TNFRSF11A and periapical periodontitis: When comparing the percent of RANK+ cells in THP-1 vs. PBMC from patients with apical periodontitis, we observed an increase in %RANK+ cells when α-IRAK-4 was added to PBMC in comparison with THP-1 when α-IRAK-4 + E.f. and α-IRAK-4 + LTA were added (13.6%, 10.6–18.5%; 2.96%, 2.08–4.82%; 3.67%, 3.09–8.35%, median and interquartile range, respectively), as depicted in Figure 4A (p < 0.05).