Identification and characterization of a brain-specific antigen enriched in neonatal brain. I. Developmental, regional distribution and molecular weight studies.

An antiserum raised to the 20--40% ammonium sulfate cut of the soluble proteins extracted from whole neonatal rat brain has been absorbed with liver affinity columns. The absorbed antiserum recognizes a high molecular weight antigen(s) that is (i) restricted to nervous tissue, (ii) enriched in neonatal rat brain, and (iii) present from the 17th day of gestation throughout adult life. The name given to this brain-specific antigen(s) is NABSA, short for 'neonatal-associated brain-specific antigen'. NABSA is immunologically unrelated to S-100 or 14-3-2. NABSA levels in whole rat brain increased soon after birth. The specific activity of NABSA at 2--3 days postpartum reached 3--5-fold higher levels than are found in adult brain. NABSA declined to adult levels by the 10th postnatal day, well before CNS maturation was complete. Regional variations in NABSA levels were found in the rat neonate; highest activities occurred in neonatal cerebellum. Similar variations were observed in adult brain.