The immunological response of foetal mice to influenza virus.

Since the introduction of the "self-marker" hypothesis of antihody production by Burnet and Fenner (1949) and the experiments of Billingham, Brent and Medawar (1953) on the production of actively acquired tolerance in mice to skin homografts from a different strain, there has been a great deal of interest in the immunological behaviour of animals exposed in utero to a variety of antigens. Burnet and Fenner predicted that an antigen introduced into the circulation of a developing animal before a critical phase in the maturation of the antibody-producing system would come to be recognized as "self'. In consequence, the animal's capacity to produce antibody to that antigen would be permanently impaired. Early attempts to produce experimental support for this hypothesis were unsuccessful (Burnet et al., 1950). However, since then, several workers have reported the induction of tolerance to antigens giving rise to classical circulating antibody. Hanan and Oyama (1954) have induced immunological tolerance in rabbits to bovine serum albumen by neonatal injections and this work has since been confirmed and extended (Cinader and Dubert, 1955). Buxton (1954) has reported the induction of tolerance in chicks to Salmonella puUorum by the intravenous injection of a killed vaccine into embryos. Kerr and Bobertson (1954) noted that calves given Trichomonas foetus antigen early in'life never were able to produce antibody to this agent. However, negative reports have also been quite numerous (Bauer et al., 1956; Burnet et al., 1950; Owen, 1956).