SOME IMMUNOLOGIC ASPECTS OF LEUKEMIA

Investigations of Carrel and Elbeling¹ into the proliferative activity of blood leukocytes in tissue cultures have shown that homologous serum possesses a marked antiproliferative effect on polymorphonuclear leukocytes and lymphocytes. The first mentioned type of white blood cell disappears entirely from the culture in a few days, and the latter type in from one to two weeks. By a process of physiologic selectivity a pure culture of mononuclear cells remains, which can be kept alive for several months. Carrel and Ebeling concluded from this observation that homologous serum may possess a similar action in vivo, because the number of leukocytes would increase indefinitely if serum were not endowed with this property. They added that probably the increase of the growthinhibiting action of serum in the course of life determines a decrease in the activity of the white cells and modifies their secretions. They suggested, moreover, that possibly this is