Several studies have linked human endogenous retroviruses (HERVs) with autoimmune disease. We have previously demonstrated that the full-length polymorphic HERV-K113 provirus prevalence is increased in both Sjögren's syndrome (15.6%) and multiple sclerosis (11.9%) compared with the normal UK population (4%). Recent studies have shown that exogenous viral RNA can activate dendritic cells via the TLR7/8-mediated pathway. In this study we investigate the possibility that HERV-K113 RNA sequences are capable of activating both dendritic cells and macrophages. We examine the production of cytokines by both cell types in response to a series of different HERV-K113 RNA species to identify any differences in the profile produced.