Fig. 1

CD45RA⁺CD27⁻CCR7⁻CD127⁻ CD8⁺ T_EMRA cells in human diseases. A In human autoimmune diseases such as multiple sclerosis and during viral infection as such COVID-19, CD45RA⁺CD27⁻CCR7⁻CD127⁻ KIR⁺CD8⁺ T cells are increased in the peripheral blood and inflamed tissues of patients. KIR⁺CD8⁺ T cells kill T-cell receptor activated pathogenic and autoreactive CD4⁺ T cells to prevent the development of autoimmune diseases and dampen autoimmune immune responses. B CD45RA⁺CD27⁻CCR7⁻CD127⁻ CD8⁺ T_EMRA cells are clonally expanded in the cerebrospinal fluid from patients with neurodegenerative diseases such as multiple sclerosis (an autoimmune disease) and Alzheimer’s disease. The function and specific cell-type classification of these CD8⁺ T_EMRA cells are unknown. It is yet to be determined if they act like cytotoxic T lymphocytes to damage the center nervous system, or regulatory T cells to subdue rogue immune responses. Created with BioRender (Biorender.com)