TLR4 and allergic disease: Similarity between the HDM allergen Der p 2 and myeloid differentiation protein‐2 (MD‐2, lymphocyte antigen 96), a co‐receptor protein for LPS responses, has been assumed to implicate LPS and Der p 2 as key determinants of why TLR4 activation is essential for the development of allergy to HDM, and this is consistent with the ability of LPS to drive allergic immunity under certain conditions 32, 33.