RTN4R and neoplasm: Antigen-specific stimulation of GD2_tTF- and GD2_tTFmut-expressing T cells using anti-idiotype antibody ganglidiomab (Fig. 3A) or by coincubation with GD2-positive tumor targets (A4573, Kelly) (Fig. 3B) induced secretion of tTF-NGR or tTFmut-NGR, respectively.