iNKT cells are required to maintain CD27⁺ IgD^+/− memory B cells in culture. B cells from HDs were isolated by negative selection, cocultured with allogeneic B cell–depleted PBMCs from patients with HHV-8 MCD, and stimulated for 7 days with α-GalCer and IL-2. Alternatively, negative isolated B cells from patients with HHV-8 MCD were cultured with allogeneic B cell–depleted PBMCs from HDs. As controls, B cells from HDs were cultured with allogeneic and autologous B cell–depleted PBMCs from HDs and B cells from patients with HHV-8 MCD were cultured with autologous B cell–depleted PBMCs derived from patients with HHV-8 MCD. Cells were stained with CD19, CD20, CD27, IgD, and IgM to identify B-cell subsets. Representative flow cytometry plots of B-cell analysis showing the frequencies of CD27⁺ IgD⁺ and CD27⁺ IgD⁻ B cells at day 7 from HDs and patients with HHV-8 MCD in 2 independent experiments, HD1/HHV-8 MCD1 (A) and HD2/HHV-8 MCD2 (B).