Abstract
An antiglioma antiserum was produced by immunization of a rabbit with membrane‐enriched preparations of a human malignant glioma cell line, LN‐18. After extensive absorption, this antiserum reacted exclusively with antigenic determinants present on seven out of 16 malignant glioma cell lines tested, as shown by complement‐dependent cytotoxicity in a ^51^Cr‐release assay. This glioma specificity could be further confirmed by quantitative absorption experiments where cells from a glioma line, LN‐135, abolished the cytolytic reactivity of the antiserum against four other glioma lines. The step‐wise absorption of the crude antiserum consisted of: step 1, absorption with normal peripheral blood lymphocytes from 10 individual donors; step 2, absorption with a pool of cells from four different lymphoblastoid cell lines and one endometrial carcinoma; step 3, absorption with cells from a colon carcinoma; and step 4, absorption with cells from two different melanoma lines. After each absorption step the antiserum was tested by complement‐dependent cytotoxicity against a large panel of malignant glioma lines and control non‐glioma cell lines. After the absorptions from step 1 and 2 the antiserum reacted with all cell lines tested, while after step 3 absorption, it reacted only with cells from malignant glioma, melanomas and fetal brain. Quantitative absorption experiments performed at this stage with fetal brain cells showed that the reactivity for fetal brain and melanoma cells could be abolished, while the antiserum was still cytolytic for malignant gliomas. After the absorption from step 4, the antiserum reacted exclusively with seven malignant gliomas. After a further absorption with normal adult brain homogenate, the antiserum still reacted with four of the seven malignant glioma cell lines. Thus, the antiserum described here recognized three types of antigens: antigens common to cells of neuroectodermal origin, antigens shared by malignant gliomas and adult brain, and antigens expressed only on some gliomas.