Expression of OKM5 antigen on human keratinocytes in positive intracutaneous tests for delayed-type hypersensitivity

Antigenic characteristics of human keratinocytes (HK) were studied in positive intracutaneous tests for delayed-type hypersensitivity in vivo using murine monoclonal antibodies against human OKM5, OKM1, OKT6, Leu-7 and HLA-DR antigens and compared with those of negative skin reactions. By contrast to negative intracutaneous tests, keratinocytes displayed both OKM5 and HLA-DR antigens in all positive skin reactions above the dermal inflammatory infiltrate. OKM5 recognizes an 88-kilodalton cell surface determinant of monocytes, which could also be induced in vitro in keratinocytes upon incubation with gamma-interferon. We demonstrate here for the first time that the expression of this macrophage marker can also be induced in vivo in the HK.