The First Appearance of Specific Antigens during the Induction of the Lens1

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Abstract
Presumptive lens ectoderm with associated eye-cup from 5 – 17-somite chick embryos was explanted in ‘normal’ medium, ‘anti-myosin’ medium, and a medium containing lens antibodies. The control explants in ‘normal’ and ‘anti-myosin’ medium showed lens formation in 80-100 per cent, of the cases (Text-fig. 1); the explants in ‘anti-lens’ medium showed degeneration and necrosis of the future lens area, indicating the presence of substances (lens antigens) capable of reacting with lens antibodies (Text-fig. 1). Explants from embryos with 18 or more somites in ‘anti-lens’ medium formed lenses as the controls. Presumptive lens ectoderm without the associated eye-cup from 7 – 20-somite embryos was cultured on a ‘normal’ and ‘anti-lens’ medium. The controls showed epithelial membranous outgrowth in 80 –100 per cent, of the explants (Text-fig. 3; Table 1). Explants on ‘anti-lens’ medium showed outgrowth similar to controls when obtained from embryos younger than 11 and older than 17 somites, but showed degeneration when obtained from 11-to 17-somite embryos, indicating the formation of the first reacting substances (lens antigens) at the 11-somite stage (Text-fig. 3; Table 1). The ‘first-stage’ lens antigens are formed at the 11-somite stage, shortly after the adhesion between eye-cup and presumptive lens ectoderm has been established (9 somites) and shortly before the morphological changes characterized by loss of vacuolization, nuclear orientation, and palisade phenomenon appear (13 – 19 somites).