Induction of histamine release in MCs by CD2 stimulation.

MCs were isolated from the BM of a patient with SM and incubated with control medium (co), the T11-1–specific mAb 39C1.5 (3 μg/mL), T11-2–specific mAb 6F10.3 (3 μg/mL), the T11-3–specific mAb VIT13 (3 μg/mL), and combinations of mAbs as indicated. After 30 minutes of incubation (37°C), cells were centrifuged and the cell-free supernatants examined for the presence of histamine by radioimmunoassay. As visible, a combination of mAbs against T11-1 and T11-3 as well as a combination of T11-2– and T11-3–specific mAbs resulted in a marked increase in histamine release above control. A slight increase was also observed when cells were incubated with only one mAb. Corresponding results were obtained in a second mastocytosis patient. By contrast, in 2 reactive BMs, neither the antibody combinations nor the single mAb induced histamine release above control. Results represent the mean ± SD of triplicates.