Characterization of natural killer cells in paired CSF and blood samples during neuroinflammation

Natural killer (NK) cells from paired CSF and blood samples of patients with multiple sclerosis (MS), other neuroinflammatory diseases (IND), and non-inflammatory neurological diseases (NIND) were characterized using flow cytometry. NK cell frequency in CSF was overall decreased compared to blood, particularly in MS patients. In contrast to blood NK cells, during neuroinflammation, CSF NK cells display an immature phenotype with bright expression of CD56 and CD27 and reduced CX3CR1 expression. Our findings suggest that, as for central memory T cells, CSF may represent an intermediary compartment for NK cell trafficking and differentiation before entering the CNS parenchyma.