When the ability of the recombinant fusion protein to bind to ErbB2-positive cells was analysed by ELISA assays (Figure 4), Erb-hcAb-RNase was found to fully retain the specificity and the affinity of the parental compact antibody for mammary carcinoma ErbB2-overexpressing SKBR3 cells. Here, ERBB2 is linked to breast carcinoma.