CD4 and viral infectious disease: Patients with the above-mentioned comorbidities and immunosuppressive therapies have common abnormalities in T cell numbers or function, the decreased total CD4+ T cell count is associated with recurrent infections, the decrease of naive CD4+T cell or natural killer (NK) cell ratio is associated with autoimmunity and decreased NK cell count in CVID patients seemed to have no association with viral infections (4, 5).