CD4 and disease arising from reactivation of latent virus: Compared with IEC-stimulated CD4 + T cells without PMA/I, PMA/I treatment significantly increased GFP expression in IEC-stimulated T cells (Fig. 5B, p = 0.0003 for both IEC − and IEC + stimulated T cells), demonstrating that latent infection was present in activated CD4 + T cells stimulated by IEC − and IEC +.