MKI67 and neoplasm: Accessibility of the S4B6-1-IL-2 complex to the tumor mass was not an issue as the proportion of Ki67+ proliferating CD8+ T cells in the tumor significantly increased following complex administration (mean of 26.8% for non-treated versus mean of 74.6% for S4B6-1-IL-2 treated; ***P = 0.0010 by paired t test; data not shown).