Histology and ultrastructure of cultured human tumor cells exposed to antisera to the nerve growth factor.

Various dilutions of anti-nerve growth factor serum from rabbits or horses immunized with purified nerve growth factor were added to rapidly growing, 48-hr monolayer cultures of a human glioblastoma (C356) and of an H. Ep. 2 cell line. Cytotoxic effects, beginning 2 hr later and usually progressing to complete cell death at 17 hr, were studied in vitro in stained coverslip preparations and by electron microscopy. Antiserum made in the horse had about one-fifth the cytotoxic activity shown by antiserum made in the rabbit, which was 50% cytocidal at a concentration of 0.75% in the culture medium. H. Ep. 2 cells were about 5 times as resistant as C356 cells. In both cell lines, many of the cells surviving the antiserum showed nuclei with generally intact membranes, containing 20 to 50 or more rounded chromosome-like bodies, suggesting prophase mitotic activity. Control monolayers receiving normal rabbit or horse serum were comparable to the untreated controls (grown in Eagle's minimal essential medium