CD5L, also known as CD5 antigen-like, plays a role in the regulation of the immune system. CD5L which is a secreted glycoprotein and expressed by macrophages presenting lymphoid tissues such as bone marrow, lymph node and thymus is up-regulated in macrophage at inflammatory sites. It sustains inflammatory reactions by both increasing the phagocytic capacity of macrophage and impeding the apoptosis of local macrophages, NK cells and T cells.