I'm looking at Helios CyTOF data of virally-infected mouse brains at day 7 post-infection. I've got this large population of CD45-, CD11b+ cells. I'm pretty confident that they're negative for CD45 and not just low, so if this is the case, what could they be? Typically, microglia will have lower CD45 expression, but this population is really looking more negative than low. I don't have a ton of experience with CyTOF/Flow data analysis, so maybe I'm missing something here that's obvious. My precursory searches have not led me to an obvious candidate for CD11b+ cells that lack CD45.