The effects of foetuin on lymphocytes: lymphocyte-stimulating property

The effect of an isolated calf foetal protein, foetuin, on lymphocyte cultures in vitro was studied using bovine serum albumin and lyophilized calf serum as controls. Four different lots of foetuin were found to induce blast transformation and protein and DNA synthesis of human peripheral blood lymphocytes. The peak responses were reached after 5–6 days of culture. Lymphocytes from bovine mesenteric lymph-nodes were also stimulated after 6 days of culture. The lymphocyte stimulating property associated with foetuin was stable to freeze-thawing but destroyed by heating at 80°C for 60 min. HeLa cell growth promoting factor known to be present in ammonium sulphate-precipitated foetuin preparations was excluded as being responsible for the mitogenic effect observed.