MicroRNA-155 (miR-155) expression promotes inflammatory responses in macrophages. Activation of macrophages with lipopolysaccharide (LPS) elevates miR-155, while the anti-inflammatory cytokine interleukin-10 (IL10) reduces miR-155 levels. MiR-155 exists in two forms, miR-155-5p and miR-155-3p, produced from the precursor of miR-155 (pre-miR-155). MiR-155-5p is the most abundant strand in activated macrophages, but in response to LPS, the miR-155-3p level is upregulated first, followed by miR-155-5p later. We have previously identified CELF2 protein which interacts with pre-miR-155 and impairs miR-155-5p expression. We now show that CELF2 only regulates the miR-155-5p expression and that another protein FUBP1 controls miR-155-3p levels in response to LPS and IL10.