Secretion of interleukin-17 by CD8Â + T cells expressing CD146 (MCAM)

•CD8+ T cells expressing CD146 secrete IL-17 and have a Tc17 genotype and phenotype.•CD146+ Tc17 cells are present in low levels in healthy adults.•Levels of CD146+ Tc17 cells are elevated in Behcet's disease and birdshot uveitis.

Interleukin-17 (IL-17) has been associated with the pathogenesis of numerous autoimmune diseases. CD4 + T cells secreting IL-17 are termed Th17 cells. CD8 + T cells, designated Tc17 cells, are also capable of secreting IL-17. Here we describe a population of Tc17 cells characterized by the expression of surface CD146, an endothelial adhesion molecule. These cells display signatures of a human Tc17 genotype and phenotype. Circulating  CD8+CD146 + T cells are present in low levels in healthy adults. Elevations in CD8 +CD146 + T cells are found in Behcet's disease and birdshot retinochoroidopathy, which have been reported to have HLA class I associations. Sarcoidosis does not have a class I association and displays an increase in CD4 + CD146 + T cells but not in  CD8+CD146 + T cells. CD146 on these cells may facilitate their ability to bind to, and migrate through, endothelium, as has been reported for CD4 +CD146 + T cells.