Nelson K A
Puget Sound Blood Center and Program, Immunogenetics Laboratory, Seattle, WA 98104-1256, USA.
Clin Orthop Relat Res. 1996 May(326):35-42. doi: 10.1097/00003086-199605000-00005.
Immunologic rejection of tissue grafts follows recognition of donor alloantigens; either those resulting from ABO incompatibility of those encoded by the human major histocompatibility complex, HLA. Alloantigens encoded by HLA are present on membrane proteins that are expressed constitutively by tissues or whose expression can be induced by cytokines released during inflammation. Genes of the HLA complex are highly polymorphic resulting in variations in amino acid sequence that shape the peptide binding pocket of HLA molecules and define the complementary structure that interacts with the T lymphocyte receptor for antigen. Variants of HLA proteins expressed by the allografts that are not expressed by the recipient can stimulate the immune response to the allograft resulting in rejection both by humoral antibody and through attack by T lymphocytes. Class II HLA antigens on donor cells can stimulate these responses directly by contact with recipient T cells. However, rejection also may result when HLA antigens are released from the graft, processed to peptides, and presented to recipient T cells by cells expressing recipient HLA Class II molecules. Rejection can be avoided by preventing activation of T lymphocytes, by minimizing differences in HLA proteins between recipient and donor or by avoiding preexisting responses to donor HLA antigens.
组织移植物的免疫排斥反应发生在供体同种异体抗原被识别之后；这些抗原要么源于ABO血型不相容，要么源于人类主要组织相容性复合体HLA所编码的抗原。HLA编码的同种异体抗原存在于膜蛋白上，这些膜蛋白由组织组成性表达，或者其表达可由炎症期间释放的细胞因子诱导。HLA复合体的基因具有高度多态性，导致氨基酸序列发生变化，从而塑造HLA分子的肽结合口袋，并定义与抗原T淋巴细胞受体相互作用的互补结构。同种异体移植物表达的而受者不表达的HLA蛋白变体可刺激对同种异体移植物的免疫反应，导致体液抗体介导的排斥反应以及T淋巴细胞的攻击。供体细胞上的II类HLA抗原可通过与受者T细胞接触直接刺激这些反应。然而，当HLA抗原从移植物中释放出来，加工成肽，并由表达受者HLA II类分子的细胞呈递给受者T细胞时，也可能导致排斥反应。通过防止T淋巴细胞激活、尽量减少受者和供者之间HLA蛋白的差异或避免对供者HLA抗原的预先存在的反应，可以避免排斥反应。
