HLA class I antigen (heavy and light chain) expression by langerhans cells and keratinocytes of the normal human epidermis: ultrastructural quantitation using immunogold labelling procedure.

Using an immunogold labelling procedure, we quantified the density of major histocompatibility (MHC) class I antigens on the surface of Langerhans cells (LCs) and keratinocytes of the normal human epidermis. According to ultrastructural features, keratinocytes were divided into three subpopulations: stratum basalis (SBK), stratum spinosum (SSK), and stratum granulosum keratinocytes (SGK), and analyzed separately. For this purpose, three monoclonal antibodies (MCAs) were employed: an anti-HLA A,B,C, an anti-B-microglobulin (B-m), and a polymorphic anti-HLA A2 Aw69 MCA. Under electron microscopy, quantitative analysis demonstrated: (a) the presence of a high amount of HLA monomorphic determinants on SBK and SSK and moderate but significant labelling of SGK; (b) the very weak density of MHC class I antigens on the surface of epidermal LCs; (c) the expression, at an identical level, of the HLA heavy chain common determinant (HLA A,B,C), B-m, and the alloantigen HLA A2 by all epidermal cells (ECs) apart from SGKs and LCs that presented far fewer HLA A2 sites than monomorphic determinants (B-m and HLA A,B,C); (d) the absence of HLA class I on corneocytes and a moderate labelling of melanocytes. A knowledge of the precise quantitative distribution of HLA class I antigens among various cell subpopulations of the normal human epidermis would be very useful for the study and followup of cutaneous malignancies that are known to lose these molecules as well as for the understanding of immune responses, especially allospecific, that involve the skin. [ABSTRACT FROM AUTHOR]