In consistence with the fact that macrophages and lymphocytes express CB2[20, 21], immunofluorescence double staining of the RA synovial tissues revealed CB2 expression on the synovial CD68+ macrophages, CD4+ T cells, CD8+ T cells, CD21+ B cells and vimentin+ fibroblast-like appearance cells (Figure 1F). Here, CD4 is linked to rheumatoid arthritis.