The Identification of Cells During the Proliferative Phase of Spleen Enlargement of Chick Embryos Following Injection with Adult Blood

THE observation that grafting of chick embryos with adult spleen cells leads to enlargement of the embryonic spleen was first made by Murphy in 1916 but it was not until the demonstration of its immune nature (Simonsen, 1957) that this process was properly understood. Splenomegaly is nowadays regarded as a manifestation of the graft-versus-host reaction which occurs when embryos are challenged with immunologically competent cells, provided these differ from their host in at least one of the major histocompatibility antigens (Jaffe and McDermid, 1962). A number of puzzling features remain, one of which is the relative role played by donor and host components in the period of intense cellular proliferation. In the chicken, Murphy (1916) believed the enlargement to be due to the multiplication of embryo cells stimulated by the graft. Simonsen (1957) took the opposite view: namely that splenomegaly was the result of proliferating donor cells. An intermediate point …