The Anti-PTK7 (CCK-4) antibody (clone 188B) recognizes human protein tyrosine kinase-7 (PTK7). PTK7, also known as colon carcinoma kinase-4 (CCK-4), is a receptor protein tyrosine kinase (RPTK)-like molecule that contains a catalytically inactive tyrosine kinase domain.1,2 PTK7 was identified to be important for neural development as a regulator of planar cell polarity, being required for convergent extension movement and neural tube closure.3 Using the Anti-PTK7 (CCK-4) antibody, PTK7 expression was recently analyzed on blood and bone marrow cells. PTK7 was shown to be expressed on plasmacytoid dendritic cells, CD141 (BDCA-3)high type-2 myeloid dendritic cells, and CD34+ hematopoietic progenitor cells (HPCs). PTK7 was detected on early (CD34+ CD133+) and late (CD34+ CD133–) HPCs. In tonsils, PTK7 was also found on some T cells.
Human peripheral blood mononuclear cells (PBMCs) were stained with Anti-PTK7 (CCK-4) antibodies as well as with CD303 (BDCA-2), CD141 (BDCA-3), or CD34 antibodies and analyzed by flow cytometry using the MACSQuant® Analyzer. Tandem Signal Enhancer has been used to increase binding specificity of tandem-dye–conjugated antibodies. Cell debris and dead cells were excluded from the analysis based on scatter signals and propidium iodide fluorescence or 4',6-diamidino-2-phenylindole (DAPI) fluorescence, as in the case of tandem conjugates. Plasmacytoid dendritic cells (PDCs) are identified by CD303 (BDCA-2), type-2 myeloid dendritic cells (MDC2s) by CD141 (BDCA-3), and hematopoietic stem cells (HPCs) by CD34 expression.