Second, the presence or absence in tumours of specific γδ T cell subsets (such as Vδ1 or Vδ3) may help to define patients who are responsive or unresponsive to ICB, respectively, especially in the case of MMR-d cancers and other malignancies with frequent HLA class I defects, such as stomach adenocarcinoma39 and Hodgkin’s lymphoma40. The gene discussed is MRC1; the disease is cancer.