Blood group A-like activity in a long-term renal cell line

We evaluated two renal carcinoma lines, CAKI-1 and CAKI-2, for the presence of certain cell surface antigens. CAKI-1 was from an individual with blood type O and CAKI-2 from an individual with blood type A. A modification of the standard Chromium-51 release assay was used to determine complement dependent antibody activity in the serum of test subjects against these lines. Seventy per cent of 77 sera contained complement dependent antibody activity against CAKI-2; none was reactive against CAKI-1. Eighty-three and 88 per cent of sera from subjects with blood type B and O were reactive against CAKI-2; only 25 and 26 per cent of the sera from A and AB subjects were reactive against this same line. Both cell lines were agglutinated by anti-H lectin but only CAKI-2 was agglutinated by anti-A lectin. Fourteen of 18 normal control sera and 8 of 9 sera from cancer patients were inhibited by A antigen. A Forssman antigen obtained from guinea pig kidney removed significant complement dependent antibody activity against CAKI-2 when the sera were previously absorbed with this antigen. It would thus seem that CAKI-2 has on its surface an antigen which is either a true blood group A antigen, a Forssman antigen, or a Forssman-like antigen. Of special interest is the long persistence of this antigen in culture, thus permitting further studies characterizing its nature.