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P LeMarbre, JJ Rinehart, NE Kay, R Vesella and HS Jacob
The mononuclear phagocyte is well established as an in vitro cytotoxic
effector cell for certain human tumors. The mechanism(s) for this action
remains unclear. Increased levels of lysozyme, a cationic enzyme
synthesized in large amounts by mononuclear phagocytes, are associated with
increased resistance to transplantable animal tumors. In this study, we
provide evidence that human lysozyme, isolated from the urine of leukemic
patients, has marked potentiating effects on human monocyte- tumor-cell
cytocidal activity. In addition, lysozyme-exposed monocytes incorporate
increased quantities of leucine, suggesting that monocytes are capable of
amplifying their own metabolic activation by secreting an endogenous
constituent. Tri-N-acetyl-glucosamine, a competitive inhibitor for the
active site of lysozyme, inhibits cytocidal activity. Conversely,
protamine, an extraneous albeit similarly positively charged molecule,
increases monocyte-mediated tumor cytotoxicity; this protamine effect is
negated by heparin. We conclude that lysozyme, at least partially by its
positive charge, is capable of enhancing in vitro monocyte tumor cell
cytotoxicity; its in vivo secretion may potentiate monocyte-tumor-cell
interaction.
This article has been cited by other articles:
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| Copyright © 1981 by American Society of Hematology Online ISSN: 1528-0020 | |||||||||
