Thy-1 and T-cell receptor antigen expression in mycosis fungoides and benign inflammatory dermatoses.

We have studied human Thy-1 and T-cell receptor (TCR) antigen expression in mycosis fungoides and benign inflammatory dermatoses. The study included 24 biopsy specimens from 21 patients with mycosis fungoides (nine patch stage from eight patients, 13 plaque stage from 11 patients, and two tumor stage from two patients), six specimens from five patients with premycotic parapsoriasis (pre-mycosis fungoides), three specimens from three patients with lichen planus, 11 specimens from 11 patients with lupus erythematosus, 13 specimens from 13 patients with dermatitis, six specimens from six patients with drug eruptions, nine normal skin specimens from nine subjects, and three specimens from three patients with small plaque (benign) parapsoriasis. Immunoperoxidase studies using the avidin-biotin complex technique on serial frozen sections were performed. Primary antibodies were anti-human Thy-1, anti-alpha heterodimer of the TCR, anti-beta heterodimer of the TCR, and anti-delta heterodimer of the TCR. An extensive dendritic network of Thy-1+ cells was seen in all cases of mycosis fungoides. Epidermotropic cells were Thy-1 negative, and Thy-1 was expressed perivascularly in normal individuals and patients as previously reported. Epidermal gamma/delta cells were seen only in mycosis fungoides, where up to 60% of the epidermal lymphocytes expressed this TCR. The increased numbers of Thy-1 and gamma/delta T cells in mycosis fungoides were statistically significant when compared with normal skin or benign inflammatory dermatoses. The role of these dendritic dermal Thy-1+ cells and epidermal gamma/delta T cells in mycosis fungoides is unclear. The significant numbers of these potentially immunomodulating cells that were seen suggest that they are involved in the pathogenesis of mycosis fungoides.