Volume 9 Supplement 2
Reverse signalling of membrane TNF in human natural killer cells: a comparison of the effect of certolizumab pegol and other anti-TNF agents
© Fossati and Nesbitt; licensee BioMed Central Ltd. 2011
Published: 23 November 2011
Differences have been seen among the anti-TNFs in mediating reverse signalling of membrane TNF-α (mTNF-α). Natural killer (NK) cells express high levels of mTNF-α and may be involved in rheumatoid arthritis pathogenesis. We examined the effect of certolizumab pegol (CZP) and the other anti-TNFs, adalimumab (ADA), etanercept (ETA) and infliximab (IFX), on cellular activities of NK cells.
Peripheral blood mononuclear cells from healthy volunteers were isolated and incubated in the presence of 100 U/mL recombinant human (rh) interleukin-2 (IL-2) for 20 h and 10 μg/mL anti-TNF agents or isotypic controls (human IgG1k and Fab′ PEG) for a further 4 h. Antibody-dependent cellular cytotoxicity (ADCC) was measured by loss of cell membrane integrity, by binding of 7-amino-actinomycin D to DNA. For analysis of soluble cytokine production and β-hexosaminidase release as an index of cell degranulation, NK cells were incubated with rhIL-2 and anti-TNF agents. The concentration of the soluble cytokine interferon-γ (IFN-γ) was determined by enzyme-linked immunosorbent assay. β-hexosaminidase release was quantified upon enzymatic cleavage of 4-methylumbelliferyl N-acetyl-β-D-glucosaminide in citrate buffer (0.1 M, pH 4.5) by spectrophotometric analysis.
When NK cells were incubated with anti-TNF agents in the presence of rhIL-2, IFN-γ production was significantly increased from the control level of ~84 pg/mL to ~1.1 ng/mL. All 4 anti-TNF agents stimulated NK cell degranulation, as measured by β-hexosaminidase levels, to a level of ~27% degranulation compared with a control level of 3%. ADCC measured in NK cells was detectable only with ADA, ETA and IFX (44.3%, 46.4% and 47.9%, respectively) and not with CZP (1%).
Anti-TNF agents may result in increased NK cell–mediated cytotoxicity by promoting the release of multiple cytotoxic effector molecules and inflammatory cytokines via reverse signalling through constitutively expressed mTNF-α. CZP can activate NK cells but, in contrast to conventional anti-TNFs, does not mediate ADCC due to its unique structure (lacking an Fc region).
This article is published under license to BioMed Central Ltd. This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.