Münster. Although the CNS is immune privileged, continuous search for pathogens and tumours by immune cells within the CNS is indispensable. Thus, distinct immune-cell populations also cross the blood–brain barrier independently of inflammation/under homeostatic conditions. It was previously shown that effector memory T cells populate healthy CNS parenchyma in humans and, independently, that CCR5-expressing lymphocytes as well as CCR5 ligands are enriched in the CNS of patients with multiple sclerosis. Apart from the recently described CD8+ CNS tissue-resident memory T cells, CRC researchers from Muenster identified a population of CD4+CCR5high effector memory cells as brain parenchyma-surveilling cells. In an interview with the German radio news channel NDR info they explain these latest insights. Listen to the radio report (in German):

Adapted from: Herich S, Schneider-Hohendorf T, Rohlmann A, Khaleghi Ghadiri M, Schulte-Mecklenbeck A, Zondler L, Janoschka C, Ostkamp P, Richter J, Breuer J, Dimitrov S, Rammensee HG, Grauer OM, Klotz L, Gross CC, Stummer W, Missler M, Zarbock A, Vestweber D, Wiendl H, Schwab N. Human CCR5high effector memory cells perform CNS parenchymal immune surveillance via GZMK-mediated transendothelial diapedesis. Brain.142(11):3411-3427.