Identification and characterization of a brain-specific antigen enriched in neonatal brain. II. Antigenic stability, species cross-reactivity and tumor cell association.

NABSA is a brain-specific antigen enriched in neonatal brain. Microcomplement fixation was used to determine the extent of serological stability of NABSA towards heat denaturation and freeze-thaw denaturation. NABSA antigenic activity was progressively lost from neonatal and adult brain solutions incubated at temperatures above 40 degrees C. All activity was lost above 65 degrees C. Dilute solutions of NABSA were stable at 8 degrees C for at least two weeks and could be frozen and thawed in Tris.phosphate buffer at concentrations above 2 mg/ml with little loss of activity. NABSA was found in every vertebrate species tested. An unusually close structural similarity (a frequent characteristic of both brain-specific antigens and fetal antigens) was demonstrated by serological methods among the mammalian and avian NABSAs. NABSA was detected by microcomplement fixation analysis in 4 out of 16 rat and murine neural clonal tumor cell lines. There was no clear limitation of NABSA to a particular class of neural cell (as defined by the phenotypes of these tumor cell classes) or to rapidly dividing or stationary phase cells. NABSA may be a brain-specific oncofetal antigen (OFA-associated), since it is present in tumor cells of the nervous system and high levels are found in immature brain.