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. 2024 Jun 8;25(12):6367. doi: 10.3390/ijms25126367

Figure 3.

Figure 3

Peptide competition of the CFTR-specific antibody Ab 596. In order to determine specific binding of the CFTR-specific antibody Ab 596 used in the previous experiments, we performed a peptide competition experiment. Lysates of stimulated CD4+ T cells and differentiated THP1 cells were immunoblotted with the antibody Ab 596, and either a surplus of the epitope-specific peptide H-WPSGGQMT-OH, PBS only, 16HBE14o-, or HEK cells served as positive and negative controls. As expected, peptide competition completely blocked the CFTR signal (B- and C-band) in 16HBE14o- cells. In contrast, the previously observed bands (red arrows) at 95 kDa in CD4+ T cells were not blocked by the peptide. Another immunoreactive narrow band of the size of CFTR-C (purple arrow) was not blocked as well, revealing the non-specific binding of the antibody. Faint signals seen for differentiated THP1 cells were not blocked, and no signals were detected for negative control HEK cells with the AB596. Source data for this figure are provided in Supplementary Figure S3, which shows the exposures side-by-side for both membranes.