Studies have shown that the function of this gene is related to the formation of the dorsal–ventral axis during the embryonic development of Drosophila.16 In 1988, Hashimoto et al. discovered that the Toll gene encodes a transmembrane protein and clarified the structure of the Toll protein.17 In 1991, Gay et al. found that Toll protein had structural homology with interleukin-1 (IL-1), a natural immune molecule in mammals, suggesting that the function of Toll may be related to immunity.18 In 1996, Hoffmann team found that Toll plays a role in the resistance of Drosophila to fungal infection. This evidence concerns the gene TLR4 and fungal infectious disease.