Phenotypic characterization of five dendritic cell subsets in human tonsils

Heterogeneous expression of several antigens on the three currently defined tonsil dendritic cell (DC) subsets encouraged us to re-examine tonsil DCs using a new method that minimized DC differentiation and activation during their preparation. Three-color flow cytometry and dual-color immunohistolog y was used in conjunction with an extensive panel of antibodies to relevant DC-related antigens to analyze lin(-) HLA-DR+ tonsil DCs. Here we identify , quantify, and locate five tonsil DC subsets based on their relative expre ssion of the HLA-DR, CD11c, CD13, and CD123 antigens. In situ localization identified four of these DC subsets as distinct interdigitating DC populati ons. These included three new interdigitating DC subsets defined as HLA-DRh i CD11c(+) DCs, HLA-DRmod CD11c+ CD13(+) DCs, and HLA-DRmod CD11c(-) CD123( -) DCs, as well as the plasmacytoid DCs (HLA-DRmod CD11c- CD123(+)). These subsets differed in their expression of DC-associated differentiation/activ ation antigens and co-stimulator molecules including CD83, CMRF-44, CMRF-56 , 2-7, CD86, and 4-1BB ligand. The fifth HLA-DRmod CD11c(+) DC subset was i dentified as germinal center DCs, but contrary to previous reports they are redefined as lacking the CD13 antigen. The definition and extensive phenot ypic analysis of these five DC subsets In human tonsil extends our understa nding of the complexity of DC biology.