The results of the present study suggest that CIK cell immunotherapy is able to significantly improve the immune functions of patients with cancer, showing that the proportions of the CD3+ and CD4+ T-cell subgroups were significantly increased, the activities of the NK cells were enhanced, the proportion of CD8+ cells was markedly decreased and the ratio of CD4+/CD8+ cells was normal following CIK cell immunotherapy. The gene discussed is CD8A; the disease is cancer.