IL4R and neoplasm: While we observed a delayed progression of 4T1 tumors in the IL‐4R KO mice, DABIL‐4 treatment was found to reduce spleen weights by only 9% (P = 0.35 vs 20% in WT; P = 0.02 in WT) and tumor weights by only 18% (P = 0.52 vs 52% in WT; P = 0.04; Fig. 4B–D).