MECHANISM OF GAMMA-DELTA T-CELL-INDUCED HUMAN OLIGODENDROCYTE CYTOTOXICITY - RELEVANCE TO MULTIPLE-SCLEROSIS

gamma delta T cells may contribute to the pathogenesis of Multiple Scl erosis (MS) via cytotoxicity directed at the myelin-oligodendrocyte un it. We have previously demonstrated that peripheral blood-derived gamm a delta T cells lyse fresh human oligodendrocytes in vitro. The presen t work extends these observations to gamma delta T cells derived from both peripheral blood (PBL) and cerebrospinal fluid (CSF) of MS and no n-MS neurological disease controls and addresses the mechanism of cell ular cytotoxicity. We found that MS patients contained increased propo rtions of V delta 1(+) gamma delta T cells in both CSF and PBL samples compared to other neurological disease (OND) controls. Although gamma delta T cells from all patients were cytotoxic towards Daudi, RPMI 82 26, U937, Jurkat, oligodendroglioma and fresh human oligodendrocyte ta rgets, OND-derived, V delta 2(+) rich, populations derived from the CS F exhibited greater cytotoxicity towards cell lines (Daudi, RPMI 8226) known to express high levels of heat shock proteins (hsp). To clarify the mechanism(s) of cytotoxicity used by gamma delta T cells, we firs t showed that cell-target contact was necessary by the use of physical barriers (transwells), which reduced target cell lysis by at least 75 %. The use of Ca2+-free media reduced lysis by up to 50%, but fully bl ocking gamma delta T cell Perforin release and function by either Ca2 chelation (Mg,EGTA) or the H+-ATPase inhibitor Concanamycin-A (CMA), completely abrogated the lysis of Fas(-)/hsp60(high) expressing target s (Daudi, U937). However, additional treatment with Brefeldin A was re quired for the complete inhibition of gamma delta T cell mediated kill ing of Fas(+) expressing Jurkat targets and fresh human brain-derived oligodendrocytes. Inhibition of granzyme activity by an isocoumarin co mpound reduced cytolysis only slightly. The use of either Brefeldin A or an anti-Fas antibody alone did not significantly affect lysis. Thes e findings suggest that in MS, gamma delta T cells may utilize either the Fas-mediated or Perforin-based cell cytotoxicity pathways in exert ing oligodendrocyte damage, though the Perforin pathway is predominant . (C) 1998 Elsevier Science B.V. All rights reserved.