ABSTRACT
I. BIOLOGICAL FEATURES OF HUMAN INTERFERON-y Interferon-y (IFN-y) is a type II interferon coded by a gene located on chromosome 12 and comprising three introns and four exons. The exons code for a polypeptide of 166 amino acids, 20 of which constitute the signal peptide (1-3). Although IFN-y displays no molecular homology with type I IFNs (a, J3, w, T) and it is only produced by T lymphocytes and natural killer cells, it shares with type I IFNs some important biological activities. IFN-y is, in fact, a pleiotropic cytokine with antiviral, antibacterial, and antiprotozoal activity (4). Its immunomodulatory properties entail coregulation of macrophage as well as B-cell and T-cell functions (5). IFN-y exerts its activity by binding to a species-specific glycoprotein cell surface receptor (IFN-yR) encoded by a gene located on chromosome 6. The resulting protein has a 228-amino acid extracellular domain, a 19-amino acid single transmembrane domain, and an intracellular domain of 222 amino acids (6). To be functionally active, the IFN-yR requires at least a species-specific signal-transducing factor (accessory factor 1 or IFN-y chain) encoded by a gene on chromosome 21 (7) (see Chapter 1).
