Taken together, the fusion proteins C595scFv-Fc and C595scFv-Fc-IL2 specifically bind to MUC1-positive tumour cells via the anti-MUC1 scFv domain, the C595scFv-Fc-IL2 protein binds in addition via IL2 to CD25+, activated lymphocytes in vitro. The gene discussed is IL2; the disease is neoplasm.