As shown in Figure 2, the immunoconjugate, tested at the concentration of 50 nM, retains the binding ability of both the parental aptamer and antibody for their targets expressed on the surface of A-431 (EGFR-positive) tumor cells and activated lymphocytes (CTLA-4-positive) [5], respectively, but it also acquires a much higher avidity for double antigen-positive SK-BR-3 tumor cells. Here, CTLA4 is linked to neoplasm.