Analysis of tmTNF-α expression in normal human blood cells and tissues. (A) Expression of tmTNF-α by various types of white blood cells in PB from healthy donors (n = 4) was analyzed by FCM. The types of white blood cells were gated using the indicated antibodies. (B) Various lineages of hematopoietic stem/progenitor cells in healthy BM (n = 5) were gated using the indicated antibodies and assessed for tmTNF-α expression. (C) Expression of tmTNF-α was examined by immunohistochemical staining of histology sections from various normal (magnification, ×100 and ×400) and malignant human tissues (magnification, ×400). Immunoreactive tmTNF-α (black arrows) was readily detectable in BM sections with de novo AML or ALL, but was absent or only weakly detected in normal human tissues (2 sections per tissue for each tissue microarray).