CD4 and infection: Although the CD4+ T cells in the lamina propria are considered the major target for HIV-1 (Zhang et al., 1999; Greenhead et al., 2000; Gupta et al., 2002; Guadalupe et al., 2003; Brenchley et al., 2004; Hladik et al., 2007), infection of macrophages located in the lamina propria of the intestinal, penile urethral and vaginal mucosa has been described (Shen et al., 2009; Zalar et al., 2010; Ganor et al., 2013; Josefsson et al., 2013; Yukl et al., 2014).