TLR1 and rheumatoid arthritis: This was not unexpected, as TLR2 has previously been reported to be expressed at a higher level on RA monocytes and stimulation with lipoteichoic acid (a TLR2 ligand that can activate both TLR1/2 and TLR2/6 heterodimers) could induce elevated levels of intracellular cytokines, as shown by flow cytometry [12].