Recent studies indicate that several
Toll-like receptors (TLRs) are implicated in recognizing viral structures and instigating immune responses against
viral infections. The aim of this study is to examine the expression of TLRs and proinflammatory
cytokines in
viral skin diseases such as
verruca vulgaris (VV) and
molluscum contagiosum (MC). Reverse transcription-polymerase chain reaction and immunostaining of skin samples were performed to determine the expression of specific
antiviral and proinflammatory
cytokines as well as 5 TLRs (TLR2, 3, 4, 7, and 9). In normal human skin, TLR2, 4, and 7
mRNA was constitutively expressed, whereas little TLR3 and 9
mRNA was detected. Compared to normal skin (NS), TLR3 and 9
mRNA was clearly expressed in VV and MC specimens. Likewise, immunohistochemistry indicated that keratinocytes in NS constitutively expressed TLR2, 4, and 7; however, TLR3 was rarely detected and TLR9 was only weakly expressed, whereas 5 TLRs were all strongly expressed on the epidermal keratinocytes of VV and MC lesions. In addition, the
mRNA expression of IFN-beta and
TNF-alpha was upregulated in the VV and MC samples. Immunohistochemistry indicated that IFN-beta and
TNF-alpha were predominantly localized in the granular layer in the VV lesions and adjacent to the MC bodies. Our results indicated that VV and MC skin lesions expressed TLR3 and 9 in addition to IFN-beta and
TNF-alpha. These viral-induced proinflammatory
cytokines may play a pivotal role in cutaneous innate immune responses.