Intracellular Staining by Flow Cytometry
|Detection of CXCL4/PF4 in Human Immature Dendritic Cells by Flow Cytometry. Human immature dendritic cells were stained with Mouse Anti-Human CXCL4/PF4 Fluorescein-conjugated Monoclonal Antibody (Catalog # IC7952F, filled histogram) or isotype control antibody (Catalog # IC0041F, open histogram). To facilitate intracellular staining, cells were fixed with Flow Cytometry Fixation Buffer (Catalog # FC004) and permeabilized with Flow Cytometry Permeabilization/Wash Buffer I (Catalog # FC005). View our protocol for Staining Intracellular Molecules.|
CXCL4, also known as Platelet Factor 4 (PF4), is an 8 kDa CXC chemokine that is stored in platelet alpha -granules as a homotetramer and secreted abundantly during platelet activation. Human CXCL4 is a 101 amino acid (aa) protein with a 32 aa signal sequence and a 70 aa mature protein that includes granule targeting and heparin-binding sequences. CXCL4 has homology with IL-8 and beta -thromboglobulin and can form heteromultimers with IL-8. Mature human and mouse CXCL4 share 76% aa identity. The active protein consists of a tetramer composed of individual CXCL4 subunits. Megakaryocytes synthesize CXCL4 and store it as tetramers in alpha -granules. The CXCL4 tetramers are secreted by activated platelets and can be measured at micromolar levels in serum. In contrast to other CXC chemokines, CXCL4 lacks chemotactic activity for polymorphonuclear granulocytes. CXCL4 does not contain an ELR motif. However, many other functions have been observed for CXCL4. CXCL4 is involved in monocyte survivial and differentiation into macrophages, has anti-angiogenic activity and promotes granule Protein C activation. CXCL4 has been demonstrated to inhibit the binding of FGF-2 to high-affinity receptors and its subsequent internalization. Cell surface neutrophil chondroitin sulfate chains serve as CXCL4 binding sites; affinity is controlled by the degree of sulfation of these chains.