While the negative relationship between polymorphisms in TRIM5 and TRIM22 and the risk of developing MS could conceivably be related to altered immune responses in response to HERV transcription or even reduced HERV transcription, the positive relationship between MS risk and the polymorphism rs391745 upstream of the HERV-Fc1 locus on the X chromosome [40, 85, 86] could also be connected to altered HERV expression, as we will now consider. Here, TRIM5 is linked to myeloid sarcoma.