The ultrastructure of the tubular complex in the cytoplasm of cytolytic T lymphocytes

Different pathways of the release of cytotoxic proteins in LAK cells

Human LAK cells were shown to release cytotoxic proteins by both Ca(2+)-dependent and Ca(2+)-independent mechanisms. CD3+ CD8+ CD16- and CD16+ CD8+ CD3- LAK cells were co-incubated with target cells in the presence of 4 mM EGTA. Although EGTA inhibited the exocytosis of cytolytic granules, supernatants obtained were cytotoxic for target cells. Cytotoxicity of CD3+ LAK cells and CD16+ LAK cells was due to cytotoxic proteins with MW 75 (p75), 35 (p35) and 22 (p22) kDa. LAK cells were also shown to release cytotoxic proteins by way of continuous secretion. After co-incubation in the absence of target cells LAK cells can secrete cytotoxic proteins with MW 75 (p75), 55 (p55), 38 (p38), 35 (p35), 25 (p25), 22 (p22) and 17 (p17) kDa.

Large granular lymphocytes: morphological studies

Large granular lymphocytes from normal human blood were enriched by centrifugation on discontinuous Percoll density gradients. Their capacity for natural killing, but not for phagocytosis of yeast cells, was demonstrated. Large granular lymphocytes are characterized in electron microscopy by their fine structure, especially by typical granules and by inclusions of tubular structures in a parallel array. Their lymphocyte nature is supported by activity of acid-alpha-naphthyl acetate esterase and by the absence of myelo-peroxidase (POX) and of macrophage POX. The Fc gamma receptor of their cell membrane is marked by soluble POX-anti-POX-complexes; labeled parts of their membrane are not incorporated into the cytoplasm as in monocytes.