Fig. 1 Histological analysis of human Sk-LN grafts of SCID-hu IC mice, 3 months after transplantation. a and d, Paraffin-embedded sections stained with hematoxilin eosin; original magnification,× 100. b, c, e and f, Frozen sections immunostained with irrelevant control monoclonal antibody (b and c) or monoclonal antibody against human follicular dendritic cell (e and f) followed by hematoxylin counterstaining; original magnification,× 400. Sk-LN grafts transplanted into SCID-hu BM/Thy mice are massively infiltrated with leukocytes (d) and contain well-defined networks of follicular dendritic cells (red staining in e), resembling the structures in human fetal spleen (red staining in f). There are only small amounts of leukocyte infiltration in human skin grafts transplanted into control SCID mice (a). Isotype control stainings for the SCID-hu Sk-LN graft (b) and fetal spleen (c) do not show substantial staining. a b c d e f