Differential mRNA expression of Toll-like receptors and their adaptors in pleural effusions

Background and objective: Binding of Toll-like receptors (TLRs) to microbial or endogenous ligands activates and triggers the associated signalling pathway, which leads to the production of inflammatory cytokines and type I interferons. The extent of TLR pathway activation may vary with the ligands present in different pleural diseases. Methods: The relative mRNA expression levels of TLRs and their adaptors in pleural fluid were determined by PCR and gel electrophoresis in 36 transudative, 25 infectious and 39 malignant pleural effusions. Results: The relative mRNA expression levels of TLR8 and myeloid differentiation factor 88 were low in infectious effusions and that of ras-related C3 botulinum toxin substrate 1 was low in malignant pleural effusions. Different cellular components correlated significantly with the relative mRNA expression of TLRs or their adaptors in pleural effusions with different aetiologies. Conclusions: The relative mRNA expression profiles of TLRs and their adaptors in pleural fluid differ among transudative, infectious and malignant pleural effusions.