This protein was identified as a likely PRR by Medzhitov, Janeway and colleagues in 1997, as they found human TLR4 (first known as hToll) to be homologous to the Drosophila melanogaster Toll protein [21], which had been previously identified as a sensor of fungal infections by Lemaitre et al. [22]. Here, TLR4 is linked to fungal infectious disease.