The i antigen complex: A new specificity unique to dividing human cells

Evidence is presented that erythroagglutinin, anti‐i, sera recognize a membrane antigen characteristic of dividing human cells. The antigen was present on fetal tissues, cultured cell lines and mitogen‐stimulated lymphocytes and absent from normal adult tissues. Cell synchrony studies with cultured lymphoblasts indicate that antigen expression is maximal during the S and G 2 phases of the cell cycle. Absorption studies have shown that antibodies to this determinant are distinct from the erythroagglutinin activity of sera. The significance of “division antigens” in relation to oncofetal antigens is discussed.