The killing of Leishmania major by human macrophages is mediated by nitric oxide induced after ligation of the Fc epsilon RII/CD23 surface antigen.

Abstract

Serum IgE concentrations and the expression of the low-affinity receptor for IgE (FceRHl/CD23) Nitric oxide (NO) generated by activated murine macrophages is cytostatic or cytotoxic for a variety of pathogens, including Leishmania major, Plasmodium falciparum, Schistosoma mansoni, Trypanosoma cruzi, and Toxoplasma gondii (1-6). NO is generated from the oxidation of the terminal guanido nitrogen atom(s) of L-arginine by an NADPH-dependent enzyme, the NO synthase (NOS) (7-9). In murine macrophages, NOS activity is induced by lipopolysaccharide (LPS) (9) IgE-IC) or by a specific monoclonal antibody (mAb) to CD23 (CD23 mAb) promotes the generation of cGMP. Simultaneous measurement of the generation of nitrite (NO-j) indicated that the enhanced production of cGMP is consequent to activation of the L-arginine:NO pathway.The low-affinity receptor for IgE (FceRII/CD23) is also expressed on normal human monocytes/macrophages after their activation in vivo (22,23). Studies in patients infected with Leishmania braziliensis or in disease-free, immunoreactive donors have shown both in situ CD23 expression and serum IgE concentrations to be increased in these conditions (23). We have, therefore, studied whether cell activation through ligation of the membrane receptor CD23 induces the L-arginine:NO pathway and results in leishmanicidal activity in human macrophages. MATERIALS AND METHODSReagents. The following reagents were used: recombinant human interleukin 4 (IL-4; a gift from J. Banchereau, Schering-Plough); IFN--y (a gift from J. M. Mencia-Huerta, Institut Beaufour, Paris); TNF-a and anti-TNF-a mAb (Genzyme); human IgE (Stallergene, Paris), and goat anti-human IgE (Nordic, Tilburg, The Netherlands). Polymyxin B, LPS (Escherichia coli 055, L-2880), NG-monomethyl-L-arginine (L-NMMA), D-NMMA, L-arginine, D-arginine, superoxide dismutase (SOD), and catalase were all obtained from Sigma.Cells. Human mononuclear cells were obtained by Ficoll gradient separation of peripheral blood leukocytes from healthy volunteers. Monocytes were separated from lymphocytes by adherence to plastic dishes coated with fetal calf serum as described (24). After this procedure, >90% of cells expressed CD14 antigen and displayed cytochemical characteristics of monocytes (24). The cells were then incubated in Dulbecco's modified Eagle's medium (DMEM) supplemented with nonessential L-amino acids, sodium pyruvate, glutamine, penicillin, streptomycin, and 10% (vol/vol) fetal calf serum (all from GIBCO). The culture medium was routinely controlled for the absence of a direct activation effect on human monocytes (CD23 expression and TNF-a production as activation Abbreviations: mAb, monoclonal antibody; CD23 mAb, anti-CD23 mAb; IgE-IC, IgE-anti-IgE immune complexes; L-NMMA, NA3-monomethyl-L-arginine; LPS, lipopolysaccharide; NOS, NO synthase; iNOS, inducible NOS; IFN-y, interferon y; IL, interleukin; TNF-a, tumor necrosis factor ai; SOD, superoxide dismutase; HPRT, hypoxanthine phosphoribosyltransferase. tTo whom reprint requests should be ad...

Bacterial infection induces nitric oxide synthase in human neutrophils.

“…Recently, neutrophils within human buffy coat preparations stimulated with a mixture of interleukin-1, tumor necrosis factor ␣, and interferon-␥ were shown to contain iNOS mRNA and protein, however iNOS was detected in only 20% of the stimulated neutrophils (41). Studies with monocytes/macrophages indicate that these cells can produce NO after infection with mycobacteria (17) or human immunodeficiency virus type I (42) and also after cross-linking of the surface receptor CD69 (43) or ligation of Fc⑀II/CD23 (44,45). Because NO is increased under conditions where the inducing agents are undefined, the combination of microbial products and cytokines, that induces iNOS in human disease states, warrants further investigation.…”

Interferon gamma and interleukin 4 stimulate prolonged expression of inducible nitric oxide synthase in human airway epithelium through synthesis of soluble mediators.

“…However, iNOS gene expression in HAEC was not related to NO production, as presence of NOS inhibitor did not affect iNOS gene expression. Similarly, previous reports have suggested that IL-4 and IFN␥ induce activation of iNOS gene expression through ligation of the low-affinity IgE receptor CD23 in human monocytes, keratinocytes, and eosinophils (45). CD23 may be induced by IL-4 and be cell associated or in a soluble form cleaved into the supernatant (46).…”

Human monocytic U937 cells transfected with human hepatic inducible nitric oxide synthase exhibit leishmanicidal activity

“…However, the precise conditions allowing reproducible NO synthesis by human M in culture remain to be defined. In this respect, the study by Vouldoukis and collaborators [30] demonstrating human M iNOS activation and leishmanicidal activity through CD23 cross-linking (CD23 mAb or IgE) is of particular interest. Our results clearly demonstrate that, once iNOS expression is induced and provided that a source of BH 4 is available, human M possess the required machinery to exert NO-dependent microbicidal activity.…”