Identification of the major lectin-binding surface proteins of human neutrophils and alveolar macrophages

Concanavalin A (Con A) and wheat germ agglutinin (WGA) are frequently used as stimuli of neutrophils and macrophages. While the effects of these lectins on cell function are presumably mediated by interaction with cell-surface molecules, the target structures on the cell surface involved are not well defined. We have used the techniques of lactoperoxidase catalyzed cell-surface iodination, lectin affinity chromatography, monoclonal antibody immunoprecipitation, and NaDodSO4- polyacrylamide gel electrophoresis to study the surface proteins of human neutrophils and alveolar macrophages that react with six lectins including Con A and WGA. We found that several major surface-labeled proteins of neutrophils bound Con A. Four of these proteins were identified by immunoprecipitation as members of the LFA-1/HMac- 1/gp150,95 adhesion glycoprotein family. Con A also bound CR1 and a 135- kd surface-labeled protein recognized by CD15 monoclonal antibodies. WGA also bound many of these proteins, but had a much lower avidity for CR1. All three of the major surface-labeled proteins of human alveolar macrophages bound to Con A, including the 183-kd mannose receptor and the 30-kd smoking-associated protein. WGA also bound the 183-kd macrophage protein, but not the 30-kd protein. These results should aid the understanding of studies using these lectins as stimuli.