Mammalian chimaeras / Anne McLaren.

  • McLaren, Anne.
Date:
[1976]
Catalogue details

Licence: Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0)

Credit: Mammalian chimaeras / Anne McLaren. Source: Wellcome Collection.

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    2 What is a chimaera ? Fig. 1. Etruscan chimaera, made of bronze, combining structures of lion, serpent and goat. From Cambridge Ancient History, Vol. 1 of Plates, pp. 336-7. London, Cambridge University Press. Reproduced by kind permission of the Mansell Collection. and embryo, or from one embryo to another. For example, a pair of twins studied by Booth et al. (1957) both had a mixture of red cells in their blood; Mr Wa. had 86 % group A and 14 % group О cells, while his twin sister Miss Wa. had 99 % О and 1 % A cells. The two cell populations proved to differ also at the Rhesus, Duffy, Kidd and Dombrock loci. Such individuals raise critical immunological problems. An analogous situation can be pro¬ duced experimentally by giving an animal a lethal dose of radiation to knock out its own immune system, and then 'rescuing' it by a bone marrow trans¬ plant from agenetically different individual. The study of'radiation chimaeras' has contributed greatly to transplantation biology (Micklem & Loutit, 1966). In cattle, twin embryos almost always share a common placental circula¬ tion, and secondary chimaerism can readily be detected in the blood. Unlike the situation of Mr Wa. and his sister, if one component predominates in the blood of one member of a cattle twin pair, the same component tends to be in the majority in the other twin also, at least in the adult (Marcum, 1974). When the twins are of opposite sexes, the female nearly always develops as a sterile freemartin (a phenomenon known already in Roman times), and the male co-twin is also affected. The impact of secondary chimaerism on sexual development is discussed briefly in Chapter 4. Sheep, goat and pig twins only