Macrophage differentiation marker MyD88 is a member of the Toll/IL-1 receptor family.

The interleukin-1 receptor in mammals and the product of the Toll gene in Drosophila are related transmembrane receptors, involved in the activation of transcription factors of the rel family. Whereas the interleukin-1 receptor mediates the effects of interleukin-1 in the immune system, Toll is part of the system that determines dorsoventral polarity in the Drosophila embryo, although Toll may also have a function in the immune response in the fly. Here, I demonstrate that the open reading frame of MyD88, a gene induced in myeloid differentiation, is related to the cytoplasmic domains of the interleukin-1 receptor and the Toll gene product. The three related proteins define a family of signal transmitters, the original function of which may be to mediate responses in the immune system.