CD4 and cancer: Briefly, cancer patients with high numbers of baseline tumor-infiltrating total CD4+ T cells, Th1 CD4+ T cells, CD8+ T cells, the ratio of CD8+ T cells/CD4+ T cells, T follicular helper-T cells (Tfh), Th1, Th9, and Th17 CD4+ T cells respond better to anti-PD-1 immunotherapy, whereas an inverse predictive value was observed in patients with high levels of infiltrating regulatory T cells or Th2 CD4+ T cells [226,231].