Figure 4.

Anti-interleukin-15 (IL-15) monoclonal antibody (mAb) -mediated changes in cytokine secretion levels in media from follicular dendritic cells (FDCs). The FDCs were seeded in 24-well plates (2 × 10⁴ cells/well) and anti-IL-15 mAb, or control immunoglobulin G (IgG), with GC-B cells or tumour necrosis factor-α (TNF-α), was added. GC-B cells (if present) were removed after 12 hr and the supernatants were returned to the original wells. Supernatants were harvested after an additional 24 hr and analysed by LUMINEX assay. (a) Expression levels of IL-6, IL-8, IL-16 and CCL22 in supernatants and CD54 (ICAM-1) on the surface of FDCs cultured with GC-B, and controls. IL-2, IL-4, and sCD40L were added to maintain GC-B-cell survival in the culture system. The cytokine-only (IL-2, IL-4 and sCD40L) control was included to exclude possible cytokine effects on FDCs. The amounts of IL-6 IL-8, IL-16 and CCL22 were measured with the LUMINEX assay. Values represent the concentration of each cytokine (pg/ml) in the culture media. Expression of CD54 (ICAM-1) was measured by fluorescence-activated cell sorting analysis and is represented by the mean fluorescence intensity (MFI). <LOW> values reflect samples below the range measurable by the LUMINEX assay. (b, c) Relative amount of secreted chemokines (b) and cytokines (c) when IL-15 antibody was present, shown as a percentage of the amount when the corresponding control IgG was present. Each experiment with GC-B cells or TNF-α was duplicated. Data are presented at the mean of relative cell numbers ± SD.