Brown, G.J.Cañete, P.F.Wang, H.Medhavy, A.Bones, J.Roco, J.A.He, Y.Qin, Y.Cappello, J.Ellyard, J.I.Bassett, K.Shen, Q.Burgio, G.Zhang, Y.Turnbull, C.Meng, X.Wu, P.Cho, E.Miosge, L.A.Andrews, T.D.et al.2022-06-162022-06-162022Nature, 2022; 605(7909):349-3560028-08361476-4687https://hdl.handle.net/2440/135460Although circumstantial evidence supports enhanced Toll-like receptor 7 (TLR7) signalling as a mechanism of human systemic autoimmune disease1-7, evidence of lupus-causing TLR7 gene variants is lacking. Here we describe human systemic lupus erythematosus caused by a TLR7 gain-of-function variant. TLR7 is a sensor of viral RNA8,9 and binds to guanosine10-12. We identified a de novo, previously undescribed missense TLR7Y264H variant in a child with severe lupus and additional variants in other patients with lupus. The TLR7Y264H variant selectively increased sensing of guanosine and 2',3'-cGMP10-12, and was sufficient to cause lupus when introduced into mice. We show that enhanced TLR7 signalling drives aberrant survival of B cell receptor (BCR)-activated B cells, and in a cell-intrinsic manner, accumulation of CD11c+ age-associated B cells and germinal centre B cells. Follicular and extrafollicular helper T cells were also increased but these phenotypes were cell-extrinsic. Deficiency of MyD88 (an adaptor protein downstream of TLR7) rescued autoimmunity, aberrant B cell survival, and all cellular and serological phenotypes. Despite prominent spontaneous germinal-centre formation in Tlr7Y264H mice, autoimmunity was not ameliorated by germinal-centre deficiency, suggesting an extrafollicular origin of pathogenic B cells. We establish the importance of TLR7 and guanosine-containing self-ligands for human lupus pathogenesis, which paves the way for therapeutic TLR7 or MyD88 inhibition.en© The Author(s) 2022 Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/.B-LymphocytesAnimalsHumansMiceLupus Erythematosus, SystemicGuanosineCyclic GMPAutoimmunityToll-Like Receptor 7Myeloid Differentiation Factor 88Gain of Function MutationB-LymphocytesAnimalsHumansMiceLupus Erythematosus, SystemicGuanosineCyclic GMPAutoimmunityToll-Like Receptor 7Myeloid Differentiation Factor 88Gain of Function MutationJournal article10.1038/s41586-022-04642-z2022-06-16611099Lopez, A.F. [0000-0001-7430-0135]