Cancer Immunotherapy by Checkpoint Blockade

The idea that immune responses may be involved in the survival or destruction of emerging malignant cells has risen as a sort of intuition rather than a solid scientific theory. This optimistic belief arose partly from clinical observations in humans; there are rare but well-documented instances where an established, well-proven malignancy has retrogressed on its own, as in the spontaneous remission of sarcoma in patients who develop erysipelas. Somatic mutations occur constantly in the mammalian body, particularly in malignant cells, and an immune response against these new proteins was considered likely, at least theoretically. In 1960s the observation that a considerable range of systemic manifestations, apparently autoimmune in character, occur in various malignancies led to the hypothesis that malignancy-related immune responses may also involve lymphocyte clones that react to autoantigens.