The tumor necrosis factor alpha-stimulating region of galactose-inhibitable lectin of Entamoeba histolytica activates gamma interferon-primed macrophages for amebicidal activity mediated by nitric oxide

Infect Immun. 1997 Jul;65(7):2522-7. doi: 10.1128/iai.65.7.2522-2527.1997.


Entamoeba histolytica adheres via galactose-lectin (Gal-lectin) to human colonic mucins and intestinal epithelial cells as a prerequisite to amebic invasion. Native Gal-lectin is a protective antigen in the gerbil model of amebiasis. Amino acids 596 to 1082 of Gal-lectin mediate E. histolytica adherence to target cells and stimulate tumor necrosis factor alpha (TNF-alpha) production by naive murine bone marrow macrophages (BMM). Resistance to amebiasis requires an effective cell-mediated immune response against E. histolytica trophozoites mediated by nitric oxide (NO) released from activated macrophages. Herein, we determine whether the TNF-alpha-stimulating region of Gal-lectin can activate gamma interferon (IFN-gamma)-primed BMM for NO production and amebicidal activity. Native Gal-lectin (100 to 500 ng/ml) stimulated TNF-alpha and inducible nitric oxide synthase (iNOS) mRNA expression in IFN-gamma-primed BMM as did lipopolysaccharide (100 ng/ml). Primed BMM produced TNF-alpha and NO in response to Gal-lectin in a dose-dependent manner. Antilectin monoclonal antibody IG7, which recognizes a domain (amino acids 596 to 818) of the TNF-alpha mRNA-stimulating region of Gal-lectin, specifically inhibited TNF-alpha and iNOS mRNA induction and TNF-alpha and NO production by primed BMM in response to Gal-lectin (100 ng/ml). Simultaneous treatment of BMM with IFN-gamma and Gal-lectin (100 ng/ml) activated the cells to kill E. histolytica trophozoites, whereas IFN-gamma treatment alone had no effect. In the presence of monoclonal antibody 1G7 or aminoguanidine (an iNOS inhibitor), NO production and amebicidal activity were inhibited >80%. These results suggest that the TNF-alpha-stimulating region of native Gal-lectin is a potent stimulus of IFN-gamma-primed BMM for NO production, which is essential for host defense against amebiasis.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Antibodies, Monoclonal
  • Bone Marrow / immunology*
  • Entamoeba histolytica / immunology*
  • Entamoebiasis / immunology
  • Female
  • In Vitro Techniques
  • Interferon-gamma / pharmacology*
  • Lectins / pharmacology*
  • Macrophages / immunology*
  • Mice
  • Mice, Inbred BALB C
  • Nitric Oxide / biosynthesis
  • Nitric Oxide / physiology*
  • Nitric Oxide Synthase / metabolism
  • Protozoan Proteins / pharmacology*
  • RNA, Messenger / analysis
  • Tumor Necrosis Factor-alpha / biosynthesis*
  • Tumor Necrosis Factor-alpha / genetics


  • Antibodies, Monoclonal
  • Lectins
  • Protozoan Proteins
  • RNA, Messenger
  • Tumor Necrosis Factor-alpha
  • N-acetylgalactosamine inhibitable lectin 35-kDa subunit, Entamoeba histolytica
  • Nitric Oxide
  • Interferon-gamma
  • Nitric Oxide Synthase