TLR7 and Autoimmunity: Incidentally, the X chromosome has a high density of genes involved in immune functions (11, 12), and some of these, including TLR7, TASL, CXCR3, or CD40LG, tend to be overexpressed in autoimmune conditions, suggesting a causal link between autoimmunity and X-linked gene regulation (2, 5, 13).