Human plasmacytoid and myeloid DCs isolated from bone marrow of mice that received transplants are functional in vitro. (A) Myeloid DCs are enriched from the bone marrow of engrafted NOD/SCID mice by depletion of mouse CD45⁺ cells and subsequent positive selection of human mDCs using BDCA-1– and BDCA-3–coated magnetic beads as described in “Material and methods.” Enriched human DCs are irradiated and plated at graded doses (ordinate axis) with allogeneic human CD4 T cells (1 × 10⁵/well). Proliferation is determined at day 5 of culture by thymidine incorporation (vertical axis). Data are representative of 2 independent experiments from 2 different cohorts of mice engrafted with CD34⁺ HPCs from different sources (cord blood or G-CSF–mobilized peripheral blood). (B) mDCs are isolated, pulsed with TT (4 LFU/mL), and plated at graded doses (ordinate axis) with autologous human CD4 T cells (1 × 10⁵/well). Proliferation is determined at day 6 of culture by thymidine incorporation (vertical axis). Data are representative of 2 independent experiments from a cohort of mice engrafted with low numbers of CD34⁺ HPCs (1.5 × 10⁶ CD34⁺ cells per animal) from G-CSF–mobilized peripheral blood. (C) Human cells are enriched from the bone marrow of engrafted NOD/SCID mice by depletion of mouse CD45⁺ cells and cultured at graded doses (ordinate axis) overnight (16 hours) with live influenza virus at low viral concentration (50 viral units based on hemagglutinin titer). Supernatants are tested for IFN-α by enzyme-linked immunosorbent assay (ELISA). Results from 2 independent experiments using mice from 2 different cohorts are shown. In experiment no. 2, 2 mice were tested. Error bars of triplicates.