Immunoperoxidase examination of cutaneous infiltrates of mycosis fungoides and large-plaque atrophic parapsoriasis with OKT10

A monoclonal antibody (OKT10), which was developed recently, reacts with pro-thymocytes, T cell acute lymphoblastic leukemia (ALL) cells, cells in normal bone marrow (including plasma cells), and activated T cells. Tissues from patients with cutaneous T cell lymphoma were studied for the presence of OKT10-reactive cells with the use of an indirect immunoperoxidase technic. OKT10-reactive cells were identified in three of eight cases of mycosis fungoides, one of two cases of Sézary syndrome, with an equivocal reaction in one of ten cases of large-plaque parapsoriasis and in one of seven positive patch tests (allergic contact dermatitis). The biologic and possible clinical implications are discussed.