Illness may be caused by constitutive activation of human TLR7 or TLR8 in the bacterial artificial chromosome positive mice as increased TLR7 and TLR8 expression or activation has previously been implicated in autoimmune disease.
The presence of the TLR7rs179008/Gln11Leu polymorphism in sarcoidosis may determine an alteration of TLR7 function hampering the signaling pathway involved in the onset of both cellular and humoral autoimmunity.
Genetic abnormalities in some receptors like TLR2, TLR3 and TLR4 have been associated with susceptibility to fungal and viral infections while other aberrations in TLR genes such as TLR3, TLR7 and TLR9 may predispose to autoimmunity.
Because inappropriate expression of TLR7 has been implicated in the development of systemic autoimmunity, these findings may also be relevant for the understanding of autoimmunity.
Both TLR8 and TLR7 are functional candidate genes owing to their key roles as pathogen recognition receptors and, in the case of TLR7, overexpression has been associated directly with murine autoimmune disease.
In this review, we discuss the rationale for self-recognition by TLR7 and TLR9 as an important part of the development of lupus and other autoimmune diseases.
Interestingly, Toll-like receptor 4 (TLR4) is the cognate receptor for LPS and its activation can induces up-regulation of other TLRs, such as TLR7 (the receptor for TMEV) and 9, known to be involved in autoimmunity.