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

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Abstract
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 3H-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 3H-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.

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