Human epidermal basal keratinocytes express CDw29 antigens

Two monoclonal antibodies, K20 and 4B4, assigned to the CDw29 cluster of differentiation antigens, were shown to react with basal keratinocytes (BK). The aim of this study was to identify the antigens recognized by K20 and 4B4 on epidermal cells, and to determine whether they were identical to those found on lymphocytes. Basal keratinocyte-enriched cell suspensions were labelled with ¹²⁵I and then 1% NP40 cell lysates were used for immunoprecipitation. Under reducing conditions, K20 and 4B4 immunoprecipitated from basal keratinocytes a broad MW 105,000 band and proteins of MW 145 000, 90 000 and 80 000. Under non-reducing conditions, each band was shifted down by approximately 5000 MW. Metabolic labelling studies demonstrated that the MW 145 000 and 105 000 subunits were synthesized by basal keratinocytes. On lymphoid cells, K20 and 4B4 are known to precipitate glycoprotein complexes made on a broad MW 130 000 protein band (β subunit) associated with a protein of MW 150 000 (α subunit) and proteins of MW 90 000 and 80 000 expressed in very low amounts. The MW 145 000 and 105 000 bands immunoprecipitated by K20 from basal keratinocytes correspond to the α and β subunits present of lymphoid cells. It has recently been demonstrated that K20 recognizes the common β subunit of the very late antigens family (VLA) and that 4B4 defines the helper-inducer subset of T lymphocytes. The present investigation provides evidence that basal keratinocytes share antigens of the VLA family with lymphoid cells and that they play an important role in the immune response in the skin-immune system.