Expression of I antigen and IGnT genes in erythroid differentiation of K-562 cells. (A) Flow cytometry analysis for I antigen expression. K-562 cells were cultured in medium supplemented with 1 mM of sodium butyrate for 2 days to induce erythroid differentiation. Expressions of the cell-surface I antigens on the K-562 cells with or without sodium butyrate treatment (indicated as +SB and −, respectively) were analyzed using flow cytometry and detected with monoclonal anti-I antibody (mAb OSK14; 1:5 dilution), with the bound mAb on the cell surfaces revealed by FITC-conjugated goat anti-human IgM (1:200 dilution). The open and shaded areas represent results obtained from cells incubated with anti-I mAb and FITC-conjugated secondary antibody, and with FITC-conjugated secondary antibody only, respectively. (B) Expression profiles for the IGnT transcripts. Real-time PCR was used to quantify the IGnTA, IGnTB, IGnTC, and β-actin transcripts in the cDNA samples. The quantities of the IGnT transcripts were normalized to that of β-actin transcript in each sample. Data were obtained from 3 detections; standard deviations are shown.