Tissue typing of cells in culture. IV. Cell surface antigens of tumor cell lines, not obviously belonging to the HLA-system.

Studies on the HLA pattern of several human tumor cell lines by the mixed hemadsorption test and also studies on the discriminative patterns formed by a collection of sera on a number of cell lines and diploid cells have been reported elsewhere. It was noted during these studies that some sera reacted in a fashion indicating that they did not represent any of the HLA-A or -B series and probably not the HLA-C series either. The corresponding antigenic determinants were tentatively designated Ek-1 to Ek-11. The pattern of these antigens among the cell lines is given in a table and it seems apparent that the Ek-series considerably increases the cell identification potential of the typing results. So far, five of the sera determining the Ek-antigens have failed to be blocked by anti-beta-2-microglobulin, indicating that the antigens do not belong to the HLA-A, B or C series. Preparatory work for HLA-D typing is under way.