CD8A and neoplasm: The reason that HBc VLP vaccination shows a higher efficacy when combined with PDT might be because (1) it can improve the eradication efficiency of MC-38 tumors; (2) HBc VLPs-PDT treatment increases the number of CD45.2+ T cells and CD8+ T cells in the spleen; (3) combined treatment induced improved humoral responses in the MC-38 tumor model; or (4) the high production of immune memory T cells that resulted after combined therapeutic modality.