Human Mouse
  Name Classically activated macrophages Ly6chigh
Classically Activated Function Phagocytic and microbial activity Produce pro-inflammatory cytokines such as TNF-α
Low pro-inflammatory cytokine production (IL-10, TNF-α, IL-12 etc.)  
Main IL-10 Producer when stimulated with S. aureus  
Production of ROS  
Frequency 90-95% of circulating monocytes 60% of circulating monocytes
Markers CD14high Ly6chigh
CD16neg CD11b+
Low levels of MHC-II, ICAM-1  
CD86, CD64  
Intermediate levels of CD11b  
Cytokine Receptors CCR2high, CX3CR1low CCR2high, CX3CR1low
Intermediate Name Intermediate  
Function Pro-inflammatory: Actively produce TNF-α (in response to LPS), IL-1β, IL-6 and IL-10  
Phagocytic  
Frequency Minor sub-population  
Markers CD14high, CD16int  
High levels of MHC-II, ICAM-1, CD86, CD11b  
Intermediate levels of CD163, CD64 and CD11c  
Cytokine Receptors CCR2low, CX3CR1high  
Alternatively activated Name Alternatively activated Alternatively activated, Ly6Clow
Function Anti-inflammatory: Constitutively produce IL-1RA  
Frequency 5-10% of circulating monocytes 40% of circulating monocytes
Markers CD14low, CD16high Ly6Clow
High levels of CD86 and CD11c  
Intermediate levels of MHC-II  
ICAM-1  
Low levels of CD11b, CD64 and CD163  
Cytokine Receptors CCR2low, CX3CR1high CCR2low, CX3CR1high
Table 2: Main monocyte populations in human and mouse. Mouse monocytes are divided into classically activated M1 monocytes and alternatively activated M2 monocytes. M1 monocytes express high levels of Ly6C and low levels of CX3CR1 and are known for producing proinflammatory cytokines such as TNF-α. M2 monocytes express low levels of Ly6C and high levels of CX3CR. Human monocytes are divided into three subgroups, where the classical group is called CD14highCD16neg. They express high levels of CCR2 but lack CX3CR1 surface expression. Using the mouse homology they are M1-like but functionally they resemble M0-like monocytes. The intermediate CD14highCD16int monocytes