Two-second Tip: CD45RA and CD45RO are interchangeable in peripheral blood T-cells.

When designing T-cell panels for use on peripheral blood samples, the CD45 isoforms RA and RO are really great for discriminating naive and memory cells. When coupled with another marker- like CCR7, CD27, or CD57 - you can identify subpopulations of memory cells, like central, transitional, effector. We don't really measure CD45RA and RO in the same panel, though, because they mostly have inverse expression - cells high for CD45RA are low for CD45RO, and vice versa:

You can take advantage of this in panel building. A couple of months ago, I was building another T-cell differentiation panel, and found that the only CD45RO reagent I hadn't run out of looked terrible (probably because I was scraping the bottom of the vial for reagent). Luckily, I had a different channel open and a CD45RA antibody, so I substituted that reagent in my next experiment. Score!