CD163 positive subsets of blood dendritic cells: The scavenging macrophage receptors CD163 and CD91 are coexpressed on human dendritic cells and monocytes

Abstract

CD163 and CD91 are scavenging receptors with highly increased expression during the differentiation of monocytes into the anti-inflammatory macrophage phenotype. In addition, CD91 is expressed in monocyte-derived dendritic cells (MoDCs), where the receptor is suggested to be important for internalization of CD91-targeted antigens to be presented on the dendritic cell surface for T-cell stimulation. Despite their overlap in functionality, the expression of CD91 and CD163 has never been compared and the expression of CD163 in the monocyte-dendritic cell lineage is not yet characterized. CD163 expression in dendritic cells (DCs) was investigated using multicolor flow cytometry in peripheral blood from 31 healthy donors and 15 HIV-1 patients in addition to umbilical cord blood from 5 newborn infants. Total RNA was isolated from MACS purified DCs and CD163 mRNA was determined with real-time reverse transcriptase polymerase chain reaction. The effect of glucocorticoid and phorbol ester stimulation on monocyte and dendritic cell CD163 and CD91 expression was investigated in cell culture of mononuclear cells using multicolor flow cytometry. We identified two CD163 + subsets in human blood with dendritic cell characteristics, CD163 lo and CD163 hi, together constituting a substantial fraction of DCs. Both subsets were characterized as [lin] −CD4 +ILT3 +HLA-DR +CD11c + by flow cytometry, and CD163 mRNA was readily detectable in MACS purified human DCs. CD163 on DCs was upregulated by glucocorticoid, and treatment by phorbol ester significantly decreased surface expression. Overall, the expression of CD163 on DCs was significantly increased in HIV-1 patients (19.3% [95% CI: 14.7–26.3%]) compared to healthy patients (10.5% [95% CI: 8.0–12.5]) p < 0.001 . The CD163 lo subset was CD16 +, whereas the CD163 hi subset was CD16 −. Both subsets were CD91 +, thereby constituting a subfraction of the recently described CD91 +CD11c + dendritic cell subset. Coexpression of CD163 and CD91 was also demonstrated on human monocytes, which upon glucocorticoid treatment exhibited an increase in both CD163 and CD91 expression. We have now shown that CD163 and CD91 are coexpressed and coregulated on human monocytes. In addition, two subsets of CD163 + DCs constituting a fraction of the recently described CD91 +CD11c + dendritic cell subset have been identified. The CD163 expression pattern suggests that if antigens are targeted to CD163 they may induce an immunostimulatory response like that of CD91-targeted antigens.