Quantitative binding of 125 I-concanavalin A to normal and transformed cells

We have measured the quantitative binding of the radioactively labeled agglutinin (125)I-concanavalin A to normal mammalian cells and simian virus 40- and polyoma virus-transformed cells from tissue culture. Parallel measurements of the amount of (125)I-concanavalin A necessary to cause agglutination of the cells in suspension were carried out. The transformed and nontransformed cells used for these experiments show large differences in their ability to be agglutinated by (125)I-concanavalin A. However, these cell lines have the same number of specific binding sites and similar affinities for the agglutinin whether transformed, trypsinized, or nontransformed. We conclude that the differential capacity of concanavalin A to agglutinate transformed cells relative to normal cells does not result from differences in the number of binding sites between the two types of cells.