Fig. 1.
CD137 ligand interacts with CD32a to trigger reverse CD137 ligand signaling. a A total of 105 THP-1 cells were cultured in 96-well plates coated with protein or seeded with 2.5 × 104 MCF-7 cells for 24 h. IL-8 in supernatants was measured. PC: parental control. b Primary monocytes were preblocked with NT, 5 μg/ml isotype, or anti-CD32a antibody (IV.3) for 30 min before seeding onto an anti-CD137L antibody-coated plate. CD14 and CD83 expression was measured on day 7 by flow cytometry. c WT or knockout (KO) THP-1 cells were cultured on antibody-coated plates for 1 day before IL-8 in supernatants was measured. ****P < 0.0001 (two-tailed Student’s t test) versus other KO THP-1 cells. d Confocal images of surface-stained CD137L mRNA-electroporated CD137L-KO THP-1 cells. Yellow dots indicate cointernalized anti-CD32a and anti-CD137L antibodies. e WT HEK-Blue cells were transfected with CD32a-GFPSpark and/or CD137L-mCherry plasmids. Cell lysates were coimmunoprecipitated by IV.3-crosslinked agarose. The fluorescent intensity of mCherry in whole-cell lysate (WCL) and coimmunoprecipitation (co-IP) samples were measured. Representative data from at least two independent experiments are shown. NT: nontreated