<prompt> Most important HLA for organ transplantation and tissue typing:HLA-AHLA-BHLA-CHLA-D  <response>: Ans. d HLA-DRef: Bailey 26th edition, Pages 1409-1412 HLA- A, B, DR are the most important antigens in transplant HLA antigens are the most common cause of graft rejection HLA- DR is the most important of all Anti HLA antibodies causes hyper acute rejection. 