Histology of lymphoid organs in engrafted NOD/SCID/IL2rγ^nullrecipients. (A) The thymus showed an increased cellularity after reconstitution. (B) The thymus stained with anti-hCD3 (green) and anti-hCD19 (red) antibodies. (C) The thymus stained with anti-hCD4 (green) and anti-hCD8 (red) antibodies. The majority of thymocytes are doubly positive for hCD4 and hCD8. (D-E) Lymphoid follicle-like structures in the spleen of a recipient. (F) The lymphoid follicles mainly contained hCD19⁺ B cells (red) that were surrounded by scattered hCD3⁺ T cells (green). (G) Histology of the intestine in an engrafted NOD/SCID/IL2rγ^null recipient (left). (H) In the intestine, DAPI⁺ (4′,6-diamidino-2-phenylindole)–nucleated cells (blue) contained both scattered hCD3⁺ T cells (green) and human IgA⁺ cells (red). (I) The DIC image of the same section shows that IgA⁺ B cells were mainly found in the interstitial region of the intestinal mucosal layer. White bars inside panels represent 80 μm (C), 100μm (F), and 20μm (I).