Neuroinflammation in the brain and spinal cord, a process driven largely by CNS-resident microglia, has been proposed as a significant contributor to disability accumulation in patients with multiple sclerosis (MS). BTK is expressed in microglia, as well as B lymphocytes and monocytes/macrophages found in the periphery. Previous immunohistochemistry studies and single-nucleus RNA sequencing (snRNAseq) from tissues derived from autopsy samples demonstrated that BTK was expressed in B cells and in microglial cells, with increased levels in MS lesion samples. BTK inhibition may provide therapeutic benefit within the CNS by targeting innate immunity associated with MS disease progression.

Immunofluorescence staining and RNAseq in human tri-culture cells. Cytokine secretion assays were performed using enzyme-linked immunosorbent assay (ELISA).

We extend our previous findings on the role of BTK in microglia to show that BTK-dependent inflammatory signalling in human microglia and tri-cultures can be modulated using tolebrutinib in vitro. Our work contributes to improved understanding of BTK signalling in neuroinflammation and how BTK inhibitors could target the neuroinflammation thought to contribute to MS disability progression.