Incorporation of Bacterial Lipopolysaccharide by Human Leu-11a (+) Natural Killer Cells: Ultrastructural and Functional Correlations

摘要

In the present report, we have studied the incorporation of LP S by Leu-11a(+) cells and sought to correlate the resulting ultrastructural changes with altered function. Lipopolysaccharides (LPS) of gram-negative bacteria are to augment the ability of macrophages and natural killer (NK) cells to lyse susceptible target cells. In the present studies, we sought correlations between the ultrastructural changes and function of Leu-11(a+) cells from the peripheral blood mononuclear cells which occurred as a result of their incorporation of LPS. We also studied the effect of LPS on the NK activity of purified Leu-11(a+) cells. LPS samples from E. coli and Pseudomonas aeruginosa were utilized. A double-immunolabeling technique employing immunogold and immunoperoxidase markers was used to identify the Leu-11a(+) cells with incorporated LPS. Pinocytosis, phagocytosis, and direct insertion into membrane bilayers appeared to be the routes for incorporation of LPS by Leu-11a(+) cells. Subsequent ultrastructural effects included dilation of intracellular membrane compartments, formation of tubuloreticular inclusions and increased acid phosphatase activity. Result suggests that LPS may have direct effect on the NK cell activity. Tests of peripheral blood mononuclear cell samples after LPS treatment showed up to a 2-fold increase in NK cytotoxicity and a dose-related increase of in vitro interferon production. This suggests that, in addition to any direct effect of LPS, cytotoxic activity could be indirectly augmented as a result of autocrine or paracrine interferon, or lymphokine production. Keywords: Immunoelectron microscopy; Cytotoxicity; Phagocytosis; Reprints. (kt)