[Toll-like receptor 4 expression and cytokine secretion in microglial cells induced by IgG stimulation].
OBJECTIVE
To investigate the effects of immunoglobulin G (IgG) on the expression of toll-like receptor 4 (TLR4) and secretion of cytokines in microglial cells in vitro.


METHODS
Cultured primary rat microglial cells were stimulated with different concentrations of rat IgG (2 mg/L, 20 mg/L, 200 mg/L) and lipopolysaccharide (LPS) 10 mg/L for 24 h, respectively. The TLR4 expression in the microglial cells was examined by immunofluorescence staining and tumor necrosis factor-alpha (TNF-alpha) and interferon-gamma (IFN-gamma) levels in the culture medium were assayed by ELISA.


RESULTS
IgG stimulation induced a significant TLR4 expression and TNF-alpha secretion in cultured microglial cells in a dose-dependent manner, while IFN-gamma was not detected in the same medium samples. As a positive control, LPS caused increases of TLR4 expression and both IFN-gamma and TNF-alpha production in the microglial cells.


CONCLUSIONS
TLR4 expression could be induced in microglia in vitro by non-pathogenic protein, IgG from the same species. Therefore, congeneric IgG stimulation might lead to proinflammmatory cytokine production, probably via MyD88-dependent pathway. This finding suggests that TLR4 may play more roles than pathogen recognition of innate immune reactivity, at least in the central nervous system.
Wu
Rui
R
College of Veterinary Medicine, Northwest A&F University, Yangling, China. wur2003@163.com
Liu
Ling
L
Peng
Zheng-wu
ZW
Duan
Xiao-li
XL
Wang
Bai-ren
BR
Jin
Ya-ping
YP
Kuang
Fang
F
D000818:Animals; D000831:Animals, Newborn; D002478:Cells, Cultured; D016207:Cytokines / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D004797:Enzyme-Linked Immunosorbent Assay; D005455:Fluorescent Antibody Technique; D007074:Immunoglobulin G / Q000494:pharmacology*; D007371:Interferon-gamma / Q000378:metabolism; D017628:Microglia / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D051197:Toll-Like Receptor 4 / Q000378:metabolism*; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
D016207:Cytokines; D007074:Immunoglobulin G; C495347:Tlr4 protein, rat; D051197:Toll-Like Receptor 4; D014409:Tumor Necrosis Factor-alpha; D007371:Interferon-gamma