CD5 Antigen Like Protein (CD5L)

Scavenger receptor cysteine-rich (SRCR) family members are among the proteins that regulate leukocyte function. One group of SRCR proteins includes CD5 and CD6, both of which have 3 SRCR-like domains each containing 8 cysteine residues in their extracellular region, a hydrophobic transmembrane domain, and a long cytoplasmic domain.

The predicted 347-amino acid protein, which they called Sp-alpha, has a 19-amino acid signal sequence followed by 3 cysteine-rich SRCR domains. Northern blot analysis detected 3 mRNAs of 2.4, 2.1, and 1.8 kb in spleen, lymph node, thymus, bone marrow, and fetal liver, but not in nonlymphoid tissues. Some resting myeloid cell lines, as well as peripheral blood monocytes, were capable of binding Sp-alpha.