IL4R and neoplasm: Immediately after arrival of tumor cells at the lungs (0–1 h post-injection), we observed that individual tumor cells arrested in the lungs had contact with monocytes at an average per hour of 2.6 ± 1 times in WT animals and 3.9 ± 2 times in IL4rα-null animals, with no significant difference between groups (p < 0.32) (Figure 3A).