Cytokine release of mononuclear leukocytes (PBMC) after contact to a carbonated calcium phosphate bone cement

Human leukocytes (peripheral blood mononuclear cells, PBMC) were overlaid on calcium phosphate bone cement (CBC, Norian SRS®) and allowed to settle for 1 h under cell culture conditions. Subsequently, the cells were either left unstimulated (i.e. sham stimulation using cell culture medium), or stimulated with toxic shock syndrome toxin-1 (TSST-1, 10 ng/mL), staphylococcal enterotoxin B (SEB, 10 ng/mL), or concanavalin A (ConA, 2 μg/mL) for further 24 h using cell culture conditions. Supernatants were then analyzed for cytokine content (interleukin-1 receptor antagonist, IL-1ra; IL-2; IL-6; IL-10; IL-12) by enzyme-linked immunosorbent assay. While the spontaneous generation of cytokines was not influenced, the IL-2 release from stimulated PBMC was significantly decreased in contrast to other analyzed cytokines after contact to the curing CBC compared to control incubations without CBC. This decrease in IL-2 release was not due to known inhibitors of IL-2 synthesis platelet factor-4 (PF-4), IL-10, TGF-β, or elevated calcium ion concentrations.