The role of Th2 mediated anti-tumor immunity in tumor surveillance and clearance

The concept that the immune system has the potential to recognize tumor cells and either eliminate them (tumor immune surveillance) or select for immune-resistant variants (immunoediting) has gained a resurgence of interest by the scientific community in the last decade. To date, much of the research on the immune response to cancer has focused on the response of cytotoxic CD8+ T lymphocytes to tumor-specific antigens and the production of Th1 cytokines by CD4+ and CD8+ T cells. In contrast, Th2-mediated immunity has traditionally been viewed as enhancing tumor growth, both by promoting angiogenesis and by inhibiting cell-mediated immunity and subsequent tumor cell killing. Although components of Th2-mediated immunity have been shown to promote tumor growth, there is also an expanding body of evidence demonstrating the anti-tumor activity of CD4+ Th2 cells, particularly in collaboration with tumor-infiltrating granulocytes, such as eosinophils. In this chapter we examine all the key components of type 2 immunity and their effects on tumor growth. Based on this collective data, there exists great potential for the development of Th2-mediated immunotherapies that harness the anti-tumor activity of eosinophils, alternatively activated macrophages and the antigen–IgE–receptor axis.