CD5L, also known as CD5 antigen-like, is a soluble protein belonging to group B of the scavenger receptor cysteine-rich (SRCR) superfamily and contains three SRCR domains. It is a secreted glycoprotein and expressed by macrophages presentin lymphoid tissues (spleen, lymph node, thymus, and bone marrow). It binds to myelomonocytic and lymphoid cells and may play an important role in the regulation of the innate and adaptive immune systems. CD5L functions as a pattern recognition molecule by binding both lipoteichoic acid (LTA) on Gram positive and lipopolysaccharide (LPS) on Gram negative bacteria. and the SRCR domain 1 of CD5L retains both the LPS and LTA binding activities. In addtion, it is revealed that CD5L seems to play a role as an inhibitor of apoptosis.