Human Kupffer Cell Subsets Defined by CD32

Human liver myeloid cells are imperfectly defined, but it is broadly agreed that cells of stellate appearance in situ, expressing the markers CD11b and CD68, are the liver’s resident macrophages, termed Kupffer cells. Recent investigations using single cell RNA sequencing and unsupervised clustering algorithms suggest there are two populations of cells with the characteristics of tissue macrophages in human liver. We therefore analyzed dissociated human liver tissue using the markers CD11b and CD68 to define Kupffer cells and found within this population two subsets that differ in their expression of multiple surface markers. These subsets were FACS-sorted based on CD32 expression, and gene expression analysis identified them with human liver myeloid cell subsets defined by two independent single cell RNA sequencing studies. These two subsets differed in the expression of genes associated with T cell activation and immunosuppression, suggesting distinct roles in T cell tolerance. TaqMan Real-time PCR Assays with fluidigm 48x48 array platform was used in gene expression profiling. CD68+CD11b+CD32-mid or -high Kupffer cell subsets were purified from three separate human resected livers with purfusion techniques. Genes enriched in CD68+CD11b+CD32-mid or -high Kupffer cell subsets were defined by two-fold or greater in abundance compared with the expression in total livers of the same subject. Gene abundance was normalized with the arithmetic mean of ACTB, GAPDH and HPRT1. Genes enriched in Kupffer cell subsets were further compared between CD32-mid and CD32-high subsets.