Extended Data Fig. 5: LILRB3 balances NF-κB signaling with TRAF2 and SHP1/2.
a, Relative luciferase activity from THP-1-Lucia™ cells at different times after activation with anti-LILRB3 antibody or IgG (n = 3 individual samples). b, TRAF2 mRNA levels in AML cell lines and normal monocytes (n = 3 independent experiments) c, The percentage of GFP+ MLL-AF9 AML cells (with PirB knockout) expressing B3-FL or B3del ICD in peripheral blood (PB), bone marrow (BM), spleen (SPL), and liver in mice treated with PBS or LPS (n = 4 independent mice). d, Survival of mice engrafted with AML cells as treated in panel d (n = 4 independent mice). The data are presented as mean ± s.e.m, and p values were calculated by two-tailed t-test except for e by log-rank test. e, Mechanistic scheme of LILRB3 signaling. Without ligand-induced crosslinking of LILRB3, TRAF2 remains associated with LILRB3 but does not stimulate downstream signaling. When NF-κB signaling is at a low level, upon ligand-induced crosslinking of LILRB3, TRAF2 recruits cFLIP, and cFLIP is cleaved to p22-FLIP by caspase 8 (whose activity can be inhibited by zVAD-FMK). p22-FLIP binds to the IKK complex and stimulates NF-κB signaling. Meanwhile, after ligand binding to LILRB3, the ITIMs of LILRB3 are phosphorylated, which recruits SHP-1 and SHP-2. When there is a high level of NF-κB signaling stimulated by other cues (for example, LPS), higher expression of cFLIP and A20 (TNFAIP3) is induced. Increased cFLIP inhibits caspase 8 activity, and A20 disrupts the interaction between TRAF2 and LILRB3. Thus the inhibitory effect of LILRB3 on NF-κB signaling mediated by SHPs becomes dominant.
