Polish Journal of Microbiology 2006, Vol. 55, No 2, 95 101 Natural Mannose-Binding Lectin (MBL) Down-regulates Phagocytosis of Helicobacter pylori DOMINIK STRAPAGIEL 1 , ANETA GRÊBOWSKA 1 , BARBARA RÓ¯ALSKA 1 , LEOKADIA B¥K-ROMANISZYN 2 , EL¯BIETA CZKWIANIANC 2 , IZABELA P£ANETA-MA£ECKA 2 , TOMASZ RECHCIÑSKI 3 , WIES£AWA RUDNICKA 1 and MAGDALENA CHMIELA 1 1 Department of Immunology and Infectious Biology, University of £ód, 90-237 £ód, Banacha 12/16, Poland, 2 Institute Mother Health Center, 93-338 £ód, Rzgowska 281 Poland, 3 Medical University in £ód, 91-347 £ód, Kniaziewicza 1/5, Poland Received 20 December 2005, revised 10 February 2006, accepted 13 February 2006 Abstract Considering the role of lectin-carbohydrate interactions between Helicobacter pylori bacteria and the host cells we addressed the question on how mannose binding lectin  MBL, present in human plasma, may influence the phagocytosis of H. pylori by peripheral blood granulocytes. For phagocytosis assay the granulocytes separated from peripheral blood of healthy H. pylori-seronegative donors were used. Phagocytosis was estimated by fluorescence assay using FITC-labelled H. pylori cells. The MBL level in the serum samples as well as MBL-binding to H. pylori bacteria were estimated by ELISA. In this study all H. pylori isolates bound recombinant mannose binding lectin-MBL as shown by ELISA. The ingestion of H. pylori bacteria in the medium with human serum depleted in natural MBL (nMBL) was more intensive than in the medium with complete serum containing nMBL. Moreover, the ingestion of H. pylori bacteria in the medium with complete serum was increased by an addition of anti-rMBL IgG. The results indicate that interaction of bacterial and host lectins may regulate the phagocytosis of H. pylori bacteria and in this way influence an outcome of the infection caused by these microbes. Key words: Helicobacter pylori, mannose binding lectin (MBL), phagocytosis Introduction Helicobacter pylori related gastroduodenal infections are associated with strong infiltration of the gas- tric mucosa by neutrophils, macrophages, lymphocytes and plasma cells (Rudnicka and Andersen, 1999). Despite mobilization of phagocytes to inflammatory foci, the bacteria are not eliminated. It has been suggested that they may evade destruction by phagocytes due to a temporary persistence in the cytosol of epithelial cells (Petersen and Krogfeld, 2003). Many H. pylori strains express adhesin proteins that bind to specific host cell macromolecule receptors. The best defined H. pylori adhesin-receptor interaction, described by Ilver et al. (1998), is that between the Lewis b (Le b) blood group antigen binding adhesin, BabA, a member of a family of H. pylori outer membrane proteins. Mahdavi et al. (2002), identified sialyl-dimeric Lewis X glycosphingolipid as a receptor for H. pylori. The corresponding sialic-acid-binding adhesin (SabA) was isolated and the sabA gene was identified (Mahdavi et al., 2002). It has also been established that H. pylori strains express heparan sulphate binding proteins (Hirmo et al., 1995). Two molecular mechanisms of microbial recognition by phagocytes are distinguished: direct  opsonin independent, and indirect  opsonin dependent (Ofek et al., 1995) In our previous study we found that antibodies specific to various H. pylori antigens may have opposite effects on the course of phagocytosis of these bacteria. We showed that opsonization of H. pylori with anti-Lewis X monoclonal antibody (IgM) 1 Corresponding author: Magdalena Chmiela, Department of Immunology and Infectious Biology, University of £ód, Poland, Banacha 12/16, 90-237 £ód, Poland. Fax: (48) 42, 6655818; E-mail: chmiela@biol.uni.lodz.pl; Tel: (48) 42, 6354472