AbstractThe role of Toll-like receptor-2 (TLR2) in radio-resistance remained largely unknown. TLR2 knockout (TLR2−/−) mice received radiation of 6.5 Gy and then were studied. We found that radiation resulted in more severe mortality and morbidity rates in TLR2−/−mice. The cause of death in TLR2−/−mice may be severe and persistent bone marrow cell loss. Injection of the TLR2 agonist Pam3CSK4into wild type (WT) mice induced radio-resistance. Myd88−/−mice were more susceptible to radiation. In conclusion, our data indicate that, similar to TLR4, TLR2 plays a critical role in radio-resistance.