MRC1 and periapical periodontitis: Veloso et al. (36) evaluated macrophage expression of cluster of differentiation 14 (CD14), 64 (CD64), 80 (CD80), 163 (CD163), and 206 (CD206) in symptomatic apical periodontitis (SAP) and asymptomatic apical periodontitis (AAP) using flow cytometry.