Chromosome Marker Studies in the Graft-versus-Host Reaction in the Chick Embryo

Abstract

THE production of splenomegaly and other lesions by the injection of adult avian blood into the chick embryo is due to an immunological reaction between donor blood cells and host embryo tissues^1,2. Biggs and Payne³ have shown that the reaction is accompanied by proliferation of donor cells within the host spleen. They were able to distinguish donor (male) cells from host (female) cells by identifying the respective sex chromosome complements. Cells of male sex have a ZZ chromosome constitution, whereas female cells have a single Z chromosome^4,5. The Z chromosome is the only large mediocentric element in avian cells and is therefore readily identified in good chromosome preparations. Thus Biggs and Payne demonstrated proliferation of donor (ZZ) cells in the spleens of female embryos injected with cockerel blood. However, they found that the majority of dividing cells were of host type and they suggested that increased proliferation of host as well as donor elements must be responsible for splenic enlargement. Their investigation was limited to an analysis of 170 cells sampled from 9 embryo spleens removed 4 days after injection. Despite the obvious desirability of obtaining further information regarding the relative roles of donor and host proliferation in producing splenomegaly, no subsequent work has been reported. It would appear that technical difficulties involved in the preparation of clear metaphase figures from avian tissues have prevented further application of the method to the identification of cells.