ABSTRACT
Antisera produced in rabbits against homogenates of adult chicken brains and absorbed with liver and yolk were used to detect, via complement fixation, the appearance of brain antigens during development of the embryonic chick brain.
Reacting antigens are found at the earliest stages studied (stages 14–16, ca. 2 days) but remain at a low level (relative to protein) until after stage 28 (
days), when a rapid increase begins, reaching the adult level by stage 38 (12 days).Antisera were fractionated on DEAE cellulose and the anti-brain activity found in two fractions, identified as 7S and 19S respectively.
The 19S antibody reacted with a chloroform-methanol extract of adult brain homogenate but not with the residue, while the 7S antibody reacted only with the chloroform-methanol insoluble residue.
When tested against brains of embryos at different developmental stages, the 19S antibody reacted at a low and essentially unchanging level from the earliest stages studied to the adult. The 7S antibody gave no reaction with embryonic brain until after stage 28 at which time a reacting antigen was found which reached the adult level by stage 38.
Based on the appearance in detectable quantity, and the rapid accumulation, of a brain-specific protein antigen, the period between stages 28 and 38 is considered to be critical for neural differentiation.
