Monoclonal Antibody CD133–2 (AC141) Against Hematopoietic Stem Cell Antigen CD133 Shows Crossreactivity with Cytokeratin 18

Abstract

CD133 is an antigen expressed on hematopoietic progenitor cells and on some epithelial cells. We previously reported that a commercially available antibody against CD133, CD133–2/AC141, also reacted with an intracellular protein in placental trophoblasts. Here we show by 2D electrophoresis and mass spectroscopy that this reactivity is with cytokeratin 18, a cytokeratin present in most simple epithelia. Immunohistochemistry (IHC) with CD133–2/AC141 on a trophoblast cell line displayed a staining pattern typical for the cytoskeleton. Cryostat sections of stratified epithelia lacking cytokeratin 18 did not react with CD133–2/AC141. In conclusion, care must be taken not to misinterpret staining patterns using CD133–2/AC141 in IHC.