<unk>  is expressed by activated T cells of both the CD4+ and CD8+ lineages. Although it is thought to function mainly in co-stimulating those cell types to support their activation by antigen presenting cells expressing its ligand<unk> L),<unk>  is also expressed on dendritic cells, B cells, NK cells, neutrophils and macrophages.
CD137
CD23
CD74
CD80
CCR5
CCR2
CD86
IL-2 receptor