CD5L is a soluble glycoprotein that contains three SRCR domains . These domains are crucial for its function and are encoded by a single exon . The protein is expressed in various lymphoid tissues, including the spleen, lymph nodes, thymus, and bone marrow . It binds to myelomonocytic and lymphoid cells, playing a significant role in the regulation of both the innate and adaptive immune systems .
Initially identified as an apoptosis inhibitor, CD5L has been found to have several other functions . It acts as a pattern recognition molecule by binding to lipoteichoic acid (LTA) on Gram-positive bacteria and lipopolysaccharide (LPS) on Gram-negative bacteria . This binding activity is retained in the SRCR domain 1 of CD5L .
In addition to its role in immune response, CD5L is involved in various diseases. For instance, it has been implicated in the pathogenesis of chronic obstructive pulmonary disease (COPD). Studies have shown that CD5L facilitates the development of COPD by upregulating matrix metalloprotease (MMP)-12 . Higher levels of CD5L in the blood are associated with increased disease severity and poor prognosis in COPD patients .
Recombinant CD5L proteins are often used in research to study its functions and interactions. These proteins are typically expressed in host cells such as HEK293 cells and are purified to high levels of purity . The recombinant proteins are usually provided as lyophilized powder and can be reconstituted for experimental use .