CD4 and neoplasm: It has been indicated that induced expression of 4-1BB by the administration of agonistic anti‐4‐1BB mAb restricts the metastasis of B16F10 melanoma cells to the lungs through increasing the population of tumor‐infiltrating lymphocytes (TIL) including CD4+ T cells, CD8+ T cells, and CD11b+ TIL in the lung tumor masses.