TLR6 and obstructive sleep apnea syndrome: In seven patients with severe OSA who had received more than 6 months of CPAP treatment, DNA methylation levels over CpG sites #1, #9 and #23 of the TLR2 promoter region, CpG sites #1 and #3 of the TLR6 gene body, and TLR2 and TLR6 protein expressions were all reduced, and DNA methylation levels over CpG sites #24 and #26 of the TLR2 promoter region were both elevated (Fig 5 and S12 Table).