Immunogen sequence: PKPVSKMRMA TPLLMQALPM GALPQGPMQN ATKYGNMTED HVMHLLQNAD PLKVYPPLKG SFPENLRHLK NTMETIDWKV FESWMHHWLL FEMSRHSLEQ KPTDAPPK. HLA-DR, like other MHC class II molecules, is a transmembrane glycoprotein composed of a 36 kDa alpha chain (DRA)