Osteosarcoma patients: isolation of serum antibodies by affinity chromatography

Antibodies specific for membrane-associated antigens of human osteosarcoma cells were isolated from sera of 12 patients with osteosarcoma (OS). Affinity columns were prepared by coupling purified membrane antigens from cultured human OS cell lines (TE-85 or LM) to CBrN-activated Sepharose 4B. The antigens were prepared by discontinuous sucrose gradient ultracentrifugation, papain digestion, and DEAE column chromatography. Diluted serum was passed over the affinity columns, and the adsorbed proteins were eluted with 2.5 M MgCl2 (pH 6.5). Immunodiffusion, indirect immunofluorescence, and complement fixation were used to assay antibody activity in the eluate. Specific anti-OS activity was found in the immunoglobulin (Ig) fraction isolated from the sera of the 12 OS patients, as confirmed by blocking experiments. No anti-OS antibody activity was found in sera from healthy individuals or patients with breast carcinoma, clear cell liposarcoma, or leukemia in this study. The anti-OS activity of the isolated Ig from OS patients was abolished after absorption with cultured human OS cells from lines LM, TE-85, or G292 but not after absorption with cells from lines WI-38 (embryonic lung), TE-32 (rhabdomyosarcoma), CAMA-1 or SW527 (breast carcinoma), or M-14 (melanoma). Absorption with rabbit antihuman IgG but not with rabbit antihuman IgM immunobeads completely eliminated the antibody activity.