title: LDL acts as an opsonin enhancing the phagocytosis of group A Streptococcus by monocyte and whole human blood.
abstract: Low-density lipoprotein (LDL) binds to group A Streptococcus (GAS) through Sc11 protein, and scavenger receptor CD36 of monocyte mediates the endocytosis of native or modified LDL. Therefore, we hypothesized that LDL might be an opsonin enhancing the phagocytosis of LDL-bound GAS by monocyte. The results showed that LDL could significantly promote U937 cell to phagocytose M28 (ATCC BAA1064) and M41 (ATCC 12373, AM41)-type GAS, and the phagocytosis rates were significantly increased, compared with LDL-free group. LDL, however, did not enhance the phagocytosis of M41 (CMCC 32198, CM41) or M6 (ATCC BAA946)-type GAS since these two strains did not bind to LDL. CD36 was the major scavenger receptor mediating the uptake of LDL-bound GAS by monocyte U937 cells since anti-CD36 antibody abolished the phagocytosis of LDL-opsonized GAS but anti-CD4 antibody did not. Most of AM41-type GAS cells were killed in human blood, whereas only a few CM41-type cells were phagocytosed. Moreover, recombinant Scl1 (rScl1) derived from M41-type GAS could significantly decrease the opsonophagocytosis of AM41 but not CM41-type GAS because the rScl1 competitively blocked the binding of AM41-type GAS to LDL. Therefore, our findings suggest that LDL may be an opsonin to enhance CD36-dependent opsonic phagocytosis of GAS by monocyte.
authors.affiliation: Research Center of Plasma Lipoprotein Immunology, Inner Mongolia Agricultural University, Huhhot, China.|Key Laboratory of Animal Clinic Diagnosis and Treatment, Ministry of Agriculture of China, Inner Mongolia Agricultural University, Huhhot, China.
authors.forename: Lulei
authors.initials: L
authors.lastname: Zhou
authors.affiliation: Research Center of Plasma Lipoprotein Immunology, Inner Mongolia Agricultural University, Huhhot, China.|Key Laboratory of Animal Clinic Diagnosis and Treatment, Ministry of Agriculture of China, Inner Mongolia Agricultural University, Huhhot, China.
authors.forename: Ling
authors.initials: L
authors.lastname: Liu
authors.affiliation: Research Center of Plasma Lipoprotein Immunology, Inner Mongolia Agricultural University, Huhhot, China.|Key Laboratory of Animal Clinic Diagnosis and Treatment, Ministry of Agriculture of China, Inner Mongolia Agricultural University, Huhhot, China.
authors.forename: Jinli
authors.initials: J
authors.lastname: Yang
authors.affiliation: Research Center of Plasma Lipoprotein Immunology, Inner Mongolia Agricultural University, Huhhot, China.|Key Laboratory of Animal Clinic Diagnosis and Treatment, Ministry of Agriculture of China, Inner Mongolia Agricultural University, Huhhot, China.
authors.forename: Yuxin
authors.initials: Y
authors.lastname: Li
authors.affiliation: Research Center of Plasma Lipoprotein Immunology, Inner Mongolia Agricultural University, Huhhot, China.|Key Laboratory of Animal Clinic Diagnosis and Treatment, Ministry of Agriculture of China, Inner Mongolia Agricultural University, Huhhot, China.
authors.forename: Wencheng
authors.initials: W
authors.lastname: Bai
authors.affiliation: Research Center of Plasma Lipoprotein Immunology, Inner Mongolia Agricultural University, Huhhot, China.|Key Laboratory of Animal Clinic Diagnosis and Treatment, Ministry of Agriculture of China, Inner Mongolia Agricultural University, Huhhot, China.
authors.forename: Na
authors.initials: N
authors.lastname: Liu
authors.affiliation: Research Center of Plasma Lipoprotein Immunology, Inner Mongolia Agricultural University, Huhhot, China.|Key Laboratory of Animal Clinic Diagnosis and Treatment, Ministry of Agriculture of China, Inner Mongolia Agricultural University, Huhhot, China.
authors.forename: Wenlong
authors.initials: W
authors.lastname: Li
authors.affiliation: Research Center of Plasma Lipoprotein Immunology, Inner Mongolia Agricultural University, Huhhot, China.|College of Public Health, Inner Mongolia Medical University, Huhhot, China.
authors.forename: Yumin
authors.initials: Y
authors.lastname: Gao
authors.affiliation: Research Center of Plasma Lipoprotein Immunology, Inner Mongolia Agricultural University, Huhhot, China.|College of Basic Medicine, Inner Mongolia Medical University, Huhhot, China.
authors.forename: Liping
authors.initials: L
authors.lastname: Xu
authors.affiliation: Research Center of Plasma Lipoprotein Immunology, Inner Mongolia Agricultural University, Huhhot, China.|Key Laboratory of Animal Clinic Diagnosis and Treatment, Ministry of Agriculture of China, Inner Mongolia Agricultural University, Huhhot, China.
authors.forename: Zhi
authors.initials: Z
authors.lastname: Liu
authors.affiliation: Research Center of Plasma Lipoprotein Immunology, Inner Mongolia Agricultural University, Huhhot, China. han-runlin@163.com.|Key Laboratory of Animal Clinic Diagnosis and Treatment, Ministry of Agriculture of China, Inner Mongolia Agricultural University, Huhhot, China. han-runlin@163.com.
authors.forename: Runlin
authors.initials: R
authors.lastname: Han
mesh_terms: D000911:Antibodies, Monoclonal / Q000494:pharmacology; D001426:Bacterial Proteins / Q000494:pharmacology; D018955:CD36 Antigens / Q000037:antagonists & inhibitors; D002460:Cell Line; D002478:Cells, Cultured; D003094:Collagen / Q000494:pharmacology; D006801:Humans; D008077:Lipoproteins, LDL / Q000378:metabolism*; D009000:Monocytes / Q000187:drug effects / Q000276:immunology* / Q000378:metabolism*; D009895:Opsonin Proteins / Q000378:metabolism*; D010587:Phagocytosis / Q000187:drug effects / Q000276:immunology*; D011994:Recombinant Proteins / Q000494:pharmacology; D013290:Streptococcal Infections / Q000276:immunology / Q000378:metabolism / Q000382:microbiology; D013297:Streptococcus pyogenes / Q000276:immunology*; D020298:U937 Cells
chemical_list: D000911:Antibodies, Monoclonal; D001426:Bacterial Proteins; D018955:CD36 Antigens; D008077:Lipoproteins, LDL; D009895:Opsonin Proteins; D011994:Recombinant Proteins; C423454:Scl1 protein, Streptococcus; D003094:Collagen
keywords: Group A Streptococcus; Low-density lipoprotein; Monocyte; Opsonin; Phagocytosis