TLR2 expression in medicinal leech

It is well known that Toll-like receptors (TLRs) play a central role for innate immunity in both vertebrates and many invertebrates, by recognizing conserved pathogen-associated molecular patterns in order to trigger the innate immune response. In the case of Gram-positive bacteria, TLR2 is the primary receptor to detect them and mainly senses lipoteichoic acid LTA (a predominant surface glycolipid of Gram+). In order to evaluate whether the recognition of Gram+ bacteria involves TLR2 in leech as well, we performed immunofluorescent and Western blot analysis on leech body wall LTA injected. Our morphological and histochemical results clearly indicate that LTA induces immune cells migrating toward the stimulated area. The expression profile of TLR2 has been also evaluated by Western blot analysis highlighting the presence of an immunoreactive product at about 100 kDa, in according with that found in vertebrates. Moreover, to characterize the migrating immune cells, we further performed immunofluorescent experiments using antibodies against the AIF-1 (Allograft Inflammatory Factor-1) and RNASET2 (a member of the ribonuclease T2 family) factors. As we previously demonstrated, the expression of these two markers is enhanced after Gram- bacterial lipopolysaccharides (LPS) infection and is mainly located in activated macrophages. Our results clearly show that after LTA injection, numerous AIF-1+/RNASET2+ macrophages migrate towards the infected area and express TLR2. Given these encouraging preliminary results, indicating that TLR2 may functions as LTA receptor in leeches as well, our further research will be focused to better clarify TLR2 expression and signaling in the medicinal leech.