IL-10 release requires stronger toll-like receptor 4-triggering than TNF: a possible explanation for the selective effects of heterozygous TLR4 polymorphism Asp(299)Gly on IL-10 release.

The toll-like receptor 4 Asp(299)Gly polymorphism results in an inactive receptor. Heterozygosis is associated with reduced LPS-inducible IL-10 protein and IL-10 mRNA from blood leukocytes and isolated monocytes, while numerous other mediators are not affected. We could exclude that this effect is due to the differences in the kinetics of IL-10 release, in the expression of total surface TLR4 or in LPS-binding to monocytes between subjects heterozygous for the Asp(299)Gly polymorphism or homozygous carriers of the wild-type allele. Furthermore, we could show that IL-10 induction in general requires stronger LPS-triggering than TNF and is more sensitive to LPS inhibitors. The lower number of responsive wild-type TLR4 receptors on monocytes of heterozygotes may explain why only IL-10 release is affected.