IMMUNOLOGY OF TRANSPLANT REJECTION
Rejection is caused largely by differences in HLA alleles between donor and recipi-ent. Immunosuppressive agents are used to prevent and mitigate rejection.
· Hyperacute rejection occurs within minutes to hours due to preformed anti-bodies in the recipient. Lymphocyte cross-matching has almost eliminated this problem.
· Acute rejection occurs in the first 6 months and may be cellular (CD8+ Tlymphocytes kill graft cells) or antibody-mediated.
· Chronic rejection occurs after months or years and may be cell-mediated orantibody-mediated. The vasculature components are targeted, and the histo-pathologic changes depend on the organ involved.