CD27 and Huntington disease: To test the Fas sensitivity of memory B-cells relative to naïve B-cells, purified CD27+ and CD27− B-cells from CIR and HD subjects were co-cultured with a Fas-agonizing antibody (CH11, 2 μg/ml) or rhTRAIL (1 μg/ml) for 18 hours after which apoptosis was assessed by Annexin-V/propidium iodide staining.