TAL-1 expression in normal hemopoietic cells and neoplastic cell lines.

(A) At left is a sample from fetal liver that shows numerous scattered TAL-1–positive nuclei. At right is a sample with double staining for TAL-1 (in brown) in combination with cytokeratin (CK), transferrin receptor (TfR), or platelet glycoprotein (Plt) (all in red) that identifies the TAL-1–positive cells, many of which are intrasinusoidal (arrow), as erythroid precursors and megakaryocytes. (B) The erythroleukemic HEL cell line shows strong nuclear positivity. Nucleoli are unstained. (C) TAL-1 is also expressed in the K562 erythroid cell line, localized to discrete intranuclear bodies and often in an annular pattern (immunoperoxidase [A-C] and APAAP [A] techniques in cryostat sections [A] and cytospin preparations [B,C]; reproduced with permission from Blood137). Original magnification A left, × 100; A right, × 800; B, × 800; C, × 1000.