Expression of HLA-DQ antigens on keratinocytes in Borrelia spirochete-induced skin lesions

Skin biopsies were investigated with two different immunohistochemical techniques, thus revealing HLA-DQ antigens on HLA-DR-expressing keratinocytes in the late skin manifestations of a Borrelia spirochete infection. In the early skin lesions only HLA-DR antigens were present on the keratinocytes. The invariant gamma chain of class II transplantation antigens was observed on keratinocytes in 1:5 of the late cases. Upon penicillin treatment detectable HLA-DR and HLA-DQ antigens disappeared completely from the keratinocytes. Furthermore, the mononuclear cell infiltrates dominated by anti-Leu 1 and anti-Leu 3a-reactive cells and containing many cells with markers for activation (HLA-DR, HLA-DQ, transferrin, and interleukin 2 receptors) diminished markedly. The possibility that the expression of different class II transplantation antigens on keratinocytes might reflect separate functional demands of these cells or an altered immunological reactivity in the host, is discussed. The precise functional role of the temporary expression of the class II antigens on non-lymphoid cells, however, remains an enigma.