Figure 1.
Macrophages and mono-DCs strongly enhance BCR- but not CD40-stimulated B-cell proliferation. (A) Macrophages strongly increase BCR-activated B-cell proliferation. Macrophages were cultured with dense tonsillar B cells in the absence (□) or presence of goat anti-human IgM F(ab′)2 fragments (▪) for 72 hours. Cells were incubated for the final 16 to 24 hours with [3H]-thymidine. Incubations were performed in triplicate, and representative results are presented as the mean ± SD from 1 of 6 similar experiments. The mean fold maximal increase in BCR-induced B-cell proliferation by macrophages was 3.9 ± 1.5 in 6 independent experiments. (B) Effect of macrophages on CD40-induced B-cell proliferation. Macrophages were incubated with B cells in the absence (▵) or presence of soluble CD40L (▴), CD40 mAb (•), or an isotype control mAb (MOPC21, ○) for 72 hours. Cells were pulsed for the final 16 to 24 hours with [3H]-thymidine. Incubations were performed in triplicate, and results are presented as the mean ± SD from 1 of 3 similar experiments. (C) Dendritic cells strongly enhance BCR-activated B-cell proliferation. Mono-DCs were cultured with B cells in the absence (□) or presence of goat anti-human IgM F(ab′)2fragments (▪) for 3 days. Thymidine incorporation was quantified as described in panel A. Incubations were performed in triplicate, and data are from 1 of 3 similar experiments. The mean fold maximal enhancement of BCR-induced B-cell proliferation by mono-DCs was 4.0 ± 1.2 in 3 separate experiments. (D) Monocytes weakly increase BCR-stimulated B-cell proliferation. CD14+ monocytes were cultured with B cells in the absence (□) or presence of goat anti-human IgM F(ab′)2fragments (▪) for 72 hours. Thymidine incorporation was quantified as described in panel A. Incubations were performed in triplicate, and results are presented as the mean ± SD from 1 of 3 similar experiments. The mean fold maximal increase in BCR-induced B-cell proliferation by monocytes was 2.2 ± 1.0 in 3 independent experiments. (E) Effect of dendritic cells on CD40-induced B-cell proliferation. Mono-DCs were incubated with B cells in the presence of medium (□), CD40 mAb (•), or an isotype control MOPC21 mAb (○) for 72 hours. Cells were incubated for the final 16 to 24 hours with [3H]-thymidine. Incubations were performed in triplicate, and results are presented as the mean ± SD from 1 of 3 independent experiments.