For example, infection of polarized T84 intestinal epithelial cells with various HIV-1 strains led to an upregulation of TNFα, which in turn led to disruption of tight junction proteins and increased permeability, and TNFα produced by HIV-1-infected monocyte-derived macrophages impaired barrier function in HT-29/B6 cells by inducing apoptosis [52, 53]. The gene discussed is TNF; the disease is infection.