IDO2 and gastrointestinal stromal tumor: However, a high number of CD3+, CD8+, CD45RO+, NKp46+ and CD20+ expressing cells has been linked with favourable survival in GIST,24 CD8+ T cells may contribute to the antitumor effects of imatinib,23 and imatinib may activate CD8+ T cells and induce tumour Treg apoptosis by reducing the expression of indoleamine 2,3‐dioxygenase.25