As observed previously [5], treatment of Colo26-HA tumors with immune-enhancing PDT regimen resulted in significantly increased numbers of activated and proliferating CD8+ T cells (P ≤ 0.01), while treatment with the tumor-controlling PDT regimen had minimal effect on the numbers of activated CD8+ T cells compared to CD8+ T cells isolated from animals treated with HPPH alone (P ≤ 0.2; Fig. 3a). Here, CD8A is linked to neoplasm.