Unfortunately, whole killed cell vaccines have not been very successful in activating a specific CTL response. Approaches have been proposed to by-pass the need for helper T cells by providing cytokines for T cell growth and activation. One method uses biodegradable microspheres to release encapsulated cytokines over a long period of time. Another method involves transfecting autologous or allogeneic tumor cells with genes coding for cytokines and injecting them into patients. Some cytokines also possess the ability to trigger a nonspecific inflamatory response which itself possesses anti-tumor activity.
Many clinical trials employing cytokines are currently underway.
There are however toxic side effects in patients to high doses since IL-2 also stimulates the production of more cytokines. TNF TNF has high antitumor effects, however high doses can yield highly toxic effects. Local injections of TNF is used to treat limb sarcomas and in these cases, venoue blood return from the limb is decreased during administration to decrease systemic effects. These cytokines stimulate the maturation of granulocyte precursors. An interesting finding in using transfected tumor cells expressing cytokines in animal models is that specific T cell immunity to these transfected tumor cells imparted immunity to these animals in subsequent challenges of non-transfected tumor cells of the same type.