Protein‐A antibody‐binding (PAAB) technique for detection of tumor‐associated membrane antigen (TAMA) of lewis lung carcinoma

Xenoantisera were prepared in rabbits against intact paraformaldehyde‐fixed Lewis lung carcinoma (LLCa) cells and membrane solubilized proteins extracted with Triton X‐100 and 3M KCI. The antisera were analyzed for antibodies to tumor‐associated membrane antigens (TAMA) by means of a solid‐phase radioimmunoassay (RIA). The immunoassay employed 125I‐labelled Staphylococcus aureus protein A (SPA) to detect specific antibody binding to glutaraldehyde‐fixed Lewis lung tumor target cells. The protein‐A antibody‐binding (PAAB) method is rapid, sensitive and reproducible. The PAAB revealed a possible LLCa‐TAMA as evidenced by the reactivity of xenoantisera raised to LL paraformaldehyde tumor cell vaccine (TCV) and LL tumor Triton X‐I00 (TTri) and 3M KCI (TKCI) extracts of membrane preparations. The reactivity of our antisera followed linear dose‐response kinetics but the degree of reactivity decreased from anti‐TCV to anti‐TTri to anti‐TKCI respectively. The LL‐TAMA demonstrated specificity since our antisera did not significantly cross‐react with normal C57BL/6 cellular antigens or other known murine tumor‐associated surface antigens of virally and chemically‐induced tumor systems.