Age-associated alterations in toll-like receptor (TLR) expression in human monocytes. (A) Data shown are percent-positive monocytes for TLR1 (older n = 119, young n = 78), TLR2 (older n = 116, young n = 78), TLR4 (older n = 118, young n = 79), TLR5 (older n = 38, young n = 47), and TLR6 (older n = 90, young n = 69) surface expression. Values indicate the means ± SEM in young and older adults; asterisks indicate statistical significance between young and older cohort (**P < 0.01). (B) Densitometry of immunoblot of TLR5 in monocytes from 21 pairs of younger and older subjects. Densitometry shows the means ± SEM of the ratio of TLR5 to β-actin. Asterisks indicate statistical significance between younger and older cohort (**P < 0.01). (C) The data display mRNA expression levels of the indicated TLRs in purified monocytes from young (n = 23) and older adults (n = 26). mRNA levels were quantified by qPCR and normalized to β-actin. Data shown are the median with interquartile range; asterisks indicate statistical significance between young and older cohort (*P < 0.05 and ***P < 0.001).