Lectin-dependent neutrophil-mediated cytotoxicity against chicken erythrocytes: a model of non-myeloperoxidase-mediated oxygen-dependent killing by human neutrophils
Greene, W.H.; Colclough, L.; Anton, A.; Root, R.K.
Journal of Immunology 125(6): 2727-2734
1980
ISSN/ISBN: 0022-1767 PMID: 6253570 Document Number: 159571
To examine the role that O2 products of human neutrophils (PMN) might play in the killing of nucleated target cells, a model of lectin-mediated cytotoxicity was examined in detail. The plant lectin concanavalin A (Con A) was used to stimulate PMN to lyse 51Cr-labeled chicken red blood cells (CRBC) in a dose-dependent fashion. Evidence that PMN myeloperoxidase (MPO) was not involved in the lytic process was obtained by the failure of lysis to be inhibited by 1 mM sodium azide and the normal killing ability of totally MPO-deficient PMN. In keeping with the lack of involvement of MPO in this system, incubation of normal PMN with Con A and CRBC resulted in a minimal increment in MPO-mediated protein iodination. Con A-stimulated chronic granulomatous disease PMN were unable to lyse the target erythrocytes, which indicated that products of PMN oxidative metabolism must be required in this model. Addition of various O2 radical scavengers and H2O2 to suspensions of Con A-stimulated normal PMN and CRBC revealed the following: catalase and superoxide dismutase each inhibited lysis by 20-30%, whereas the combination of both enzymes inhibited lysis by 40-50%; lysis was not inhibited by the addition of mannitol, benzoate or histidine. This model of lectin-dependent PMN cytotoxicity is O2 dependent but MPO independent. The precise nature of the toxic O2 products remains to be identified, but the scavenger experiments suggest that both superoxide and H2O2 are involved and are additive in their effects. No clear evidence of a role for hydroxyl radical or singlet O2 could be obtained by adding scavengers of these radicals. This model may prove useful for the study of cytocidal events that involve O2 but exclude MPO as an essential reactant.