ITGA4 and neoplasm: Our previous studies used methotrexate-packaging T-MPs (MTX-MPs) to treat MPE in patients.26,28 We found that MTX-MPs recruit a large number of CD11b+CD15+CD49d– neutrophils (78% MPE cells) to the malignant fluids, which not only display tumor cell-killing effect but also release neutrophil extracellular traps to the damaged epithelium.28 Apart from neutrophils, macrophages are commonly present in untreated malignant fluids.29 In this study, we further analyzed macrophages in the treated patients’ MPE in order to illuminate the impact of drug-MPs on the macrophages.