Tumor infiltrate was mainly characterized by CD4+ T cells, and the average number of CD4+ T cells was 16-fold higher in GL261 tumors in pre-vaccinated mice as compared to GL261 tumors in non-vaccinated mice (CD4+: 2,622 cells/mm2 in challenged GL261; CD4+: 153 cells/mm2 in GL261). Here, CD4 is linked to neoplasm.