Figure 4.

Induction of oligodendrocyte death by CD137L-activated microglia. (A) Expression of CD137L on the oligodendrocyte cell line OLN93 was determined by flow cytometry. Open histogram: Isotype control. Grey histogram: Anti-CD137L monoclonal antibody (clone TKS-1). (B) N9 and OLN93 cells were cultured for 24 h at a 1:1 ratio (1.5×10⁵ each) on plates that had been coated with nothing (PBS) or 10 μg/mL of Fc control protein or 10 μg/mL of CD137-Fc protein. (C) The rates of OLN93 cell apoptosis in co-cultures with primary microglia from WT or CD137L^-/- mice was determined 48 h after initiation of CD137L signaling by 7-AAD and Annexin V staining. Numbers in quadrants indicate percentages of cells. These experiments were repeated two to three times with similar results. * P <0.05; ** P <0.01.