Heterozygous toll-like receptor 4 polymorphism does not influence lipopolysaccharide-induced cytokine release in human whole blood

The heterozygous Asp299Gly mutation of the toll-like receptor (TLR) 4, the key receptor for lipopoiysaccharide (LPS), has been associated with attenuated inflammatory responses. When 160 healthy volunteers (9% heterozygous and 0.6% homozygous) were genotyped and their LPS-inducible cytokine release was assessed in an ex vivo whole blood test, the responses of heterozygotes did not differ significantly from those of wildtype carriers for any of the cytokines (tumor necrosis factor-α, interleukin [IL]-1β, IL-6, interferon-γ, and granulocyte colony-stimulating factor) or eicosanoids measured or for serum cytokines and C-reactive protein. Ten heterozygous subjects and 12 wild-type control subjects responded similarly to a graded series of LPS and Escherichia coli concentrations, excluding the possibility that allele-specific differences are evident only at low stimulus concentrations or in response to whole pathogens. These data demonstrate that the heterozygous Asp299Gly polymorphism does not exhibit a functional defect in cytokine release after the stimulation of blood monocytes.