Deciphering the fate of slan+-monocytes in tonsils by gene expression profiling

slan+-monocytes represent a subset of the “non-classical” CD14dim/-CD16++ monocytes, which are characterized by the expression of the so-called “slan” antigen, recognized by specific monoclonal antibodies. slan+-cells can be identified in peripheral tissues including tonsils. However, their origin from slan+-monocytes as well as their terminal differentiation state (toward macrophages/dendritic cells) were only partially resolved. In this study, we performed transcriptomic studies of tonsil slan+-cells,CD1c+DCs/DC2 and CD11b+ CD14+macrophages, as well as subsets of peripheral blood monocytes and we report that tonsil slan+-cells mainly represent macrophage-like cells with features distinct from those of tonsil CD11b+CD14+macrophages or CD1c+DCs/DC2.  Moreover we provide a number of molecular evidence indicating that tonsil slan+-cells derive from peripheral slan+-monocytes. Tonsil slan+-cells, CD1c+DCs/DC2 and CD11b+ CD14+macrophages, as well as peripheral DC2, “classical” (CL) CD14++CD16- monocytes, “intermediate” (INT) CD14++CD16+ monocytes, “non-classical” (NC) CD14dim/-CD16++ monocytes and slan+-monocytes were isolated by cell sorting. Total RNA was then extracted and subjected to Smart-seq2 protocol for transcriptomes analysis