Fig. 4

FDCs facilitate CD4⁺ T cell cytokine production and B cell proliferation in vitro. a Cultured FDCs were observed by optical microscopy at days 1, 7, 14, and 25. b Cultured FDCs were stained for FDC expression and analyzed by confocal microscopy, where red and blue indicate FDCs and DAPI, respectively. Images at ×40 magnification. Cultured FDCs were stimulated with the indicated reagents for 3 days and the supernatants were collected for IL-6 (c) and CXCL13 (d) detection by ELISA. Cultured FDCs were co-cultured with purified autologous CD4⁺ T cells in the presence of IL-2 (10 ng/mL) and anti-CD3/CD28 (10 μg/mL) for 3 days and the supernatant was collected for IL-21 (e) and IFN-γ (f) detection by ELISA. g Purified autologous CD19⁺ B cells were labeled with CFSE and then co-cultured with cultured FDCs in the presence of CPG (10 μg/mL) for 7 days and the proliferation of B cells was measured by flow cytometry