CD28 and cancer: On the other hand, the expressions of CD200, BTLA, CD28, CD27 and TIGIT in cancer patients’ CD4+ T cells were significantly lower than that of normal donors (cancer patients vs. healthy donors, 7.386 ± 0.7313% vs. 12.68 ± 1.134%, p = 0.0010; 93.48 ± 0.8471% vs. 96.95 ± 0.3344%, p = 0.0013; 88.98 ± 2.499% vs. 97.76 ± 0.6576%, p = 0.0032; 74.39 ± 4.781% vs. 94.99 ± 0.7738%, p = 0.0005; 80.95 ± 3.544% vs. 97.36 ± 0.4241%, p = 0.0002; Figure 2).