IgG抗体【知识研究】

1、IgG抗体 ANTIBODY,1,资料类,免疫球蛋白的结构,（ Structure of Ab Molecules）,2,资料类,同种异型（allotype)： 同一种属不同个体间免疫球蛋白分子所具有的不同的抗原特异性标志。,由C区决定，主要反映在Ig分子的CH和CL上的一个或数个氨基酸的差异，又称为遗传标志。,3,资料类,独特型(idiotype, Id) ： 同一个体内不同B细胞克隆产生的免疫球蛋白分子所特有的抗原特异性标志。,由超变区决定,4,资料类,IgG分子的四种亚型,IgG1,IgG4,IgG3,IgG2,5,资料类,主要以单体形式存在，抗原结合价为2价 出生后3个月开始合成，35

2、岁接近成人 血清中含量最高，占血清总Ig的75-80% 产生比较晚，是再次应答的主要抗体 半衰期最长(t 23天) 分布最广，易通过毛细血管壁，是血管外的主要抗体 唯一能通过胎盘的Ig，新生儿抗感染免疫起重要作用 激活补体 IgG13（经典），IgG4（替代） 结合细胞 吞噬细胞调理作用 NK细胞，吞噬细胞介导ADCC 结合SPA协同凝集实验,特性：又称为胎盘球蛋白,6,资料类,功能：,抗感染的主要抗体,新生儿抗感染免疫的重要抗体 介导II,III型超敏反应 介导自身免疫,7,资料类,功能,IgG抗体是反映人体免疫功能的重要指标。 根据结构的不同IgG抗体可分为4 个亚类,即IgG1, IgG

3、2, IgG3 和IgG4。 这4个亚类的生物学特性不同,因此它们在疾病的发生发展过程中发挥不同的作用.,8,资料类,功能,针对细菌和病毒抗原产生的抗体中(例如破伤风毒素或膜蛋白成分都是T细胞依赖型抗原) , IgG1占主导地位,有时伴随IgG3的产生, IgG2水平较低。,9,资料类,功能,特异性皮炎( atop ic dermatitis)是一种慢性复发性皮肤炎症疾病,特异性皮炎患者血清中针对花粉或尘螨的特异性IgE和IgG4水平升高。,10,资料类,功能,青霉素过敏患者血清中, IgG3 和IgG4 阳性的百分率分别为28. 05% , 13. 39%和12. 80% ,表明IgG3和I

4、gG4抗体在青霉素超敏反应中发挥重要作用。,11,资料类,IgG抗体与HDN,各亚类激活补体经典途径的能力为IgG3 IgG1 IgG2 , 所以IgG3 在各亚类中溶血性最强, 发生的HDN最严重。,12,资料类,IgG抗体与HDN,从患儿及患儿母亲血清中IgG亚类含量的构成来看, 虽均以IgG1 为主, 但患儿体内IgG1 的比例较母亲体内高, 而其他3种亚类均略低于母体, 说明了IgG1 含量升高对新生儿溶血病有着更重要的作用。,13,资料类,IgG抗体与HDN,孕妇血清中IgG特异性抗体效价持续升高, 并且IgG1 亚类含量也显著高者, 可预报新生儿溶血病的发生, 当IgG3 也显著升

5、高时, 提示新生儿溶血严重。,14,资料类,The immune system consists of two functional components: Innate immune system Prevents penetration and spread of infectious agents by a variety of physical, biochemical and cellular barriers (skin, mucosa, lysozymes, complement, phagocytes) Adaptive immune system Develops a spe

6、cific immunological memory after the first attack. This leads to a stronger, faster and more effective response upon renewed contact with the same agent. Lymphocytes and immununoglobulins are the key elements Humoral immunity B-cells plasma cells immunoglobulins Cell mediated immunity T-cells Helper

7、 T-cells & Cytotxic T-cells,15,资料类,In humoral immunity B-cells recognize soluble or cell surface antigens (on extracellular microbes ) and differentiate into antibody secreting plasma cells. In cell-mediated immunity helper T-cells recognize antigens on the surfaces of antigen-presenting cells and s

8、ecrete cytokines, which stimulate B-cells and T-cells. Cytotoxic T-cells recognize antigens on infected cells and kill these cells.,16,资料类,17,资料类,18,资料类,19,资料类,20,资料类,relative serum concentrations IgG1 IgG2 IgG3 IgG4 differences in flexibility of the IgG3 IgG1 IgG4 IgG2 hinge region differences in b

9、iological properties Fab part + antigen effector functions via Fc part activation of complement IgG3 IgG1 IgG2 IgG4 induction of phagocytosis FcgRI CD 64: IgG3 IgG1 IgG4 (opsonisation)FcgRII CD 32: IgG3 IgG1 IgG2 binding to FcgR of effector cells FcgRIII CD 16: IgG3 = IgG1 CD 16: neutrophil granuloc

10、ytes, monocytes, macrophages , NK cells CD 32: monocytes, subpopulation of macrophages, granulocytes, eosinophils, B cells CD 64: monocytes, activated granulocytes,21,资料类,IgG1 Main response to virall and bactteriall prottein anttigen exposure Immune response tto capsulle pollysaccharide Acttivattiio

11、n compllementt Efffiicientt binding tto llymphocyttes via Fc recepttor Auto-antibodies IgG2 Predominantimmune response tto pollysacchariide antigens of bactteria such as pneumococci group A sttreptococci and Haemophillus iinfflluenzea IgG3 High-affiniittyantbodies tto protein antigens strongest comp

12、llementt acttiivattiion efficientt bindiing to lymphocytes viia Fc recepttor auto-antibodiies IgG4 Responses to chronic allergic stimullation Immune response tto alergens even after hyposensitization Blocking the IgE response,22,资料类,decrease of one IgG subclass + increase of other subclass total IgG

13、 level may normal. determination of IgG subclass levels is important, even when the total IgG level is within or only slightly below the reference range of healthy individuals. IgG subclass deficiency is not excluded by a normal or even high total IgG concentration! The finding of a decreased level

14、of one of the IgG subclasses can never provide a definite diagnosis, but should rather be considered as an indication of a disturbance of the immune system, requiring further diagnostic investigation.,23,资料类,Autoimmune / atopic diseases Bronchial asthma IgG2, IgG3 Diabetes variable Idiopathic thromb

15、ocytopenic purpuraIITP IgG2, IgG4 Systemic lupus erythematosus IgG3, IgG4 Immunodeficiencies Bone marrow transplantation IgG2, IgG4 CVID (common variable immunodeficiency) IgG1, IgG2, IgG4 High-dose corticosteroids IgG2, IgG3 HIV infection IgG2, IgG4 Chemotherapy, radiation exposure IgG2 Wiskott-Aldrich disease IgG4 Infections Otitis media (pneumo