CD4 and major depressive disorder: CD4+T helper naïve cell frequencies in CMV seropositive and seronegative MDD patients and HC: In staining B the CD4+ T helper naïve (CD45RO-) cell frequency was decreased in CMV seropositive MDD patients as compared to the three other groups (Fig. 3 left and Table 2), while in seropositive HC CD4+ T helper naïve (CD45RO-) cell frequency was not decreased.