Major histocompatibility complex, class II, DR alpha, also known as HLA-DRA, binds peptides derived from antigens that access the endocytic route of antigen presenting cells (APC) and presents them on the cell surface for recognition by the CD4 T-cells. The peptide binding cleft accommodates peptides of 10-30 residues. The peptides presented by MHC class II molecules are generated mostly by degradation of proteins that access the endocytic route, where they are processed by lysosomal proteases and other hydrolases. Recombinant human HLA-DRA, fused to His-tag at N-terminus, was expressed in E.coli and purified by using conventional chromatography techniques.