The HLA Class II sequences included in this compilation are taken from publications listed in the papers: Nomenclature for factors of the HLA system, 1991 (1), Nomenclature for factors of the HLA system, 1990 (2), and Nomenclature for factors of the HLA system, 1989 (3). Where discrepancies have arisen between reported sequences, the original authors have been contacted, where possible, and necessary amendments to published sequences have been incorporated into this alignment. Future sequencing may identify errors in this list and we would welcome any evidence that helps to maintain the accuracy of this compilation. In the sequence alignments, identity between residues is indicated by a hyphen (-). An unavailable sequence is indicated by an asterisk (*), gaps in the sequence are inserted to maintain the alignment between different alleles showing variation in amino acid number.