In which passage do you test the cell type-specific markers?

Cell type-specific markers are usually determined one passage after thawing. Example: After thawing, HUVEC are in P1. Markers (CD31 expression, Dil-Ac-LDL uptake) are tested in P2. Please note: Cells that are frozen directly after isolation (blood cells) are tested directly after thawing with no further culturing step.