A tumour-associated antigen from the pleural effusion of patients with squamous-cell carcinoma of lung.

A fraction showing tumour-associated antigenic properties has been isolated from pleural effusions of patients with squamous-cell carcinoma of the lung. Purification of the material was accomplished by ion-exchange and affinity chromatography, and by immunoabsorbents. The antigenic activity was monitored by its inhibitory capacity in a specific complement-dependent cytotoxic system. The final fraction has a mol. wt. of approximately 1.7 X 10(5), as judged by gel filtration on Sephadex G200, and the main component appears to be a glycoprotein with N-acetyl-D-glucosamine groups. The most purified antigen preparation exhibited a highly selective capacity to inhibit in the cytotoxic assay and to bind, when labelled with 125I, to 2 specific antisera. The active fractions isolated from pleural effusions fully crossreacted with fractions prepared from squamous-cell carcinoma extracts. CEA and bacterial antigens were not detected in the material, and the presence of alpha-fetoprotein, HLA and blood-group antigens may be ruled out on account of their respective molecular weights.