Prognostic value of NK cell/ T cell ratios for disease activity in multiple sclerosis

BACKGROUND: Natural killer (NK) cells may play a role in multiple sclerosis (MS). Ratios of NK cells/CD4+ T cells have been proposed as a biomarker for the therapeutic effect of stem-cell transplantation in MS.

OBJECTIVES: To explore the relevance of this ratio in MS patients by analysing NK and T cell subsets, as well as their prognostic value for disease activity.

METHODS: Baseline peripheral blood mononuclear cells of 50 relapsing-remitting MS patients, participating in our vitamin D supplementation study (SOLARIUM), were analysed with flow cytometry. Disease activity was measured as new MRI-lesions, relapses, and mean plasma neurofilament light chain (NfL) levels after 48 weeks of follow-up.

RESULTS: The proportion of NK cells correlated negatively with CD4+ T cells [R=-0.335 p=0.001] and IL17-A+ CD4+ T cells [R=-0.203 p=0.043]. Participants with MRI activity or relapses displayed lower NK/IL-17A+ CD4+ T cell ratios [p=0.025 and p=0.006, respectively]. The NK/IL-17A+ CD4+ T cell ratio correlated negatively with NfL levels [R=-0.320 p=0.050]. Vitamin D supplementation did not affect these ratios.

CONCLUSIONS: Our data suggests a protective role of an expanded NK cell compartment compared to the CD4+ T cell subset fractions in RRMS patients. NK/CD4+ T cell ratios may be a prognostic biomarker for disease activity in MS.