CD3-T cell receptor co-stimulation through SLAMF3 and SLAMF6 receptors enhances RORγt recruitment to the IL17A promoter in human T lymphocytes.

Th17 lymphocytes play a key role during immune responses against bacteria and fungi and are involved in the pathophysiology of multiple autoimmune disorders. The co-stimulatory molecules SLAMF3 and SLAMF6 have been implicated in the formation of Th17 phenotypes and IL-17A expression. Increased surface expression of SLAMF3 and SLAMF6 has been linked with disease activity in systemic lupus erythematosus. Here we demonstrate that in human total T lymphocytes the canonical CD28 and the non-canonical SLAMF3/SLAMF6 co-stimulatory pathways cooperate in the recruitment of the transcription factor NFAT1 to the IL17A promoter. Furthermore, the dominance of the SLAMF3/SLAMF6 pathway in inducing IL-17A production can be attributed to an increased nuclear abundance and recruitment of RORγt to the IL17A promoter. Thus, we have identified an additional mechanism that may be central for the specific control of IL17A gene regulation in systemic lupus erythematosus T lymphocytes.