Toll-like receptors 2, 4 and 9 expression in cutaneous T-cell lymphoma (mycosis fungoides and Sézary syndrome).

The aim of this work was to study Toll-like receptors (TLRs) 2, 4 and 9 expression patterns in parapsoriasis and in cutaneous T-cell lymphoma (CTCL): Mycosis fungoides (MF) and Sézary syndrome (SS) at different stages of the illness. The expression of TLRs was examined by immunohistochemistry on paraffin-embedded biopsies. Normal skin, atopic dermatitis and psoriasis, were used as controls. In cutaneous lesions of inflammatory diseases (atopic dermatitis, psoriasis) the expression of TLR2, TLR4 and TLR9 was low compared to normal skin. In parapsoriasis the expression of the three TLRs was similar to control. By contrast, in MF skin we observed a strong intensity of labelling with the three TLRs in the epidermis. Concerning SS, the expression of TLR2, TLR4 and TLR9 was intermediate between inflammatory lesions and MF. Thus, the development of skin lesions in MF appears associated with an increase of TLR2, TLR4 and TLR9 expression by keratinocytes in cutaneous lesions, which could play a role in the chronic activation of T lymphocytes in the skin.