What is Tumor-infiltrating lymphocytes?

Tumor-infiltrating lymphocytes are white blood cells that have left the bloodstream and migrated towards a tumor. They include T cells and B cells and are part of the larger category of ‘tumor-infiltrating immune cells’ which consist of both mononuclear and polymorphonuclear immune cells, in variable proportions. Their abundance varies with tumor type and stage and in some cases relates to disease prognosis

TILs can often be found in the tumor stroma and within the tumor itself. Their functions can dynamically change throughout tumor progression and in response to anticancer therapy

TILs are implicated in killing tumor cells. The presence of lymphocytes in tumors is often associated with better clinical outcomes.