Contrast acute rejection and chronic rejection

Question

What will be an ideal response?

Answer 1

Acute rejection occurs within a few days of transplantation and is mediated by an alloreactive CD4 and CD8 T cell-mediated adaptive immune response by the recipient against the ‘foreign' HLA molecules on the graft and involves the direct pathway of recognition. In contrast, chronic rejection occurs months to years after transplantation; it is mediated by anti-HLA class I and anti-HLA class II alloantibodies and involves the indirect pathway of recognition. CD4 T cells are first activated by recipient dendritic cells presenting donor-derived HLA class II allotypes of the recipient. These activated CD4 T cells in turn activate B cells, which are also presenting donor-derived allogeneic HLA peptides. This cognate interaction results in the production of anti-HLA class I (and also anti-HLA class II) antibodies.