Figure 2.

M2b polarization. The macrophage polarization toward the M2b phenotype needs two classical stimuli (ICs and LPS/IL-1). The crosslinking of FcγR by ICs triggers the activation of PI3K-, MAPK/ERK-, and NF-κB-mediated signaling pathways. To fully polarize, the binding of LPS or IL-1 to their respective receptors is also required, which then induces the activation of NFκB, PI3K/Akt, IRFs, and MAPKs. In addition, stimuli (e.g., irradiation, microRNA 122) other than the classical inducers have been described. The presence of long non-coding RNA GAS5 negatively correlates with M2b polarization. In response to irradiation exposure, the induced miRNA-122 expression leads to the degradation of GAS5, thereby favoring M2b polarization.