One report on RA patients proposed a protective role for CD169+ macrophages, while others noted a positive correlation of circulating CD169+ myeloid cells with worse and extra-glandular disease in SS and dermatomyositis.356–358 Given the recent reports on potentially pathogenic CD8 T cells, and reductions in synovial CD8 T cells being associated with clinical responses to rituximab in RA patients, we favor the hypothesis that CD169+ macrophages are pathogenic in IMID.161,171,359–363. Here, SIGLEC1 is linked to synovial sarcoma.