TNF and infection: The effect of anti-4-1BB with VACV-Lister was generally similar to that observed with VACV-WR infection (three- to sixfold enhancement) and again primarily at the level of clonal expansion as production of cytokines (based on MFI) was largely comparable between the control and agonist antibody groups (Figures 3C,D, IFN-γ shown, TNF not shown).