Processing of CTAP-III by human skin mast cells and neutrophils. Increasing concentrations of human skin mast cells were incubated with cross-linking goat α-IgE antiserum (3 μg/mL) or left untreated for 30 minutes at 37°C (A). For comparison, increasing concentrations of human neutrophils were either incubated with fMLP or left untreated under the same conditions (B). Immediately following the stimulation period, cell samples were split and the original cell suspensions (SUSP) as well as the cell-free supernatants (SN) prepared thereof were incubated with 3 μM CTAP-III for 30 minutes (A-B). Thereafter, 2 μL cell-free supernatant of each sample and standard preparations of CTAP-III and NAP-2 (50 ng per lane) were separated by SDS-PAGE, subjected to Western blotting, and immunochemically stained to visualize CTAP-III and potential degradation products with rabbit antiserum Rα-βTG and an IRDye 800-conjugated goat α-rabbit antiserum. Data from 1 representative experiment of 3 are shown.