May play an important role in the control of the immune response and during pregnancy. Binds 1 zinc ion per subunit. Expressed highly in the small intestine and appendix, moderately in lymph node, mucosal lining of the colon, thymus, spleen and very weakly in the bone marrow. Predominantly expressed in dendritic cells (DC) of the germinal center. Weakly expressed in monocyte and highly expressed in macrophage. Absent in immature DC. Induced during DC maturation and up-regulated in response to T-cell signals. In macrophage up-regulated by bacterial lipopolysaccharides (LPS). Up-regulated by 1-alpha,25-dihydroxyvitamin D3 during differentiation of primary monocyte into macrophage.