CD24a expression levels discriminate Langerhans cells from dermal dendritic cells in murine skin and lymph nodes

Langerhans cells (LCs) and dermal dendritic cells (dDCs) are the professional antigen-presenting cells of the skin. Recently, their immunogenic versus tolerogenic role has come under re-investigation. LCs are distinguished from dDCs by Langerin (CD207) staining or by detection of Birbeck granules. However, for in vitro experiments it is desirable to have a simple and robust flow cytometric demarcation of both cell types. We show here that CD24a is expressed on LCs but not on dDCs isolated directly from the skin. Moreover, in combination with major histocompatibility complex class II (MHCII), CD24a expression levels distinguish LCs from dDCs in skin-draining lymph nodes after antigen activation and migration. High expression of CD24a correlated strictly with CD207 expression. MHCIIhigh cells were unique for skin-draining lymph nodes and were shown to be the only cells carrying antigen after FITC painting of the skin. CD24a expression levels further differentiated LCs and dDCs in the MHCIIhigh population. As staining for CD24a does not require fixation of cells, CD24a-stained cells can be used for in vitro experiments to analyze and compare the functional roles and properties of dDCs and LCs.