Myelin-specific CD8 T cells require IFNγ responsiveness to optimally suppress CNS autoimmunity

Abstract

Abstract Investigating the complex cellular interplay controlling immunopathogenic and immunoregulatory responses is critical for understanding multiple sclerosis (MS) and for developing successful immunotherapies. Our group has demonstrated that central nervous system (CNS) myelin-specific CD8 T cells unexpectedly harbor striking regulatory capacity in both mouse and human. In particular, PLP178–191-specific CD8 T cells (PLP-CD8) robustly suppress the MS mouse model experimental autoimmune encephalomyelitis (EAE). We have recently shown this depends on PLP-CD8 elaborating IFNγ and perforin in a coordinated suppression program over time. However, the cellular target and downstream effects of CD8 T cell-elaborated IFNγ remains poorly understood. Here, we show that while WT PLP-CD8 were robustly suppressive in IFNγR-deficient mice, IFNγR-deficient PLP-CD8 exhibited defective suppression in WT mice. Further, compared to WT counterparts, IFNγR-deficient PLP-CD8 were defective in suppressing disease in IFNγ-deficient recipients, a scenario in which the only IFNγ WT PLP-CD8 “see” is their own. These data indicate that myelin-specific CD8 T cells must sense their own IFNγ in an autocrine/paracrine manner to optimally perform autoregulatory function in vivo. Further mechanistic dissection showed that IFNγR-deficient PLP-CD8 exhibited altered degranulation/granzyme profiles, altered migration in recipients, and potential deficits in killing capacity. Collectively, this work suggests that myelin-specific CD8 T cells require IFNγ-responsiveness to optimally regulate CNS autoimmunity and may help elucidate future adoptive immunotherapeutic approaches in MS.