Studies of lymphocyte stimulation to tumor-associated antigen - II. Comparison of extracts from fresh human tumors with tissue culture cell lines

Extracts of both fresh tumor and tissue culture cells propagated from these tumors were compared in a lymphocyte stimulation assay. Tissue culture lines were grown in media containing 20% fetal calf serum (FCS) and in serum-free chemically defined medium. Melanoma-associated antigens were extracted by means of 3 M KCl. Melanoma-associated antigens from two tissue culture cell lines stimulated ³H-thymidine (³H-Tdr) incorporation in lymphocytes from 7 of 17 melanoma patients, whereas no stimulation was noted in response to extracts of isologous fresh surgical specimens. The antigen solubilized from tissue culture cells demonstrated tumor-associated specificity. Stimulated ³H-Tdr incorporation was noted in lymphocytes from 17 of 38 melanoma patients, 2 of 18 patients with other cancers, and 3 of 18 normal subjects. Extracts from both FCS-grown-and chemically defined medium-grown cells were stimulatory. Fetal calf serum was detected in extracts of FCS-grown cells by complement fixation, but was not present in stimulatory concentrations. IgG antibody was detected by immunodiffusion in the nonstimulatory extract of fresh tumor, but was not detected in the stimulatory tissue culture extracts or extracts of normal tissues from the same patient.