer of cell membrane permeability, was used on sheep red blood cells after lysis produced by a specific antibody and guinea pig complement. In addition to the opacification of the glycocalyx, RR stained structures related to lytic complexes, which appeared as rod-like structures with variable dimensions (generally 45 nm in width, 75 nm in height) inserted in the glycocalyx of red cells. They extended across the external layer of the trilaminar plasma membrane without reaching the internal layer or the cytoplasm. RR staining visualized the internal configuration of the lytic complexes and revealed small channels measuring 10 nm in diameter localized within the complexes. These lytic complexes are thought to correspond to membrane attack complex of complement. To the best of our knowledge, this is the first report of ultrastructural positive staining of lytic complexes in thin sections, allowing visualization of their internal configuration and their insertion in the plasma membrane glycocalyx.