T cells are poised to invade the CNS through a distinct transcriptional cytotoxic program in MS

Abstract

Oral Presentations 28 (3S) 63 journals.sagepub.com/home/msj Multiple Sclerosis Journal 2022; 28: (3S) 3-129 to 59,7% of the results on the gait test can be explained with all the variables included. Of the included variables included the time spent in the final part of stance phase shows the greatest amount of association, which alone explains 57,3% of the results. Conclusion: Push-off appears highly relevant for the ability to walk long distances on a gait test. The use of wearable technology sensors offers the clinician a tool to assess and evaluate changes related to gait. This can be used in clinical practice without any negative impacts on established routines. Multiple sclerosis (MS) is the prototypical idiopathic neuroin-flammatory disorder. MS affects young adults and children, and is clinically characterized by bouts of focal inflammatory activity in the brain and spinal cord, leading to unpredictable and temporary clinical episodes of dysfunction, such as optic neuritis (causing vision loss) or transverse myelitis (leading to numbness and or limb paralysis). Experimental allergic encephalomyelitis, when induced in mice, remains a good, although very imperfect, model of MS. In both MS and EAE, the disease evolves as a relapsing remitting disease, followed by irreversible progression of handicap. Pathological analyses of human brains of patients affected by MS, and of CNS from animals affected by EAE, provided insight on the immunopathol-ogy of these diseases. We now know that these CNS-targeted disorders involves CD4 and CD8 lymphocytes, monocytes-macrophages-dendritic cells, microglia and astrocytes which have different and sometimes divergent or opposing effects on the various phases of the disease. We also know that oligoden-drocytes and neurons are the main target of the immune attack, and that endothelial cells also contribute to the recruitment of immune cells into the CNS. Using recent technological advances in Flow cytometry, scR-NAseq, cell biology, microscopy and system biology allowed the field to provide a thorough characterization of the role of each cell type in neuroinflammation, both in human MS and in EAE, including molecules involved in trans-endothelial migration (CAMs, chemokines and chemokine receptors). The lecture will present some novel data on this topic, focusing on endothelial molecules involved in diapedesis of immune cells across vascular brain structures. Disclosure Nothing to disclose O079 T cells are poised to invade the CNS through a distinct transcriptional cytotoxic program in MS Introduction: In MS patients, pathogenic CD4 + T cells cross the blood-brain barrier, also allowing other immune populations, including CD8 + T cells, to infiltrate the brain. How transcription factors known to control the cytotoxic T-cell program are involved in this process is underexplored. Objectives: To assess whether changes in the cytotoxic T-cell program explain the propensity of CD4 + and CD8 + subsets to enter the MS brain. Aims: By delineating which intrinsic factors underlie brain hom-ing of human T cells, we aim to better understand the cause of MS. Methods: Expression patterns of RUNX3, EOMES and T-bet as key determinants of the T-cell effector program were examined and associated with cytotoxic and brain-homing features of path-ogenic CD4 + (Th17.1) and CD8 + (CD20 dim) T cells by FACS. We used blood and CSF samples as well as brain tissues from different MS cohorts. The brain-homing capacity was verified by studying blood of natalizumab-treated MS patients and by performing in vitro BBB transmigration assays. Results: Within both CD4 + and CD8 + T cells, the frequency of RUNX3-expressing memory populations with cytotoxic potential (CD107a +) was reduced in the blood of 18 treatment-naïve early MS patients versus 8 matched healthy controls (p<0.001 and p<0.01, respectively). This decline was restored after natal-izumab treatment (n=8). Similar results were obtained for EOMES, which was mainly expressed by CD8 + T cells. In RUNX3-expressing cells, we found an additional loss in T-bet, which corresponded to the presence of MS risk SNP rs6672420 (RUNX3). In contrast to RUNX3 + EOMES-T-bet + (granzyme B +) cells, RUNX3 + EOMES + T-bet-cells displayed high levels of CCR5 and granzyme K, which were enriched in CD20 dim and CD69 + subsets. This was most prominent in MS CSF, where Th17.1 cells predominated the memory T-cell compartment compared to paired blood (n=15) and control CSF (n=8). Of all CD4 + T-cell subsets analyzed, Th17.1 had the highest proportion of RUNX3 + EOMES + T-bet-cells and produced granzyme K, especially after crossing the BBB in vitro. In post-mortem MS brain tissue (n=8), T-bet was reexpressed and EOMES was downregu-lated in predominating CD20 dim (CD69 +) CD8 + T cells, which was accompanied by granzyme B and K coproduction. Conclusions: This work reveals that in MS patients, coexpres-sion of RUNX3 and EOMES, but not T-bet, defines CD4 + and