GRN and Autoimmunity: The TNFα‐inhibiting effect of PGRN was blocked by the administration of anti‐PGRN‐Fab.2 The occurrence of PGRN‐Abs is associated to an active disease state.1 As an underlying cause for autoimmunity to progranulin, we found the inactivated (pThr320) protein phosphatase 1 inducing an immunogenic hyperphosphorylation of progranulin at Ser81 to be the underlying cause of PGRN‐Abs.