I think that macrophage subtypes can be distinguished by the expression of costimulatory molecules, PRRs and/or MHC II. For starters, the M1 subtype, with inflammatory effector functions, expresses among others CD80/86, TLR4, TLR2 and highly the MHC II molecule. The M2a subtype has elevated expression of CD206 and expresses CD163, the M2b expresses CD86 and is positive for MHC II while M2c expresses CD163, TLR1 and TLR8.
Of course the above markers correspond to human macrophage subsets.