FRANK SET0 Zoology D e p a r t m e n t , U~z i v e r s i t y of O k l a k o m a , Nornznn, O k l a h o m c~ 73069
ABSTRACTKinetic studies with the splenomegaly assay and the in vivo antibody assay of marker allogeneic immunocompetent cells were made to ascertain when in embryonic development the capacity to actively reject foreign cells is manifested by the chick embryo. It was found that (1) the splenomegaly response elicited with equivalent amounts of immunologically competent cells was high in 14-day embryo hosts but much less in embryo hosts 16-, and 18day of age. Whereas the GVH reaction was effectively reduced in cyclophosphamide-pretreated 14-day hosts, no such effect was observed in older hosts;(2) the antibody production by allogeneic immunocytes, as measured with the in vivo assay, was high in 14-and 16-day embryo hosts, but significantly reduced in 18-day embryo and day-old chick hosts. In contrast the antibody output remained high in all cyclophosphamide-pretreated hosts; and (3) the marker immunocytes, cultured in embryo hosts for several days, maintained their antigen-responsive capacity unimpaired up to the seventeenth day of incubation but showed some loss by the eighteenth day. The experimental findings indicate that the host response during splenomegaly in young embryo hosts is not associated with graft rejection. However, coinciding with the reduction in splenomegaly in older hosts is rejection of donor cells. Alloimmune responsiveness exists as early as the development.
Despite the wide niention and use of genetic lethal factors, very little is known of their time and manner of action. Of the 557 or more lethals listed up to 1914 (Bridges and Brehme, '44) there were oiily 60 about which there was any information on the stage of death. The time of action of individual lethals has been studied by Sivertzev-Dobzalinsky ( '27) , Brehme ( '37, '39), and Rrody ( '40). Detailed studies on the manner of action of certain recessive lethals and chromosome deficiencies have been made by Hadorn ('37, '48, '5l), Li ( W), and Poulson ('37, '40, ,45).The first systematic study of the time of action of a large series of lethals was by Medvedev ('38, '39a, '39b), who reported oii 48 spontaneously occurring sex-linked recessive lethals. Oster ('52) studied the time of cessation of developinent of 55 sex-linked recessive lethals obtained from ultraviolet treated Drosophila melaNogaster. Rizki ( '52) studied the time of death of 72 autosomal lethals in D. zuiZZisto*ti obtained from three sources : spontaneously occurring, x-ray induced, and extracted from a wild population. This paper reports the results of studies beg-un in 1951 on a series of '77 second chromosoine lethals in D. melcmogaster.
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