Given the result that NJB2-IL2 (2 nM affinity to EIIIB) and NJT6-IL2 (no affinity to EIIIB) elicit similar, modest delay in B16F10 tumor outgrowth after i.v. administration, we sought to understand better the design criteria for effective IL-2 immunocytokines. This evidence concerns the gene IL2 and neoplasm.