Phenotype and pathological significance of MCAM(+) (CD146(+)) T cell subset in psoriatic arthritis

BACKGROUND: CD146 (MCAM-melanoma cell adhesion molecule) is a cell surface adhesion molecule for Laminin 411. T cells expressing MCAM are mainly responsible for IL-17 production. IL-17 secreting T helper cells (Th17 cells) are critical for the pathogenesis of psoriatic arthritis (PsA). Here we hypothesized enrichment of CD146(+)IL-17(+) memory T cells in PsA synovium and studied the association of CD146 expression and CD4(+)IL-17(+) activated memory (CD11a(+)CD45RO(+)) T cells in synovial fluid and blood of PSA, rheumatoid arthritis (RA, a positive control) and osteoarthritis (OA) patients. METHODS: Hi-D FACS studies were done to identify IL-17 in CD4(+)CD146(+)CD45RO(+) and CD8(+)CD146(+)CD45RO(+) T cells. RESULTS: We observed that effector CD146(+)(MCAM(+)) T cells are enriched at the synovial inflammation site in PsA. CONCLUSION: As CD146(+) T cells are a key resource for IL-17 it is likely that the enrichment of these MCAM(+) pathologic cells are critical for the disease process of PsA.