Flow Cytometry for Anti-Neurexin-1-beta [IPI-NRXN1b.35]

EC₅₀: A fourteen point titration of antibody concentrations, ranging from 660 nM (0.1 mg/mL) to 4.42 pM with a 1:2.5 dilution factor, against human and mouse NRXN1b showed reactivity towards human and mouse NRXN1b with observed EC₅₀ values of 0.05 nM and 1 nM for human and mouse NRXN1b, respectively.

Protocol: ExpiCHO cells were grown per manufacturer’s instruction. Plasmids expressing mouse or human NRXN1b were transiently transfected into cells together with a plasmid expressing blue fluorescent protein (BFP). Control cells were transfected with plasmid expressing full-length human B7H3 together with the BFP plasmid. Two days after transfection, cells at a density of 3 x 10⁶ cells/mL were labeled with primary antibodies.

• Primary antibody: 15 µg/mL in 1 mL Dulbecco's phosphate-buffered saline (DPBS), 0.5% BSA, with 0.9 mM Ca²⁺, 0.5 mM Mg²⁺, kept at 4 °C. 50 µL of antibody added to cells and incubated on ice for 30 min.
• Washing conditions: Cells pelleted and washed twice in 0.5% DPBS, 0.5% BSA, with 0.9 mM Ca²⁺, 0.5 mM Mg²⁺.
• Secondary antibody: 2 µg/mL Alexa Fluor 647 F(ab')₂ goat anti-rabbit IgG Fc fragment (Jackson ImmunoResearch, 111-606-046) in 0.5% DPBS, 0.5% BSA, with 0.9 mM Ca²⁺, 0.5 mM Mg²⁺, 30 min, on ice.
• Detection: Labeled cells were analyzed with an Intellicyt iQue Screener Plus flow cytometer. Cells were first gated for positive BFP expression and then gated for the Alexa 647-conjugated secondary antibody.