Reovirus stimulates inflammatory cytokine production from tumour cells and immune effectors,23, 24, 25 which may potentially support CLL proliferation.26 To examine this, patient PBMCs were treated with reovirus for 7 days and expression of Ki-67 was determined; as a positive control, CLL cells were stimulated with αCD3/αCD28 microbeads to activate T cells and stimulate CLL proliferation.26 Reovirus did not increase the percentage of Ki-67+ cells or CLL proliferation (Supplementary Figure 3). Here, MKI67 is linked to neoplasm.