A. Immunohistochemical reaction for CD4+ T-lymphocyte CD4 seen perivascularly on a lung of a C57Bl/6J mouse after a 6 month cigarette smoke exposure. × 250. B. CD4+ T-cell volume density in the lung of C57BL76J mice exposed either to room air or to cigarette smoke for 6 months and treated or not with roflumilast at 2 doses. Air = air exposure; CS = cigarette smoke exposure; R1 = treated with roflumilast at the dose 1 mg/kg po; R5 = treated with roflumilast at the dose 5 mg/kg po; N = 5 in all groups. * = p < 0.01 versus air exposed, + = < 0.05 versus smoke exposed, ++ = < 0.01 versus smoke exposed. Scale Bar = 80 μm.