interleukin-37; FIL1 zeta; IL-1X; interleukin-1 family member 7; IL-1F7; interleukin-1 homolog 4; IL-1H; IL-1H4; interleukin-1 zeta; IL-1 zeta; interleukin-1-related protein; IL-1RP1; interleukin-23; IL-37 (IL37, FIL1Z, IL1F7, IL1H4, IL1RP1)

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Function

suppressor of innate inflammatory response & innate immune response involved in curbing excessive inflammation
- requires SMAD3
- suppresses, or reduces, proinflammatory cytokine production, including IL1A & IL6, as well as CCL12, CSF1, CSF2, CXCL13, IL1B, IL23A & IL1RN
- spares anti-inflammatory cytokines
- inhibits dendritic cell activation
proteolytically converted to the mature form by CASP1
interacts with SMAD3
binds IL18R1 with lower affinity than IL18
- does not seem to act as a receptor antagonist for IL18
does not bind IL1R1

belongs to the IL-1 family

cytoplasm, nucleus, secreted
stimulation with IL1B leads to colocalization with SMAD3 mostly in perinuclear regions
only the CASP1-cleaved mature form translocates into the nucleus upon LPS stimulation

in general, low constitutive expression, if any, in healthy tissues
high expression in inflammatory tissues, including synovial tissues from individuals with active rheumatoid arthritis
isoform A, isoform B & isoform C are expressed in testis, colon, placenta, lung & lymph node
isoform D & isoform E are found only in testis & bone marrow
only isoform A is found in brain
only isoform B is found in kidney
only isoform C is found in heart
highly induced by bacterial lipopolysaccharides (LPS) & TGFB1, more moderately by IFNG, IL18, IL1B, TNF & the dinucleotide CpG (at protein level)
constitutive expression in bone marrow macrophages is down-regulated in the presence of IL4 & CSF2
induced by phorbol myristate acetate (PMA) in different cell lines