PECAM1 and HIV infectious disease: HIV infection in particular profoundly perturbs the architecture of lymphoid organs through progressive collagen deposition and fibrosis, that disrupts and damages the important follicular reticular cell (FRC) network (13, 67) To map stroma and GC specific changes we developed a panel consisting of markers CD31, IgD, CD20, FDC, Ki67, Collagen I and Collagen IV (Figure 6A).