Toll-like receptors 2 and 4 cell surface expression reflects endotoxin tolerance in Henoch-Schönlein purpura

We aimed to analyze the Toll-like receptor (TLR)2 and TLR4 expressions, which are known to be involved in the recognition of pathogens by the innate immune system, in patients with Henoch-Schönlein purpura. Twenty-three patients (10 males, 13 females, aged 4-16 years) with a clinical diagnosis of Henoch-Schönlein purpura were enrolled. Twenty healthy age-matched children (10 males, 10 females) served as controls. TLR2 and TLR4 expression levels on peripheral blood mononuclear cells (PBMCs) were determined by flow cytometric analysis. PBMCs were cultured with heat shock protein (HSP) 60 (1 microg/ml) as an endogenous ligand for TLR. Levels of TLR2 and TLR4 expression on PBMC were significantly lower in the Henoch- Schönlein purpura patients compared to healthy controls when stimulated with HSP60 and with lipopolysaccharide (LPS) (p < 0.05 for both). There was no significant difference between the stimulated and unstimulated samples from the patients. The lower TLR response to these ligands among these patients may reflect a tolerance to bacterial antigens. Further studies will clarify whether tolerance to microbial antigens may have a role in the pathogenesis and course of Henoch-Schönlein purpura.