CD4 and chronic obstructive pulmonary disease: Indeed, while studies showed predominance of type 1 cytokines expressed by CD4+ (T helper (Th) 1) and CD8+ T lymphocytes (T cytotoxic (Tc) 1) [5, 8, 11, 12], others described either a Th2/Tc2 [13, 14] or a Th17/Tc17 [12, 15, 16] profile in the airways, peripheral blood, and/or the broncho-alveolar lavages (BAL) of COPD patients.