Antigen‐presenting capacity in normal human dermis is mainly, subserved by CDla + cells

Summary A proposed role for antigen‐presenting dermal dendrocytes in the pathogenesis of many dermal inflammatory skin diseases remains speculative. We therefore sought to determine the phenotype and functional characteristics of antigen‐presenting cells isolated from normal human dermis. Normal adult human skin was incubated overnight with dispase at 4°C, the epidermis was removed, and the residual dermal preparation was then minced and digested with a mixture of hyaluronidase, collagenase, and DNAase at 37°C, prior to filtration through mesh. Dermal cell suspensions thus obtained were stained using specific monoclonal antibodies, and analysed by fluorescence micro‐ scopy or flow cytometry. Mean values were as follows: CD45 + leucocytes 39%, HLA‐DR + cells 39%, Ulex europaeus agglutinin I + endothelial cells 26%, CD1a + cells 3.9%, CD11b + cells 16%, CDllc + cells 6%. Mitomycin C‐treated crude dermal cell suspensions induced allostimulation of peripheral blood mononuclear cells in a 7‐day culture, as assessed by 3 H‐TdR incorporation. Depletion of CDla + Langerhans‐like cells from the dermal cell preparation, by 95, 74 and 90% in three separate experiments using immunomagnetic beads, reduced 3 H‐TdR incorporation at optimal responder‐to‐ stimulator cell ratios by 90, 64, and 87%, respectively. Our findings suggest that, in normal human dermis, the great majority of the alloantigen‐presenting capacity resides in the CDla + Langerhans cell‐like dendritic antigen‐presenting cell population, and not to any great extent in either CDla − macrophage‐like cells, or HLA‐DR + endothelial cells. The relationship of the CDla + dermal antigen presenting cells to the Langerhans cell lineage remains to be determined.