Primary antibodies: anti-MIIA antibody (rabbit) (1:1000; M8064, Sigma Aldrich), anti-MIIB antibody (N-17) (rabbit) (1:1000; 3404S, Cell Signaling), and anti-DIA1 antibody (E-4) (mouse) (1:100; SC-373807, Santa Cruz Biotechnology). β-Actin was used as a loading control (1:10,000; 612656; Purified Mouse Anti-Actin Ab-5, BD Biosciences).
Secondary antibodies: anti-mouse immunoglobulin G (IgG), horseradish peroxidase (HRP)–linked antibody (1:2000; 7076S, Cell Signaling), and anti-rabbit IgG, HRP-linked antibody (1:2000; 7074S, Cell Signaling).