Induction of Immunological Tolerance in Rats to Foreign Erythrocytes

Abstract

THE term ‘acquired immunological tolerance’ was used by Medawar and co-workers¹ for describing the toleration of skin homografts in mice which had been injected in utero with a cell suspension from mice of the donor strain. Since then, many workers have tried to produce a similar tolerance to antigens which give rise to antibodies of the classical circulating type. Both positive^2–4 and negative^5–7 attempts have been reported. One of the systems that has been investigated recently is the anti-sheep erythrocyte system. Bauer et al. ⁷ have reported failure to produce immunological tolerance in rats by intra-uterine injection of fœtuses with sheep red cells. They point out that in many of the successful experiments quoted above, large doses of antigens had to be injected for prolonged periods to produce non-reactivity. They maintain that the whole range of phenomena included under the heading of immunological tolerance may well be an expression of the phenomenon of immune paralysis, such as can be produced by the injection of pneumococcal polysaccharides into mice⁸.