It has been observed that TLR7 encoded on the X chromosome is biallelically expressed in the pDCs, B cells and monocytes not only of women (XX) but also of men with Klinefelter’s syndrome (XXY), and that immune cells with biallelic TLR7 expression show greater transcriptional activity compared to monoallellic cells [106]. The gene discussed is TLR7; the disease is Klinefelter syndrome.