Localizing central nervous system immune surveillance: meningeal antigen-presenting cells activate T cells during experimental autoimmune encephalomyelitis.
OBJECTIVE
The onset of neurological signs in experimental autoimmune encephalomyelitis is tightly associated with infiltration and reactivation of T cells in the central nervous system. The anatomic localization of the initial T cell-antigen-presenting cell (APC) interactions leading to reactivation of T cells in the central nervous system is, however, still unclear. We hypothesized that activated CD4(+) T cells gain direct access to the subarachnoid space and become reactivated on encounter with cognate antigen in this compartment.


METHODS
C57Bl/6 mice were immunized with MOG35-55, and interactions between CD4(+) T cells and major histocompatibility class II+ APCs in the subarachnoid space were investigated using flow cytometry, confocal microscopy of leptomeningeal whole-mount preparations, time-lapse microscopy of leptomeningeal explants, and in vitro proliferation assays.


RESULTS
CD4(+) T cells, polarized to produce Th1/Th17 cytokines, accumulated in the subarachnoid space early during the course of experimental autoimmune encephalomyelitis, before CD4(+) T cells were detected in the spinal cord parenchyma. At this time point, leptomeningeal but not parenchymal CD4(+) T cells incorporated bromodeoxyuridine, indicating local proliferation of CD4(+) T cells in the subarachnoid space. Time-lapse microscopy indicated that these CD4(+) T cells actively scanned the tissue and interacted with local major histocompatibility class II+ APCs, resulting in long-lasting interactions between CD4(+) T cells and major histocompatibility class II+ APCs, suggestive of immunological synapses.


CONCLUSIONS
These results support the concept that immune surveillance of the central nervous system involves the subarachnoid space and indicate that the leptomeninges play an important role in experimental autoimmune encephalomyelitis initiation.
Kivisäkk
Pia
P
Center for Neurological Diseases, Brigham and Women's Hospital, Department of Neurology, Harvard Medical School, Boston, MA 02115, USA.
Imitola
Jaime
J
Rasmussen
Stine
S
Elyaman
Wassim
W
Zhu
Bing
B
Ransohoff
Richard M
RM
Khoury
Samia J
SJ
D000818:Animals; D000938:Antigen-Presenting Cells / Q000276:immunology*; D015703:Antigens, CD / Q000378:metabolism; D001973:Bromodeoxyuridine / Q000378:metabolism; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology; D002465:Cell Movement / Q000276:immunology; D049109:Cell Proliferation; D002490:Central Nervous System / Q000276:immunology*; D016207:Cytokines / Q000378:metabolism; D004195:Disease Models, Animal; D004681:Encephalomyelitis, Autoimmune, Experimental / Q000139:chemically induced / Q000276:immunology* / Q000473:pathology; D005434:Flow Cytometry; D006023:Glycoproteins; D015395:Histocompatibility Antigens Class I / Q000276:immunology; D007157:Immunologic Surveillance / Q000276:immunology*; D008578:Meninges / Q000276:immunology* / Q000473:pathology; D051379:Mice; D008810:Mice, Inbred C57BL; D018613:Microscopy, Confocal / Q000379:methods; D063308:Myelin-Oligodendrocyte Glycoprotein; D010446:Peptide Fragments; D013116:Spinal Cord / Q000473:pathology; D013346:Subarachnoid Space / Q000166:cytology / Q000276:immunology; D013997:Time Factors
D015703:Antigens, CD; D016207:Cytokines; D006023:Glycoproteins; D015395:Histocompatibility Antigens Class I; D063308:Myelin-Oligodendrocyte Glycoprotein; D010446:Peptide Fragments; C445081:myelin oligodendrocyte glycoprotein (35-55); D001973:Bromodeoxyuridine