CD4 and cancer: Skin immunization also resulted in fewer CD8+ TIL cells expressing a high PD1 (PD1hi) phenotype (figure 7D, F), which has been linked to poor prognosis in patients with cancer.66–68 Although skin immunization did not result in a change in numbers of CD4+ T cells at the tumor margin, it resulted in significantly decreased numbers of CD4+ TIL in the tumor core (figure 7A, C).