Human peripheral blood lymphocytes were stained with CD45RA (clone HI100) Alexa Fluor® 647 (filled histogram) or mouse IgG2b, κ Alexa Fluor® 647 isotype control (open histogram).

Human paraffin-embedded tonsil tissue slices were prepared with a standard protocol of deparaffinization and rehydration. Antigen retrieval was done with Citrate Buffered 1X (10mM, pH 6.0) at 95°C for 40 minutes. Tissue was washed with PBS/0.05% Tween 20 twice for five minutes and blocked with 5% FBS and 0.2% gelatin for 30 minutes. Then, the tissue was stained with 10 µg/mL of Alexa Flour® 647 anti-human CD45RA (Clone HI100) antibody (red) and Brilliant Violet 421™ anti-human CD45RO (Clone UCHL1) antibody (blue) at 4°C overnight. The image was scanned with a 10X objective and stitched with MetaMorph® software.