Husebye Eystein S, Bratland Eirik, Bredholt Geir, Fridkin Mati, Dayan Molly, Mozes Edna
Department of Immunology, The Weizmann Institute of Science, Rehovot, Israel.
Endocrinology. 2006 May;147(5):2411-6. doi: 10.1210/en.2006-0018. Epub 2006 Feb 23.
The steroidogenic enzyme 21-hydroxylase (21OH) is the main autoantigen in autoimmune primary adrenal failure (Addison's disease). Autoantibodies against 21OH are immunological markers of an ongoing autoimmune process but are not directly involved in the tissue destruction. Autoreactive T cells are thought to mediate tissue damage, but the T cell antigen(s) has not been identified. To find out whether 21OH contains important immunodominant epitopes for T cells, we first immunized BALB/c and SJL inbred mouse strains with recombinant 21OH and showed that lymph node cells proliferated effectively following in vitro stimulation with recombinant 21OH (stimulation indices (SI) 20-40). We further synthesized a series of peptides based on 21OH with amino acid sequences with propensity to bind to major histocompatibility complex class II molecules. Only a few peptides could trigger lymphocytes of 21OH-primed mice to proliferate. One of these, 21OH (342-361), stimulated effectively 21OH-primed lymph node cells of SJL mice (SI = 4-8) and also, although to a lesser extent, of BALB/c mice (SI = 2.5). When SJL mice were immunized with 21OH (342-361), the immunizing peptide as well as peptide 21OH (346-361) triggered a significant proliferative response (SI = 24). A peptide from another part of 21OH, namely 21OH (191-202), did not stimulate the 21OH (342-361)-primed cells. Moreover, stimulation of lymph node cells of mice immunized with 21OH (342-361) with 21OH resulted in a significant proliferative response. We conclude that 21OH (342-361) is an immunodominant determinant for T cells in SJL and probably BALB/c mice. 21OH (342-361) corresponds to the substrate binding site of the enzyme. The p342-361 region may be involved in the pathogenesis of autoimmune adrenal failure in humans.
类固醇生成酶21-羟化酶（21OH）是自身免疫性原发性肾上腺功能不全（艾迪生病）的主要自身抗原。针对21OH的自身抗体是正在进行的自身免疫过程的免疫标志物，但不直接参与组织破坏。自身反应性T细胞被认为介导组织损伤，但T细胞抗原尚未确定。为了确定21OH是否含有对T细胞重要的免疫显性表位，我们首先用重组21OH免疫BALB/c和SJL近交系小鼠，结果显示，体外经重组21OH刺激后，淋巴结细胞有效增殖（刺激指数（SI）为20 - 40）。我们进一步基于21OH合成了一系列具有易于与主要组织相容性复合体II类分子结合的氨基酸序列的肽段。只有少数肽段能触发经21OH免疫的小鼠淋巴细胞增殖。其中之一，21OH（342 - 361）能有效刺激SJL小鼠经21OH免疫的淋巴结细胞（SI = 4 - 8），对BALB/c小鼠的刺激作用虽较弱（SI = 2.5）。用21OH（342 - 361）免疫SJL小鼠时，免疫肽以及肽段21OH（346 - 361）引发了显著的增殖反应（SI = 24）。来自21OH另一部分的肽段，即21OH（191 - 202），不能刺激经21OH（342 - 361）免疫的细胞。此外，用21OH刺激经21OH（342 - 361）免疫的小鼠淋巴结细胞会导致显著的增殖反应。我们得出结论，21OH（342 - 361）是SJL小鼠以及可能在BALB/c小鼠中T细胞的免疫显性决定簇。21OH（342 - 361）对应于该酶的底物结合位点。p342 - 361区域可能参与人类自身免疫性肾上腺功能不全的发病机制。
