In seropositive RA biopsies, macrophage-enriched cell areas were on average significantly co-localized with higher presence of CD55+ lining as well as HLA-DRAHigh and CD34+ sublining fibroblast cells in the whole tissue volume (average Pearson’s R 0.76, p < 0.05, Supplementary Fig. 9a). Here, CD55 is linked to rheumatoid arthritis.