CD8A and neoplasm: Since the percentage of tumor-killing was comparable between pretreatment of P14 CD8+ Teff cells with activated CD28WTCD8+ T cells and control P14 CD8+ Teff cells alone, the cytolytic activity of Teff cells co-cultured with activated-CD28WTCD8+ T cells was superior to Teff cells co-cultured with activated CD28KOCD8+ T cells and did not the result from enhanced tumor-killing by the former.