Colocalization of matriptase and uPAR on THP-1 cells. THP-1 cells were fixed with formaldehyde and stained for (A) uPAR using monoclonal antibody R4 and (B) matriptase using polyclonal antibody IM1014. Detection of uPAR and matriptase was with fluorescein- and rhodamine-conjugated secondary antibodies, respectively. (C) Nuclear staining with DAPI. (D) The merged images with uPAR in green, matriptase in red, and DAPI in blue. The specificity of the observed colocalization was demonstrated in control experiments, with cells stained for matriptase and β₁-integrin, in which no colocalization was observed in merged images (data not shown).