In an adoptive therapy model of lymphoma, self-antigen-specific T

In an adoptive therapy model of lymphoma, self-antigen-specific Teff cells were potentiated by even a modest reduction of CTLA4. A subtle reduction of CTLA4 did not curtail Treg-cell suppression. Thus, Teff cells had an exquisite sensitivity to physiological levels of CTLA4 variations. However, both Treg and Teff cells were impacted by anti-CTLA4 antibody blockade. Therefore, whether CTLA4 impacts through Treg cells or Teff cells depends on its expression level. Overall,

the results suggest that the tumor microenvironment represents an “immunoprivileged self” that could be overcome practically and at least partially by RNAi silencing of CTLA4 in Teff cells. A cardinal capacity of the immune system is to differentiate between “self”, the body’s own tissue, and “non-self”, exemplified by microbial infectious agents. Malignant tumor tissues present a distinct challenge to the immune system as “altered self”. Antigenic proteins from mutated genes in cancer cells, or viral products from transformed tumor cells, may trigger the immune system as tumor-specific

antigens ICG-001 (TSAs) that are not expressed by nonmalignant tissues. However, for the vast majority of tumors, TSA have yet to be identified. Well-studied tumor-associated antigens (TAAs) are in fact self antigens associated with cellular differentiation [1]. The difficulty to identify TSA compels a supposition that cancer cells are largely “self”. The premise of cancer cells as “altered self” would predict the well-recognized association of autoimmune risk with cancer immunotherapy [2]. On the other hand, the “altered self” view could also foretell autoimmunity as a beneficial effector to destroy cancer cells. In other words, although autoimmunity and tumor immunity are often viewed as being on opposite sides of the same coin, they could

also be viewed to be on the same side of the coin, serving as overlapping mechanisms for tumor destruction. Indeed, the remarkable benefits of cancer immunotherapies showed in recent immunotherapy Fenbendazole trials, most notably anti-CTLA4 antibody blockade, often came with the price of autoimmune adverse effects [3]. The intricate tangle of auto-immune toxicity and antitumor immunity substantially affects the benefit/risk ratio calculation in immunotherapies [1]. On the other hand, auto-immunity may serve to benefit clinical management of cancers. Evidence gathered from the clinics treating a variety of cancers with immunotherapies based on IL-2 [4], interferon α-2b [5], or CTLA4 [3, 6] suggests that the therapy-induced autoimmunity, at least in part, may actually mediate the destruction of cancer cells. The clinical observations provoke suggestion of a paradigm shift, to which autoimmunity is not a shunned side effect, but instead an acceptable or even desirable antitumor mechanism [7].

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