Flow cytometry analysis of HLA-B27 and HLA-B7 transduced cells. Flow cytometry analysis of HLA-B27 and HLA-B7 transduced cells. (A) ATDC5 cells. (B) hPDCs were stained with an HLA-B27 antibody and subsequently with a PE-linked secondary antibody. There is a very strong cross-reactivity known between HLA-B7-positive cells and the HLA-B27 antibody, as the antibody used binds to both HLA-B27 and HLA-B7. Cells were first gated on forward scatter and side scatter; subsequently, HLA-B27/B7 positivity was determined by looking at PE signal versus side scatter (ATDC5) or forward scatter (hPDC). The percentage of HLA-B27-positive and HLA-B27-negative cells is noted above the plots. (C) Expression of HLA-B27 measured by quantitative RT-PCR, with an HLA-B27-specific primer, at the different time point during differentiation of ATDC5 cells, hPDCs during chondrogenesis and hPDCs during osteogenesis. FSC, forward-scattered; SSC, side-scattered. Barbara Neerinckx et al. RMD Open 2017;3:e000451 Copyright © BMJ Publishing Group & EULAR. All rights reserved.