Differential Influences of Fc Gamma Receptor Blocking on the Effects of Certolizumab Pegol and Infliximab on Human Monocytes.

Objectives: To compare the effects of certolizumab pegol (CZP) and infliximab (IFX) on human monocytes.Methods: Highly purified monocytes from healthy donors were cultured with CZP, IFX, control IgG1, or polyethylene glycol (PEG) at pharmacological attainable concentrations in culture medium with 10% autologous normal human serum (NHS) or with fetal bovine serum (FBS) for 24h, after which the supernatants were replaced by fresh culture medium containing LPS. After additional 24h of incubation, the supernatants were assayed for TNF- and IL-6. In some experiments, the cells were harvested after 1h of stimulation with LPS for analysis of mRNA for TNF- by quantitative PCR.Results: Pre-incubation of monocytes with CZP or IFX reduced the production of TNF- in subsequent cultures stimulated by LPS in a dose-dependent manner. The suppressive effects of IFX on the TNF- production were significantly diminished, but those of CZP were rather enhanced, in cultures with autologous NHS compared with in cultures with FBS. Addition of IgG, but not IgG F(ab)(2) fragments, significantly inhibited the suppressive effects of IFX on the production of TNF- and IL-6, whereas either IgG or IgG F(ab)(2) fragments had no significant influences on the suppressive effects of CZP. Furthermore, pre-incubation with CZP or IFX significantly inhibited the expression of mRNA for TNF- and IL-6 in monocytes compared with PEG or IgG.Conclusion: These results indicate that the mechanism of action of CZP is different from that of IFX. Thus, CZP suppresses the production of proinflammatory cytokines independently of Fc receptors, whereas the suppressive effects of IFX on human monocytes are almost totally dependent on the interaction with Fc receptors.