AbstrAct Survival rates for metastatic lung cancer, including non-small cell lung cancer (NSCLC) and small cell lung cancer (SCLC), are poor with 5-year survivals of less than 5%. The immune system has an intricate and complex relationship with tumorigenesis;a groundswell of research on the immune system is leading to greater understanding of how cancer progresses and presenting new ways to halt disease progress. Due to the extraordinary power of the immune system—with its capacity for memory, exquisite speciifcity and central and universal role in human biology—immunotherapy has the potential to achieve complete, long-lasting remissions and cures, with few side effects for any cancer patient, regardless of cancer type. As a result, a range of cancer therapies are under development that work by ting our own immune cells against tumors. However deeper understanding of the complexity of immunomodulation by tumors is key to the development of effective immunotherapies, especially in lung cancer.