Osei A, Uttenreuther-Fischer M M, Lerch H, Gaedicke G, Fischer P
Laboratory of Molecular Biology, Charité Children's Hospital, Humboldt University, Berlin, Germany.
Arthritis Rheum. 2000 Dec;43(12):2722-32. doi: 10.1002/1529-0131(200012)43:12<2722::AID-ANR12>3.0.CO;2-N.
To perform a comparative analysis of 1) intravenous Ig (IVIG)-bound Fab fragments from a patient with autoimmune thrombocytopenia that had progressed to systemic lupus erythematosus (SLE) and 2) IVIG-selected Fabs from an SLE patient without thrombocytopenia.
IVIG preparations have been successfully used to treat certain cases of autoimmune thrombocytopenia and SLE. Specific interactions of IVIG with the components of the immune system are not well characterized. To investigate these, we had previously cloned a large number of phage-displayed IgG Fab fragments, derived from 3 patients with autoimmune thrombocytopenia, that were specifically bound by IVIG molecules during panning. Many of these Fabs reacted with platelets. Sequencing revealed that the most frequently used VH germline gene segments of all IVIG-bound Fabs were 3-23 and 3-30/3-30.5. One patient's autoimmune thrombocytopenia had progressed to SLE. Using the same cloning and panning procedures, we performed a comparative analysis of this patient's IVIG-bound Fab fragments and the IVIG-selected Fabs from an SLE patient without thrombocytopenia.
We observed an exclusive selection of antibodies derived from 3-23 and 3-30/3-30.5 germline segments. In contrast to the Fab fragments from the autoimmune thrombocytopenia patient who developed SLE, none of the IVIG-selected Fabs from the SLE patient without thrombocytopenia bound to thrombocytes.
Our results suggest a preferential interaction of a subfraction of IVIG-representative of normal Ig repertoires-with antibodies and B cell receptors derived from these 2 gene segments. Importantly, these are the most frequently rearranged VH germline genes among human B cells. This kind of interaction is characteristic of a B cell superantigen, since light chains, antigen specificity, and the high variation in the third complementarity-determining region 3 showed little influence on the selection of 3-23- or 3-30/3-30.5-derived Fabs by IVIG. However, at least some of the contact residues on Fabs for IVIG appear to be different from those for staphylococcal protein A and human immunodeficiency virus gp 120. The IVIG-selected Fabs may now be used to clone antibodies representative of this IVIG subfraction to study their possible regulatory influence on the B cell repertoire during normal development and disease.
对1）一名自身免疫性血小板减少症已进展为系统性红斑狼疮（SLE）患者的静脉注射免疫球蛋白（IVIG）结合的Fab片段，以及2）一名无血小板减少症的SLE患者的IVIG筛选的Fabs进行比较分析。
IVIG制剂已成功用于治疗某些自身免疫性血小板减少症和SLE病例。IVIG与免疫系统成分的特异性相互作用尚未得到充分表征。为了研究这些，我们之前克隆了大量源自3名自身免疫性血小板减少症患者的噬菌体展示IgG Fab片段，这些片段在淘选过程中被IVIG分子特异性结合。其中许多Fabs与血小板反应。测序显示，所有IVIG结合的Fabs中最常用的VH胚系基因片段是3-23和3-30/3-30.5。一名患者的自身免疫性血小板减少症已进展为SLE。使用相同的克隆和淘选程序，我们对该患者的IVIG结合的Fab片段与一名无血小板减少症的SLE患者的IVIG筛选的Fabs进行了比较分析。
我们观察到仅筛选出来自3-23和3-30/3-30.5胚系片段的抗体。与发展为SLE的自身免疫性血小板减少症患者的Fab片段不同，无血小板减少症的SLE患者的IVIG筛选的Fabs均未与血小板结合。
我们的结果表明，代表正常Ig库的IVIG亚组分与源自这两个基因片段的抗体和B细胞受体之间存在优先相互作用。重要的是，这些是人类B细胞中最常重排的VH胚系基因。这种相互作用是B细胞超抗原的特征，因为轻链、抗原特异性以及第三互补决定区3的高度变异性对IVIG选择源自3-23或3-30/3-30.5的Fabs影响很小。然而，Fabs上与IVIG结合的至少一些接触残基似乎与葡萄球菌蛋白A和人类免疫缺陷病毒gp 120的不同。现在，IVIG筛选的Fabs可用于克隆代表该IVIG亚组分的抗体，以研究它们在正常发育和疾病过程中对B细胞库可能的调节影响。
