The Complement System However,in the presence of an adaptive immune response,complement proteins interact with both its soluble and cellular components (antibodies,lymphocytes, activated macrophages,dendritic cells). Complement proteins circulate in plasma as inactive precursors.The Complement System However, in the presence of an adaptive immune response, complement proteins interact with both its soluble and cellular components (antibodies, lymphocytes, activated macrophages, dendritic cells). Complement proteins circulate in plasma as inactive precursors