The formation of ultrastructural membrane lesions of varying size during cell mediated cytolysis effected by human peripheral blood leukocytes was recently reported by Dourmashkin et al. and Henkart et al. Using cloned mouse natural killer (NK) cells as effectors and YAC-1 cells or rabbit erythrocytes as targets, the authors report two types of membrane lesions with inner diameters of 16 ± 2 nm and ~5 nm, respectively. These lesions arise by membrane insertion of tubular complexes that may be assembled from subunits during the cytolytic reaction. The tubules are detected on target membranes by immune electron microscopy and appear to form transmembrane channels as seen in ultrathin sections. Both tubules are partially purified by membrane extraction with SDS and gel filtration in deoxycholate containing buffer. Based on the correlation of tubule assembly and cytolysis and on their detection on target membranes, it is suggested that both types of tubules may be related to cytolysis.
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