Duration of Embryonic Hypersensitivity and its Relation to the Level of Differentiation of the Chick

Abstract

THE chick embryo is capable of developing hypersensitivity of the immediate type (anaphylaxis) to foreign proteins during most of its developmental life^1,2. It has also been demonstrated that, from the 12th day of incubation, sensitization of the delayed type to transplantation antigens can be elicited by injection of whole blood³. Due to the fact that chick embryos also are susceptible to immunological suppression and are not capable of humoral antibody production^4,5, a new interpretation was needed to account for such distinctive immunological properties of the chick embryo. In proposing such a theory it was postulated that, during development of the embryo, tissue-bound antibodies can be elaborated by cells derived from inactive mesenchymal precursor cells. Such tissue-bound antibodies, in common with classical antibodies, have anaphylactogenic properties¹. It was assumed that chicks, sensitized as embryos, would be capable of manifesting hypersensitive reactions for only a short time after hatching. This was based on a common observation that chick embryos and young animals injected with antigen do not manifest anaphylaxis when tested one month or more after the initial injection^4,6. The term hapto-antibody was suggested for these tissue-bound embryonic antibodies which manifest this anaphylactic property.