The identity of inflammatory immune cells that activate pathogenic autoreactive cells in the brain, and may be important in multiple sclerosis (MS) progression, is reported this week in Nature Immunology.
Multiple sclerosis (MS) is an autoimmune disease in which immune cells attack the protective sheathing of nerve fibers and cause axonal damage. Both CD4+ helper cells and CD8+ “killer” T cell subsets contribute to the disease process, but how naive CD8+ cells become activated or “armed” in brain tissues remained mysterious.
Using a mouse model of MS in which damage is initiated by CD4+ T cells, Joan Goverman and colleagues identified a type of antigen-presenting cells, called Tip-DCs, that infiltrate the brain tissue and engulf damaged cells and debris. Tip-DCs can present small bits of protein derived from this neuronal cell damage to CD8+ T cells that have been recruited to brain lesions, enlisting new killer cells and potentiating the damage process.
The authors suggest that a similar scenario may exist in MS patients whereby recruitment and activation of CD8+ killer cells contributes to ongoing axonal destruction.