母胎界面自然杀伤细胞的研究进展

自然杀伤(natural killer,NK)细胞是母胎界面丰度最高的免疫细胞,在妊娠早期的子宫蜕膜中大量积聚.研究表明母胎界面NK细胞具有独特表型和功能,在妊娠期免疫耐受调节、子宫内膜蜕膜化、滋养细胞侵袭、子宫螺旋动脉重塑、胎盘形成和胎儿生长、发育等多方面都发挥关键作用,但是其在妊娠中的功能及其作用机制还有待深入研究...     

母-胎界面T细胞功能研究进展

母-胎界面免疫耐受是成功妊娠建立和维持的基础,T细胞是子宫蜕膜免疫细胞的重要组成细胞,既要介导抗感染免疫,保护胚胎免遭外来病原体攻击,同时又要参与母体接受同种异体胚胎的复杂免疫调节过程,在调控胚胎植入和维持妊娠过程中发挥重要作用,其功能失调可能会导致早期妊娠失败或中晚期妊娠并发症。本文就近年来关于妊娠期母-胎界面T细胞亚群的组成、表型特征及其功能进行介绍,并进一步阐述蜕膜CD4⁺与CD8⁺T细胞在母-胎免疫调节中的作用,以及异常调控致早期妊娠失败的分子机制,有助于深入理解母-胎免疫耐受机制,为妊娠相关疾病的防治提供新的线索。     

母胎界面免疫微环境在分娩启动和早产发生中的作用和机制

人类妊娠维持和分娩启动,与母胎界面免疫微环境的动态平衡密切相关。妊娠早期,母胎界面丰富的血供和免疫细胞相互作用营造的免疫耐受微环境是胚胎着床的关键;临近分娩时,原位或招募的免疫细胞在母胎界面局部形成炎性反应环境,促使胎儿从母体排出。因此,母胎界面免疫微环境调控着妊娠和分娩的各个环节,其平衡紊乱或异常会导致流产或早产的发生。本文就母胎界面几种重要的免疫细胞在分娩启动及早产发生中的作用和机制加以综述。     

主要组织相容性抗原的研究进展

主要上容性抗原是一种分布在细胞表面，并具种系特异性的抗原蛋白，用以将细胞内加工过程的肽段提呈到细胞表面，以激活免疫细胞，在移植器官的排斥反应、抗感染抗肿瘤当中起重要作用     

滋养层细胞表面主要组织相容性复合体抗原的研究进展

胎盘滋养层是直接与母体接触的与母体基因型不同的胎儿组织，滋养层细胞是否表达主要组织相容性复合体(MHC)抗原以及表达何种MHC抗原对于妊娠成功与否至关重要.非经典MHCⅠ类抗原发现较晚，其中HLA-G在滋养层细胞表达，可以保护带有父方同种异体抗原的胎儿免受母体免疫系统的杀伤.经典MHCⅠ类抗原有多种亚型，不同亚型在滋养层细胞的表达有所不同.MHCⅡ类抗原在妊娠维持过程中表达极弱，新近的研究资料表明，滋养层细胞CⅡTA在MHCⅡ类基因表达调控中起主要作用.     

病毒干扰MHCⅠ类抗原呈递策略的研究进展

细胞表面MHCⅠ类分子在CTL的产生和作为CTL受体的配体清除病毒感染细胞中发挥着重要作用。因此,许多病毒在其生活周期的不同阶段干扰MHCⅠ类抗原呈递并不足为奇。深入理解病毒利用的干扰策略不仅有助于揭示病毒的致病机理,而且有助于制定新的对策避免病毒逃逸,这些研究最终可能建立有效控制病毒感染的免疫疗法。因此,本文将就病毒干扰MHCⅠ类抗原呈递策略的研究进展做一综述。     

炭疽杆菌保护性抗原(PA)重组腺病毒的构建及免疫效果分析

探讨利用腺病毒载体作为炭疽杆菌基因工程疫苗载体的可行性.从载体pcDNA3.1-PA上PCR扩增PA片断,将该片断克隆入质粒pAdTrack-CMV,得到阳性克隆pAdTrack-PA.PmeI线性化的阳性克隆转化含有腺病毒骨架质粒pAdeasy-1的BJ5183感受态细胞,经同源重组后得到重组腺病毒vAd-PA.vAd-PA经PacI线性化后,脂质体介导转染293细胞,经Western- blot检测表明PA在293细胞中得到表达.重组病毒肌肉注射免疫BALB/c小鼠,用ELISA方法检测血清中产生了特异性抗体,抗体滴度计算几何均数为12800.该研究为进一步研究以腺病毒为活载体的疫苗奠定了基础.     

人胎肝中肝细胞生长因子poly(A)~ mRNA在非洲爪蟾卵母细胞内的翻译

采用SDS/氯仿/苯酚法和oligo(dT)纤维素亲和层析从人胎肝提取poly(A)~ mRNA,注入非洲爪蟾卵母细胞,翻译出肝细胞生长因子(HGF),产物能从卵母细胞中分泌。在9种细胞(包括人与小鼠的4种不同组织和5种细胞系)检测系统中,证明翻译的HGF与直接提取的HGF活性一致,应用滤膜超滤法估计分子量均在10～30kDa,可以初步认为两者是同一物质。从而,支持了人胎肝HGF是胎儿肝脏细胞基因表达的产物。     

主要组织相容性复合体(MHC)基因的研究概况

主要组织相容性复合体(MHC)因其在免疫方面的重要作用而倍受免疫学家重视．随着研究的不断深入,了解到MHC是一个高度多态的基因群,它广泛分布于各种脊椎动物体内．MHC除了具有免疫功能外,还在其它许多方面起作用．MHC基因的多态性是最受关注的特征,尤其是Ⅱ类基因．根据MHC基因的多态性,可以在遗传、进化、行为、保护及生态等许多方面对其进行研究．就目前的研究情况,在结构、功能及应用等方面对MHC作了介绍．     

MHC (Major Histocompatibility Complex)-DRB Genes and Polymorphisms in Common Marmoset

A New World monkey, the common marmoset (Callithrix jacchus), will be used as a preclinical animal model to study the feasibility of cell and gene therapy targeting immunological and hematological disorders. For elucidating the immunogenetic background of common marmoset to further studies, in the present study, polymorphisms of MHC-DRB genes in this species were examined. Twenty-one Caja-DRB exon 2 alleles, including seven new ones, were detected by means of subcloning and the polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) methods followed by nucleotide sequencing. Based on the alignment of these allele sequences, we designed two pairs of specific primers and established a PCR-SSCP method for DNA-based histocompatibility typing of the common marmoset. According to the family segregation data and phylogenetic analyses, we presumed that Caja-DRB alleles could be classified into five different loci. Southern blotting analysis also supported the existence of multiple DRB loci. The patterns of nucleotide substitutions suggests that positive selection operates in the antigen-recognition sites of Caja-DRB genes. Received: 18 February 2000 / Accepted: 17 May 2000     

Disruption of Multivesicular Body Vesicles Does Not Affect Major Histocompatibility Complex (MHC) Class II-Peptide Complex Formation and Antigen Presentation by Dendritic Cells

The antigen processing compartments in antigen-presenting cells (APCs) have well known characteristics of multivesicular bodies (MVBs). However, the importance of MVB integrity to APC function remains unknown. In this study, we have altered the ultrastructure of the MVB by perturbing cholesterol content genetically through the use of a deletion of the lipid transporter Niemann-Pick type C1 (NPC1). Immunofluorescence and electron microscopic analyses reveal that the antigen processing compartments in NPC1^−/− dendritic cells (DCs) have an abnormal ultrastructure in that the organelles are enlarged and the intraluminal vesicles are almost completely absent and those remaining are completely disorganized. MHC-II is restricted to the limiting membrane of these enlarged MVBs where it colocalizes with the peptide editor H2-DM. Curiously, proteolytic removal of the chaperone protein Invariant chain from MHC-II, degradation of internalized foreign antigens, and antigenic-peptide binding to nascent MHC-II are normal in NPC1^−/− DCs. Antigen-pulsed NPC1^−/− DCs are able to effectively activate antigen-specific CD4 T cells in vitro, and immunization of NPC1^−/− mice reveals surprisingly normal CD4 T cell activation in vivo. Our data thus reveal that the localization of MHC-II on the intraluminal vesicles of multivesicular antigen processing compartments is not required for efficient antigen presentation by DCs.     

小鼠组织相容性抗原的提取与纯化

以建立方便、大量纯化组织相容性抗原的方法为目的。用０．５％Ｔｒｉｔｏｎ／Ｔｒｉｓ抽提小鼠组织相容性抗原（Ｈ－２）抗原,利用抗Ｈ－２抗原抗体制备的亲和柱,特异性结合Ｈ－２抗原,再用０．５％ＤＯＣ、０．６５ＭＮａＣｌ洗脱结合Ｈ－２抗原。结果显示：电泳显示纯化物为４５ｋｄ（重链）,１２ｋｄ（轻链）两条带,纯化物具有明显的血清学及生物学活性;这种亲和层析法可大量纯化组织相容性抗原,用于器官移植研究及组织相容性抗原的免疫功能研究。     

Red Queen Processes Drive Positive Selection on Major Histocompatibility Complex (MHC) Genes

Major Histocompatibility Complex (MHC) genes code for proteins involved in the incitation of the adaptive immune response in vertebrates, which is achieved through binding oligopeptides (antigens) of pathogenic origin. Across vertebrate species, substitutions of amino acids at sites responsible for the specificity of antigen binding (ABS) are positively selected. This is attributed to pathogen-driven balancing selection, which is also thought to maintain the high polymorphism of MHC genes, and to cause the sharing of allelic lineages between species. However, the nature of this selection remains controversial. We used individual-based computer simulations to investigate the roles of two phenomena capable of maintaining MHC polymorphism: heterozygote advantage and host-pathogen arms race (Red Queen process). Our simulations revealed that levels of MHC polymorphism were high and driven mostly by the Red Queen process at a high pathogen mutation rate, but were low and driven mostly by heterozygote advantage when the pathogen mutation rate was low. We found that novel mutations at ABSs are strongly favored by the Red Queen process, but not by heterozygote advantage, regardless of the pathogen mutation rate. However, while the strong advantage of novel alleles increased the allele turnover rate, under a high pathogen mutation rate, allelic lineages persisted for a comparable length of time under Red Queen and under heterozygote advantage. Thus, when pathogens evolve quickly, the Red Queen is capable of explaining both positive selection and long coalescence times, but the tension between the novel allele advantage and persistence of alleles deserves further investigation.     

Differential Transmembrane Domain GXXXG Motif Pairing Impacts Major Histocompatibility Complex (MHC) Class II Structure

Major histocompatibility complex (MHC) class II molecules exhibit conformational heterogeneity, which influences their ability to stimulate CD4 T cells and drive immune responses. Previous studies suggest a role for the transmembrane domain of the class II αβ heterodimer in determining molecular structure and function. Our previous studies identified an MHC class II conformer that is marked by the Ia.2 epitope. These Ia.2⁺ class II conformers are lipid raft-associated and able to drive both tyrosine kinase signaling and efficient antigen presentation to CD4 T cells. Here, we establish that the Ia.2⁺ I-A^k conformer is formed early in the class II biosynthetic pathway and that differential pairing of highly conserved transmembrane domain GXXXG dimerization motifs is responsible for formation of Ia.2⁺ versus Ia.2⁻ I-A^k class II conformers and controlling lipid raft partitioning. These findings provide a molecular explanation for the formation of two distinct MHC class II conformers that differ in their inherent ability to signal and drive robust T cell activation, providing new insight into the role of MHC class II in regulating antigen-presenting cell-T cell interactions critical to the initiation and control of multiple aspects of the immune response.     

Assembly and Function of the Major Histocompatibility Complex (MHC) I Peptide-loading Complex Are Conserved Across Higher Vertebrates

Antigen presentation to cytotoxic T lymphocytes via major histocompatibility complex class I (MHC I) molecules depends on the heterodimeric transporter associated with antigen processing (TAP). For efficient antigen supply to MHC I molecules in the ER, TAP assembles a macromolecular peptide-loading complex (PLC) by recruiting tapasin. In evolution, TAP appeared together with effector cells of adaptive immunity at the transition from jawless to jawed vertebrates and diversified further within the jawed vertebrates. Here, we compared TAP function and interaction with tapasin of a range of species within two classes of jawed vertebrates. We found that avian and mammalian TAP1 and TAP2 form heterodimeric complexes across taxa. Moreover, the extra N-terminal domain TMD0 of mammalian TAP1 and TAP2 as well as avian TAP2 recruits tapasin. Strikingly, however, only TAP1 and TAP2 from the same taxon can form a functional heterodimeric translocation complex. These data demonstrate that the dimerization interface between TAP1 and TAP2 and the tapasin docking sites for PLC assembly are conserved in evolution, whereas elements of antigen translocation diverged later in evolution and are thus taxon specific.     

Pseudomonas aeruginosa Cif Protein Enhances the Ubiquitination and Proteasomal Degradation of the Transporter Associated with Antigen Processing (TAP) and Reduces Major Histocompatibility Complex (MHC) Class I Antigen Presentation

Cif (PA2934), a bacterial virulence factor secreted in outer membrane vesicles by Pseudomonas aeruginosa, increases the ubiquitination and lysosomal degradation of some, but not all, plasma membrane ATP-binding cassette transporters (ABC), including the cystic fibrosis transmembrane conductance regulator and P-glycoprotein. The goal of this study was to determine whether Cif enhances the ubiquitination and degradation of the transporter associated with antigen processing (TAP1 and TAP2), members of the ABC transporter family that play an essential role in antigen presentation and intracellular pathogen clearance. Cif selectively increased the amount of ubiquitinated TAP1 and increased its degradation in the proteasome of human airway epithelial cells. This effect of Cif was mediated by reducing USP10 deubiquitinating activity, resulting in increased polyubiquitination and proteasomal degradation of TAP1. The reduction in TAP1 abundance decreased peptide antigen translocation into the endoplasmic reticulum, an effect that resulted in reduced antigen available to MHC class I molecules for presentation at the plasma membrane of airway epithelial cells and recognition by CD8⁺ T cells. Cif is the first bacterial factor identified that inhibits TAP function and MHC class I antigen presentation.