IL1B and rheumatoid arthritis: Historical ex vivo functional studies demonstrated that total macrophages isolated from active RA synovial tissue spontaneously released proinflammatory mediators (eg, TNF, IL-1β, IL-6,63 CXCL864 and CCL265) and are able to stimulate autologous T cells.66 Staining of these macrophages with the antibody recognising CD13, expressed on bone marrow-derived myeloid cells, alluded to the presence of at least two functionally distinct subpopulations that differed in their angiogenic properties.