TAT and HIV infectious disease: Among these, two of great relevance include demonstrations that (1) the binding and clustering of Tat molecules by HSPGs occurs at low-micromolar concentrations [18] and (2) a quaternary complex containing Tat homodimers with two HSPGs (HS/Tat–Tat/HS) are physiologically assembled in order to promote adhesion, migration, and extravasation of lymphocytes across the endothelium during HIV infection [17].