Overexpression of LILRA3 downregulates secretion of many cytokines by U937 cells
Establishment of LILRA3-overexpressing U937 cells was verified at the mRNA and protein levels. As shown in Figure 3A, significant increases in LILRA3 were detected in the overexpressing U937 cells. To explore the potential effect of LILRA3 on cytokine secretion and further elucidate its role in inflammation, the supernatant of the two established cell lines were collected. Elisa assay demonstrated that the presence of LILRA3 could markedly downregulate secretion of IFN-γ (p < 0.001), TNF-α (p < 0.001), and IL-6 (p < 0.001) (Figure 3B). In view of that the LILRA3 is a soluble protein, we use LILRA3-overexpressing U937 cell lines supernate to culture the U937 cells for 12 and 24 hours, and in consistent with the previous results, we detected significantly decreased in the secretion of IFN-γ, TNF-α as well as IL-6. Cells cultured for 12 hours showed a more significant effect of inhibition (Figure 3C). Previous studies have demonstrated an anti-inflammatory role for LILRA3 based on findings that IL-10 upregulates but TNF-α downregulates LILRA3 production in vitro. Our results support the growing body of evidence that LILRA3 participates in inflammation as an anti-inflammatory molecule.