HTR2B and rheumatoid arthritis: Monocytes in RA and OA showed different expression of many NTRs, including ADRB2, CHRNB1, VIPR1, HTR2B, NPY1R and HTR2A(Fig. 1f), however, except for ADRB2 and VIPR1(5.2% in RA and 11.5% in OA), the remaining NTRs were expressed on very few monocytes (Fig. 1d, f).