 This gene is expressed primarily in the liver, and it is activated when monocytes differentiate into macrophages.Alternatively spliced transcript variants have been found for this gene, but the biological validity of some variants has not been determined.Apolipoprotein C1 has a length of 57 amino acids normally found in plasma and responsible for the activation of esterified lecithin cholesterol with an important role in the exchange of esterified cholesterol between lipoproteins and in removal of cholesterol from tissues.