Expression and DC-mediated induction of AID in primary MM cells. (A) IHC detection of AID expression in primary MM cells. Serial sections were stained with anti-AID (i) and anti-CD138 Ab (ii). Panels iii and iv show higher magnification (×40) images. Panel v shows the presence of DC-SIGN⁺ DCs interdigitating within tumor cells in the same marrow. (B) Purified CD138⁺ MM cells were cultured alone or with DCs as in Figure 1A. After overnight culture, tumor cells were re-isolated and analyzed for the expression of AID. Data are representative of ≥ 3 similar experiments. (C) DC-SIGN⁺ subpopulation of the DCs were isolated from the BM and cocultured with CD138⁺ tumor cells. After overnight culture, tumor cells were re-isolated and analyzed for the AID expression. Data are representative of 2 independent experiments.