Expression profile of novel cell surface molecules on different subsets of human peripheral blood antigen-presenting cells

Although major steps have been recently made in understanding the role of the distinct subsets of dendritic cells (DC)/antigen-presenting cells (APC), further studies are required to unravel their precise role, including in-depth immunophenotypic characterisation of these cells. Here, we used eight-colour flow cytometry to investigate the reactivity of a panel of 72 monoclonal antibodies (including those clustered in seven new Cluster of Differentiation, CD) on different subsets of APC in peripheral blood (PB) samples from five healthy adults. These experiments were performed in the context of the Tenth International Workshop on Human Leukocyte Differentiation Antigens (HLDA10). Plasmacytoid DC was the only cell population that expressed CD85g and CD195, whereas they lacked all of the other molecules investigated. In contrast, myeloid DC mostly expressed inhibitory C-type lectin receptors (CLRs) and other inhibitory-associated molecules, whereas monocytes expressed both inhibitory and activating CLRs, together with other phagocytosis-associated receptors. Within monocytes, progressively lower levels of expression were generally observed from classical monocytes (cMo) to SLAN(−) and SLAN(+) non-classical monocytes (ncMo) for most of the molecules expressed, except for the CD368 endocytic receptor. This molecule was found to be positive only in cMo, and the CD369 and CD371 modulating/signalling receptors. In addition, the CD101 inhibitory molecule was found to be expressed at higher levels in SLAN(+) vs SLAN(−) ncMo. In summary, the pattern of expression of the different signalling molecules and receptors analysed in this work varies among the distinct subsets of PB APCs, with similar profiles for molecules within each functional group. These findings suggest unique pattern-recognition and signalling capabilities for distinct subpopulations of APCs, and therefore, diverse functional roles.