CD4 and major depressive disorder: BD patients in hypomanic phase of the disease had significantly decreased percentage of CD4+CD25+ cells compared to patients in remission (5,64 ± 0,92 vs. 9,59 ± 0,65, p = 0,030309, ANOVA with post-hoc Tukey test) or depression (5,64 ± 0,92 vs. 9,87 ± 0,82, p = 0,019462, ANOVA with post-hoc Tukey test, Fig. 3A).