Comparative ELISAs against fixed MCF-7 cells (Figure 4), which express the native MUC1 tumour antigen, gave reasonably high apparent affinity values (IgG – 3.9 × 10−9 M, recombinant Fab – 3.3 × 10−8 M, proteolytic Fab – 3.2 × 10−8 M (not shown) and scFv – 3.7 × 10−8 M), which were at least 10-fold (and approaching 100-fold) better than the peptide binding for each antibody species. The gene discussed is MUC1; the disease is neoplasm.