IL4 and neoplasm: To assess in vivo persistence and evaluate the tumor selectivity of our 2G.4/7ICR T cells, we rechallenged animals who had initially cleared their IL4-producing tumors (Fig. 4) with 5 × 106 MDA MB 468 cells (right superior mammary fat pad) or 5 × 106 IL4-producing MDA MB 468 cells (MDA MB 468/IL4) on the left superior mammary fat pad (Fig. 5a).