ICOSLG and neoplasm: It has been widely proved that B7‐H2 expression on acute myeloid leukemia cells,33 bone marrow‐derived mesenchymal stem cells,34 plasmacytoid dendritic cells,35 and melanoma cells36 can promote the activation and expansion of regulatory T cells (Tregs), which contributes to immune evasion or immune suppression in tumor environments.