T cells are considered pivotal in the pathology of multiple sclerosis (MS), but their function and antigen specificity are unknown. To unravel the role of T cells in MS pathology, we performed a comprehensive analysis on T cells recovered from paired blood, cerebrospinal fluid (CSF), normal-appearing white matter (NAWM) and white matter lesions (WM L) from 27 MS patients with advanced disease shortly after death. The differentiation status of T cells in these compartments was determined by ex vivo flow cytometry and immunohistochemistry.
T-cell reactivity in short-term T-cell lines (TCL), generated by non-specific stimulation of T cells recovered from the same compartments, was determined by intracellular cytokine flow cytometry. Central memory T cells predominated in CSF and effector memory T cells were enriched in NAWM and WM Lesion. WM Lesion-derived CD8+ T cells represent chronically activated T cells expressing a cytotoxic effector phenotype (CD95L and granzyme B) indicative for local antigenic stimulation (CD137). The same lesions also contained higher CD8+ T-cell frequencies expressing co-inhibitory (TIM3 and PD1) and co-stimulatory (ICOS) T-cell receptors, yet no evidence for T-cell senescence (CD57) was observed.
The oligoclonal T-cell receptor (TCR) repertoire, particularly among CD8+ T cells, correlated between TCL generated from anatomically separated WM Lesions of the same MS patient, but not between paired NAWM and WM Lesion. Whereas no substantial T-cell reactivity was detected towards seven candidate human MS-associated autoantigens (cMSAg), brisk CD8+ T-cell reactivity was detected in multiple WM Lesions-derived TCL towards autologous Epstein-Barr virus (EBV) infected B cells (autoBLCL).
Collectively, the data suggest the involvement of effector memory cytotoxic T cells recognizing antigens expressed by autoBLCL, but not the assayed human cMSAg, in WML of MS patients.
However do we find T cell reactivity to EBV because we are looking for reactivity to EBV