Development of lymphocytes in NOD/SCID/IL2rγ^nullrecipients. (A) The flow cytometric analysis of human T cells in recipients. The majority of cells in the thymus were hCD4⁺hCD8⁺ double-positive thymocytes (top). The CD3⁺ spleen cells contained hCD4⁺ or hCD8⁺ single-positive mature T cells (bottom). (B) hCD34⁺hCD19⁺ pro-B, hCD10⁺hCD19⁺ pre-B, and hCD19⁺hCD20^hi mature B cells were seen in different proportions in the bone marrow and the spleen of recipient mice. Numbers represent percentages within total nucleated cells. (C) B cells expressing each class of human immunoglobulin heavy chain were seen in the bone marrow, the peripheral blood (PB), or the spleen of engrafted NOD/SCID/IL2rγ^null mice. Numbers represent percentages out of nucleated cells.