Loss of Specificity on Passage of Immunologically Competent Cells in the Chick Embryo

Abstract

WHEN leucocytes from the blood of a fowl more than a few weeks old are placed on the chorioallantois of standard 12-day chick embryos, focal proliferative lesions are produced. These are well developed at four days and by seven days have become nodules 2–4 mm. in diameter¹. Approximately 2 × 10⁴ leucocytes produce one lesion. Owing to the occurrence of secondary foci, there may be considerable uncertainty about the count with some membranes, but when dilutions are used the distribution of counts obtained is close to a standard Poisson distribution.