Immunosuppressant drugs aren't used for the treatment of AHTRs. The antibodies are already present and acting, which is the issue.

A patient's blood is grouped and then screened for 'clinically significant' antibodies to many of the common red cell antigens. (There are tons more than ABO/RhK) Antigen negative blood is provided dependent on the outcome of the antibody screen/panel. A patient that has a positive antibody screen also has to have all units fully crossmatched against their plasma before provision.

It's a different story for solid organ transplants, they have a ton more testing requirements e.g. HLA typing and also require immunosuppression.