Interleukin 2-like material in human epidermis: a ligand for the human interleukin 2-receptor 55 kD alpha chain

The antirecombinant interleukin 2 (rec-IL-2) monoclonal antibody (moAb) 15.2 cross-reacts with a skin antigen located at the cell surface of human keratinocytes within the granular layer. This study extends the analysis of this IL-2-like material to its reactivity with eight antibodies raised against natural IL-2, rec-IL-2 or IL-2 peptides. Four among them were found to react with the granular epidermal layer as well as with a simian virus 40 (SV40) transformed human keratinocyte cell line. Each of these four antibodies gave similar labeling patterns, although with different intensities, and competitively inhibited each other. Analysis at the messenger RNA level in epidermal cells and SVK 14 also indicated that this material is very likely different from IL-2. From the knowledge, for some of these antibodies, of the amino-acid regions they recognize on the IL-2 molecule, it is inferred that the skin antigen shares with IL-2 at least two overlapping epitopes located in the 33-54 amino-acid region of IL-2, a region that has been shown to be involved in the binding of IL-2 to the IL-2-receptor (IL-2-R) 55 kD chain. Indeed, a purified recombinant soluble species of this IL-2-R is shown in this study to bind specifically to the IL-2-like skin material. As far as IL-2-R bearing cells are found in normal epidermis (Langerhans cells) and as important infiltrates of IL-2-R positive T lymphocytes are often encountered in cutaneous diseases, a potential role for this IL-2-like material in skin immunophysiopathology is suggested.