Flow cytometric detection of tryptase in AML cells.

Multicolor flow cytometry staining was performed in one patient with tryptase⁺ AML (A), 2 normal donors (B,C), and one patient with AML in complete remission (D) using antibodies against tryptase, a PE-labeled CD34 mAb, and a PerCP-labeled CD45 mAb. Multicolor staining for cytoplasmic tryptase (versus isotype-matched control) and surface antigens (CD34, CD45) was performed as described in the text. As visible, the CD34⁺ blast cells in the patient with AML showed clear expression of cytoplasmic tryptase (A). In contrast, tryptase was consistently negative in CD34⁺ bm cells in normal donors (B,C) or in the patient with tryptase⁺ AML in complete remission (D) without evidence of tryptase-positive (residual) subsets of cells.