Anti-lipopolysaccharide egg yolk antibodies enhance the phagocytosis of mammalian phagocytes

Macrophages play crucial roles in combatting infectious diseases by promoting inflammation and phagocytosis. The decline of macrophage phagocytic function will bring many serious consequences, including weakened pathogen clearance. As an avian antibody, immunoglobulin Y (IgY) has been widely used in preventing and treating infectious diseases, but whether it can enhance the phagocytic ability of mammalian macrophages in order to clear pathogens is still unknown. In this study, mouse peritoneal macrophages and THP-1 cells were cultured with anti-lipopolysaccharide (LPS) IgY in vivo or in vitro, respectively. Morphological observation, ELISA, fluorescence immunoassays and flow cytometry were used to study whether IgY could enhance phagocytosis of mammalian macrophages. It was found that without anti-LPS IgY, mouse peritoneal macrophages showed adherent growth with no differentiation and little pseudopod extension; but with anti-LPS IgY, peritoneal macrophages presented more significant characteristics in adherent growth, extension deformation and protruding pseudopods. With flow cytometry, the macrophages from mice injected with anti-LPS IgY exhibited a significantly higher percentage of phagocytosis and index (90.83±2.59% and 4.45±0.13 respectively) compared with phosphate buffered saline (PBS) groups (64.32±1.5%, and 2.36±0.11) and non-immunized groups (65.94%±1.4%, and 2.4±0.15). With phorbol-12-myristate-13-acetate (PMA)-induced THP-1 cells, similar results were found; the percentage and index were significantly higher, with larger body and more pseudopods, for THP-1 cells that were co-incubated with anti-LPS IgY (79.83±0.38% and 2.64±0.03), compared with cells that were co-incubated with PBS (68.07±0.52%, and 1.88±0.03) or non-immunized IgY (74.89±1.14% and 2.30±0.02). The results showed that anti-LPS IgY was effective in promoting the growth of macrophages, pseudopod extension and stronger phagocytic capacity. Our study indicated that anti-LPS IgY could enhance the phagocytic capacity of mammalian macrophages to internalize pathogens more effectively with larger body and more pseudopods. This may be important to encourage IgY to be used to prevent and treat infectious diseases.