Another potentially important aspect of the TLR pathways is that the TLR7 and TLR8 genes are located on the X-chromosome: there are indications that TLR7 may escape the normal silencing of one of the two X chromosomes in females (67), resulting in higher levels of TLR7 expression and, hence, stronger responses to TLR7 simulation in immune cells in women, perhaps contributing to the 9:1 gender bias in SLE. Here, TLR7 is linked to systemic lupus erythematosus.