CD4+ T Cell–Mediated Tumor Rejection Involves Inhibition of Angiogenesis that Is Dependent on IFNγ Receptor Expression by Nonhematopoietic Cells

Abstract

Immunity against MHC class II− tumors can be mediated by CD4+ T cells in the effector phase through an unknown mechanism. We show that this is IFNγ dependent but does not require IFNγ receptor (IFNγR) expression on tumor cells, T cells, or other hematopoietic cells and that IFNγR expression is not necessary in the priming phase. However, tumor immunity requires IFNγR expression on nonhematopoietic cells in the effector phase and involves inhibition of tumor-induced angiogenesis. This shows that an effective anti-tumor response involves communication between CD4+ T cells and nonhematopoietic cells, most likely within the tumor stroma, and that tumor immunity must not entirely rely on direct tumor cell killing.