Cells were harvested and proliferation and secreted cytokines analysed as described see more previously. Proteins were immobilized on the beads, as per the manufacturer’s instructions. Briefly, 0·5 ml of the provided Dynabeads were washed twice with phosphate-buffered saline (PBS), resuspended in 200 µl of PBS per tube, and 20 µg of anti-CD3ε and/or the indicated µg amount of anti-BTLA test antibody (or antibodies) reagent was absorbed passively to the beads, mixed well and incubated at room temperature for 60 min. The tube was vortexed (bench top) every 3 min to ensure
mixing. Then 100 µl of a 0·5% bovine serum albumin (BSA) solution in PBS was added to each tube and the volume adjusted to 500 µl with PBS to block any unoccupied bead surface. The beads were incubated at 4°C for
3 days with shaking and then washed three times with 0·1% BSA in PBS buffer. They were finally resuspended in 500 µl of 0·1% BSA in PBS to yield a final bead concentration of 4 × 108/ml and the final bead : cell ratio in the well was adjusted to 1:1. For the mixed lymphocyte reaction (MLR) in vitro assay, T cells Proteasome inhibitor were isolated from the spleens of C57BL/6 mice with a pan T cell-negative selection isolation kit (Miltenyi Biotech); antigen-presenting cells (APC) were selected negatively from the spleens of BALB/c mice (Miltenyi Biotech). The APC were incubated with mitomycin C (Sigma) at 25 µg/ml for 30 min at 37°C and then washed three times. T cells were cultured with mitomycin C-treated APC at a 1:1 ratio, with 2 × 105 cells per well in 200 µl volume for 5 days. For the last 16 h, 1 µCi of [3H]-thymidine (MP Biomedicals, Inc., Irvine, CA, USA) was added to each well. The cells were then harvested and [3H]-incorporation measured using a 1450 Microbeta Liquid Scintillation and Luminescence Counter Nutlin-3 manufacturer (Perkin Elmer, Sherton, CT, USA). For the ovalbumin (OVA) antigen-specific T cell proliferation in vitro assay, CD4 T cells were isolated from the spleens of DO11.10 mice by CD4 T cell-negative selection (Miltenyi Biotec) and APCs were isolated from same mice with an AutoMACS T cell depletion
kit (Miltenyi Biotec). The APCs were incubated with mitomycin C at 25 µg/ml for 30 min at 37°C and then washed three times. The T cells were stimulated by 0·1 µg/ml OVA peptide in the presence of mitomycin C-treated APC at a 1:1 ratio, with 2 × 105 cells per well in a 200 µl volume. Cell proliferation was measured at day 3 as described above. Mouse B cells were purified from C57BL/6 mouse splenocytes by AutoMACS-negative selection (Miltenyi Biotec) and 100 000 cells were incubated in duplicate in 96-well flat-bottomed plates in RPMI-1640 (Invitrogen, Inc.) with 10% heat-inactivated fetal bovine serum (FBS) (54°C for 45 min), 1 mM HEPES and 55 µM β-mercaptoethanol (all from Gibco). Cells were stimulated with 2 µg/ml of lipopolysaccaride (List Biological Laboratories, Inc.