CXCR4 and HIV infectious disease: Since human hepatocytes express the HIV chemokine co-receptor CXCR4 on the surface, [15] and since HIV gp120 treatment of immune cells [6], [16] increases TRAIL receptor expression, we questioned whether soluble HIV gp120, that is present during HIV infection, can signal through CXCR4 on the surface of human hepatocytes and also increase TRAIL receptor expression on the surface of the cell.