CD30, also known as Ki-1 antigen and TNFRSF8, is a 120 kDa type I transmembrane glycoprotein belonging to the TNF receptor superfamily. Mature mouse CD30 consists of a 264 amino acid (aa) extracellular domain (ECD) with three cysteine-rich repeats, a 27 aa transmembrane segment, and a 190 aa cytoplasmic domain. In contrast, human CD30 includes an additional 90 aa in the ECD and contains six cysteine-rich repeats. CD30 is normally expressed on antigen-stimulated Th cells and B cells. However, it is upregulated in Hodgkin’s disease (on Reed-Sternberg cells), other lymphomas, chronic inflammation, and autoimmunity. CD30 binds to CD30 Ligand/TNFSF8 which is expressed on activated Th cells, monocytes, granulocytes and medullary thymic epithelial cells. In B cells, CD30 ligation promotes cellular proliferation and antibody production in addition to the expression of CXCR4, CCL3,and CCL5. An 85 ‑ 90 kDa soluble form of CD30 is shed from the cell surface by TACE-mediated cleavage. Soluble CD30 retains the ability to bind CD30 Ligand and functions as an inhibitor of normal CD30 signaling.