Chemical modification and antigenicity of glioma cells

Brain tumors were induced in adult inbred Fischer rats (F-344) by systemic administration of N-methyl-N-nitrosourea mixed in the drinking water (pH 6,2). Four of these tumors, one pleomorphic glioma (78FR-G-219), two pleomorphic mixed gliomas (78FR-G-284, 78FR-G-344) and one grade I to II astrocytoma (78FR-G-299) were established in vitro and maintained as permanent cultures. The glial nature of all cell lines was ascertained by demonstrating the presence of the S-100 protein in the cultured cells. All cell lines grow as tumors when isografted in syngeneic animals. Glioma cells were conjugated with trinitrobenzene sulfonic acid (TNBS) under standard conditions. Syngeneic adult rats were immunized with TNBS-modified or unmodified irradiated glioma cells by s.c. inoculation of 1 X 10(6) cells on days 1,8 and 15. Two weeks later the animals received a s.c. booster of 5 X 10(6) native cells. Using the complement-dependent microcytotoxicity test glioma cytotoxic titers were measured 5, 6 and 7 weeks after the first immunization. The results indicated that trinitrophenylated glioma cells induced a cytotoxic antibody response against native glioma cells which was higher than that induced by untreated cells.