CD4 and chronic obstructive pulmonary disease: While COPD often manifests in HIV-1 disease, the principal pathology is loss of CD4+ T cells, and this has been attributed to both increased CD4+ T cell death and decreased generation of new CD4+ T cells (Ribeiro et al., 2002; Dion et al., 2006; Bristow et al., 2010, 2013).