Hey everyone,

I have the following situation in a murine bacterial CNS infection model:

We gated whole brain cell suspensions for CD45/CD11b and afterwards for CX3CR1/Ly6C.

We observed one population which is CD45loCD11b+CX3CR1+Ly6Clo/- . So I would say, that these are (surveying) microglia - so far so good.

But there's another population which is CD45hiCD11bhi

First thought: ok, that are most likely inflammatory monocytes and macrophages. But as we looked at the CX3CR1 and Ly6C expression pattern we could see two distinct populations.

To my knowledge and what I've read so far in literature is, that inflammatory moncytes, when entering the brain, should switch their status from CX3CR1+Ly6C-/lo to CX3CR1-Ly6Chi. 

So i would interpret the CD45hiCD11bhiCX3CR1-Ly6C+/hi as inflammtory monocytes and CD45hiCD11bhiCX3CR1+Ly6C- as activated microglia. But I cant find anything about CD45hiCD11bhi microglia. So what are these? Highly activated microglia or patrolling monocytes which didn't change their phenotype yet from CX3CR1+Ly6Clo to CX3CR1-Ly6Chi after entering the brain?

Further, I can't do another round of FACS, so looking for CCR2,CD68 etc can't be done.

Thanks for your help,

Dennis