CD4+ T 細胞以及IFN-γ在Zap-70突變鼠之自體抗體反應所扮演的角色

Abstract

P358小鼠為ENU的誘導產生的突變小鼠，其ZAP70蛋白激酶中發生了單一的氨基酸置換，第563號半胱胺酸(cysteine)被置換成絲氨酸(serine)。此小鼠於週齡五週大即產生自體免疫抗體，故給予小鼠名稱“Sap”意指“血清抗體陽性”。此研究利用免疫螢光染色法檢測血清中的抗體和沉積在腎臟腎小球的免疫球蛋白以及西方墨點法來分析隨著時間的推移，自體抗體特性的變化。Sap小鼠有著接近系統性紅斑狼瘡疾病的症狀，具有大量的自體抗體在血清內和免疫複合物沉積在腎絲球中。Sap小鼠在週齡五週大時主要產生抗胞質抗體, 週齡八週以上主要產生抗核抗體，隨著年齡變化，Sap小鼠增加自體抗體總量和認識的抗原種類。抗核抗體主要屬於IgG2a亞類，而形成的免疫複合物多數為IgM。在CD4+ T細胞及γ-干擾素缺失的Sap小鼠中，IgG2a抗核抗體的消失和免疫複合物沉積量降低，證明了CD4+ T細胞及γ-干擾素在Sap小鼠的自身免疫反應的重要性。將Sap小鼠的CD4 T+ 細胞過繼轉移(adoptive transfer)至Sap-CD4-KO小鼠體內可成功誘導抗核抗體的產生但是若過繼轉移至Sap-IFN-γ-KO小鼠體內則無法產生抗核抗體，然而仍然可見抗胞質抗體。此研究證明了CD4+ T細胞和γ-干擾素在誘發抗核抗體反應中扮演重要角色，並提供了除了CD4+ T細胞以外由其他細胞提供γ-干擾素主要來源的可能性。

An ENU-induced mutant mouse with a point mutation in the Zap70 gene was studied. This mutant Zap70 gene encodes a Zap70 protein with a single C to S amino acid substitution at residue 563. This Zap70 mutant mouse spontaneously produced autoantibody and was named “Sap” for “serum autoantibody positive.” The autoantibody response in Sap mice, as a function of age, was characterized by immunofluorescence, Western blotting, and immune complex deposition techniques. Sap mice at 5 wks of age made primarily anti-cytoplasmic autoantibodies. Sap mice over 8 wks of age, on the other hand, made predominantly anti-nuclear autoantibodies (ANA), most of which were of the IgG2a isotype. Sap mice also displayed glomeruli-associated immune complex deposition, most of which were of the IgM isotype. IgG2a ANA and immune complex deposition responses were lost in Sap-CD4-KO and Sap-IFN-γ-KO mice. Adoptive transfer of Sap CD4+ T cells restored the deficient ANA response in Sap-CD4-KO but not Sap-IFN-γ-KO hosts. Despite the loss of ANA, anti-cytoplasmic autoantibody response was still observed in Sap-IFN-γ-KO mice. These results clearly show the key roles played by CD4+ T cells and IFN-γ in the induction of the ANA response. They also implicate the importance of cells other than CD4+ T cells as the provider of IFN-γ in the induction of the ANA response.