ALT-803 expands and activates CD8⁺T cells. (A) The percentage of lymphocytes that were CD8⁺ T cells was not significantly altered following IV or SQ ALT-803 administration. (B) ALT-803 results in a significant increase in CD8⁺ T-cell numbers following SQ, but not IV, ALT-803 administration. (C) SQ ALT-803 administration resulted in significantly greater fold increase in CD8⁺ T cells compared with the IV route (Mann-Whitney). (D) ALT-803 resulted in T-cell proliferation detected by Ki67 expression, with a significant increase in SQ vs IV Ki67⁺ at day 7 (2-way ANOVA with Bonferroni multiple comparisons). (E-F) The number of CD4⁺ T cells and CD4⁺FoxP3⁺CD25^hi Treg cells were unchanged with ALT-803 administration. (G) CD8⁺ T cells were comprised primary of effector (E) and effector memory (EM) phenotype. (H) Frequency of Ki67⁺ CD8⁺ T cell subsets. There was a significantly greater frequency of effector memory Ki67⁺ cells at day 5 after ALT-803 compared with effector CD8⁺ T cells (paired Student t test). (I) TIM-3 expression is transiently induced on CD8⁺ T cells after ALT-803 treatment (repeated-measures ANOVA, Fisher least significant difference).