Mapping Toll-Like Receptor Activity in Different Stages of Cutaneous T-Cell Lymphoma

It is known that human keratinocytes (KCs) express Toll-like receptors (TLRs). However, published reports conflict regarding TLR expression in cutaneous T-cell lymphoma patient's KCs. To define the pattern of expression and detect any differences of TLRs 1-9 and p65 expression in epidermal KCs, tumor infiltrate, and endothelial cell types using immunohistochemical stains on fixed and paraffin-embedded sections of mycosis fungoides (MF) in patch, plaque, and nodular stages. MF cases showed no change in pattern of TLRs expressed through different stages but increased epidermal staining of TLRs 2, 3, 4, 5, 6, and 8 with higher scores associated with more aggressive stages. Endothelial cell staining was increased for TLR 4 and 6. Tumor infiltrate staining was strongest with TLRs 5 and 7. Individual cases with disease progression showed increased intensity of TLRs 4, 5, and 6 staining in the epidermis, tumor infiltrate, and endothelial cell. p65 verified nuclear factor kappa B activation of the TLR pathway with trace staining of the epidermis and 1-2+ staining of tumor infiltrate. MF cases showed increased epidermal expression of TLRs and increased endothelial cell staining compared with controls. TLR expression may be driven by antigenic stimulation and may play a role in the activation of neoplastic T cells in the skin. Further definition of TLR patterns may refine the use of TLR modifiers for treatment.