Immunohistochemical and immunocytochemical detection of tryptase.

Expression of tryptase in AML blasts was demonstrated by immunostaining experiments using the anti-tryptase mAb G3 and bm sections or cytospin preparations (isolated MNCs). Immunostaining experiments were performed as described in the text. (A) A tryptase-stained bm section in a patient with AML M4eo (serum tryptase level, 881 ng/mL). As visible, many immature myeloid cells (blasts) in the bm reacted with anti-tryptase antibody. In other patients, only a few blasts were found to react with mAb G3. (B) The reactivity of blast cells with this mAb in a case of AML M2 (serum tryptase level, 41.6 ng/mL). In patients with AML without elevated tryptase and those with ALL, bm blasts appeared to be tryptase⁻ by immunohistochemistry. (C) A bm section in a patient with ALL (serum tryptase level, 8.9 ng/mL) stained with mAb G3. Immunocytochemistry confirmed tryptase expression in AML blasts. (D) A cytospin preparation of bm MNCs prepared in a patient with AML M4eo (the same as in panel A). As visible, most of the AML blasts reacted with anti-tryptase mAb G3, confirming the immunohistochemical staining result (A). Note that most of the G3-reactive material is localized in the cytoplasm of AML blasts.