Expression and function of sialoadhesin in rat alveolar macrophages.
Alveolar macrophages (Am&phi;) represent an immunologically distinct sub-population within the reticuloendothelial system. Phagocytosis and possibly antigen presentation by Am&phi; are essential components of specific and innate primary immune defence processes against inhaled material. The m&phi;-restricted sheep erythrocyte receptor sialoadhesin (Sn) is a member of the immunglobulin superfamily and binds specifically to sialic acid-containing structures such as selectins and was originally identified as the sheep erythrocyte receptor (SER) responsible for sialic acid-dependent binding of native sheep erythrocytes (SE) to resident murine bone marrow macrophages in rosetting assays. Sn expression has been demonstrated on murine and rat m&phi; in lymphatic organs and is recognised by the monoclonal antibody (mAb) ED3 in the rat. In addition, sialic acid-dependent receptor (SAR) activities that mediate rosette formation of alveolar, peritoneal, splenic and bone marrow-resident rat m&phi; with SE pretreated with gangliosides and SER-like activities between native SE and trypsinised Am&phi;, have been described. The binding activities of both SAR and Sn show similar characteristics suggesting that these molecules are closely structurally related or identical. To clarify the relationship between Sn, SAR and SER-like activities, the binding of mAb ED3 to isolated rat Am&phi; was investigated by flow cytometry and rosetting assays. It is demonstrated that rat Am&phi; express Sn and evidence is provided that SAR and SER-like activities are mediated by Sn.
Frei
K
K
Institute of Histology and Embryology, University of Vienna, Schwarzspanierstrasse 17, A-1090, Vienna, Austria. klemens.frei@akh-wien.ac.at
Steger
C
C
Samorapoompichit
P
P
Lucas
T
T
Förster
O
O
D000818:Animals; D002478:Cells, Cultured; D016676:Macrophages, Alveolar / Q000378:metabolism*; D008297:Male; D008562:Membrane Glycoproteins / Q000096:biosynthesis*; D019158:N-Acetylneuraminic Acid / Q000378:metabolism*; D051381:Rats; D011956:Receptors, Cell Surface / Q000378:metabolism; D011971:Receptors, Immunologic / Q000096:biosynthesis*; D012756:Sheep; D063267:Sialic Acid Binding Ig-like Lectin 1
D008562:Membrane Glycoproteins; D011956:Receptors, Cell Surface; D011971:Receptors, Immunologic; D063267:Sialic Acid Binding Ig-like Lectin 1; C092488:sialic acid receptor; D019158:N-Acetylneuraminic Acid