Differential expression of class II alloantigens by keratinocytes in disease.

The purpose of this study was to determine whether keratinocytes in certain disease states such as cutaneous T-cell lymphoma and lichen planus, express HLA-DR antigens (corresponding to the murine I-E antigens) only or whether they are also capable of expressing HLA-DQ antigens (analogues of the murine I-A antigens). Cryostat sections from 11 biopsies from cutaneous T-cell lymphoma and from 11 lichen planus biopsy specimens were submitted to indirect immunofluorescence and a 4-step immunoperoxidase method. This consists of applying monoclonal antibodies recognizing HLA-DR and HLA-DQ molecules and the intracytoplasmic invariant chain of the class II molecules. In 8 of the 11 cutaneous T-cell lymphoma specimens and in 3 of the 11 lichen planus biopsies concomitant expression of HLA-DR and HLA-DQ molecules by keratinocytes was detectable with the immunoperoxidase method. However, with the indirect immunofluorescence technique HLA-DQ antigens on keratinocytes could not be detected. The simultaneous expression of surface-bound HLA-DR antigens and intracytoplasmic gamma-chains was demonstrable in all cases investigated and with both the immunohistologic methods applied.