"Graft rejection" is when the body's immune system recognizes and attacks a transplanted organ or tissue as if it's a foreign substance or invader, causing it to fail. Full definition
Depletion of CD4 + T cells by in vivo administration of anti-CD4 monoclonal antibodies (12, 13) or deletion of the CD4 gene (14, 15) have demonstrated the importance of CD4 + T cells in corneal graft rejection. (journals.lww.com)
Both CsA and tacrolimus are T cell activation inhibitors initially developed for their systemic use in preventing graft rejection after organ transplantation. (eyespecialistsforanimals.com)
«How common chemo drug thwarts graft rejection in bone marrow transplants.» (sciencedaily.com)