Toll-like receptor (TLR) 4 polymorphisms are associated with a chronic course of sarcoidosis

Abstract

Summary The aetiology of sarcoidosis, an inflammatory granulomatous multi-system disorder, is unclear. It is thought to be the product of an unknown exogenous antigenic stimulus and an endogenous genetic susceptibility. Toll-like receptors (TLR) are signal molecules essential for the cellular response to bacterial cell wall components. Lipopolysaccharide (LPS), for example, binds to TLR 4. Two different polymorphisms for the TLR4 gene (Asp299Gly and Thr399Ile) have been described recently. This leads to a change in the extracellular matrix function of TLR4 and to impaired LPS signal transduction. We genotyped a total of 141 Caucasian patients with sarcoidosis and 141 healthy unrelated controls for the Asp299Gly and Thr399Ile polymorphisms in the TLR4 gene. The mutations were identified with polymerase chain reaction followed by restriction fragment length polymorphism (RFLP) analysis. Among sarcoidosis patients the prevalence for each Asp299Gly and Thr399Ile mutant allele was 15·6% (22/141). In the control group the prevalence was 5·67% (8/141) (P = 0·07). In the subgroup of patients with acute sarcoidosis there was no difference in the control group (P = 0·93), but there was a highly significant association between patients with a chronic course of sarcoidosis and TLR4 gene polymorphisms (P = 0·01).