Like many medical advancements, the rise of cancer immunotherapy has not been linear. As early as the 1960s, it was hypothesizedthat the body could target specific immune system structures such as cytokines, and Tcells could function to inhibit the development of cancer cells and possibly prevent them. This theory gave rise to the development of monoclonal antibodies (mAbs) for therapeutic uses in the 1970s. However, these early successes were limited. The immune responses provoked were not lasting, and many proved to be toxic. What did become apparent was that science lacked a proper understanding of relevant immune system mechanisms.