Generation and characterization of antagonistic anti-human interleukin (IL)-18 monoclonal antibodies with high affinity: Two types of monoclonal antibodies against full-length IL-18 and the neoepitope of inflammatory caspase-cleaved active IL-18

Abstract Interleukin‐18(IL‐ 18) is a pro-inflammatory cytokine that evokes both innate and acquired immune responses. IL- 18is initially synthesized as an inactive precursor and the cleavage for processing into a mature, active molecule is mediated by pro-inflammatory caspases following the activation of inflammasomes. Two types of monoclonal antibodies were raised: anti-IL- 1863−68 antibodies which recognize full-length 1−193 and cleavedIL- 18, and anti-IL- 18neoepitope antibodies which specifically recognize the new N-terminal 37 YFGKLESK 44 of IL- 18 cleavedby pro-inflammatory caspase-1/4. These mAbs were suitable for Western blotting, capillary Western immunoassay (WES), immunofluorescence, immunoprecipitation, and function-blocking assays. WES analysis of these mAbs allowed visualization of the IL- 18bands and provided a molecular weight corresponding to the pro-inflammatory caspase-1/4 cleaved, active form IL- 1837−193 , and not to the inactive precursor IL- 18, in the serum of patients with adult-onset Still's disease(6/14, 42%) and hemophagocytic activation syndrome(2/6, 33%). These monoclonal antibodies will be very useful in IL- 18and inflammasomebiology and for diagnostic and therapeutic strategies for inflammatory diseases.