Processing of a minimal antigenic peptide alters its interaction with MHC molecules

Before their recognition by T lymphocytes, protein antigens generally require processing by antigen-presenting cells. In a poorly understood series of events, the protein antigen is internalized, transformed and re-expressed on the surface of the antigen-presenting cell in association with gene products of the major histocompatibility complex (MHC). Small peptides derived from the native protein can be recognized in the absence of antigen processing, suggesting that processing involves proteolytic degradation. These peptides are thought to mimic the naturally produced peptide fragment. We describe here a synthetic peptide antigen of this type which does not require processing but which is nevertheless further processed by splenic antigen-presenting cells. Interestingly, this processing event specifically alters the interaction of the peptide with the class II MHC (Ia) molecule, markedly affecting both its potency as an antigen in vitro and its immunogenicity in vivo (IR gene control).     

Enhancement of polyoma virus middle T antigen tyrosine phosphorylation by epidermal growth factor

Polyoma virus codes for three proteins involved in host cell transformation: the large, middle and small T antigens. Middle T antigen is a major transforming protein which is responsible for the induction of the phenotype of transformed cells and, without it, transformation does not occur (reviewed in refs 1-4). Middle T antigen alone can transform established cell lines, although large, and possibly small, T antigens are also required for the full expression of the phenotype of transformed cells in media with a low concentration of serum. A subfraction of middle T antigen is associated with a protein kinase activity which phosphorylates middle T antigen in vitro on tyrosine. There is a strong correlation between the level of this kinase activity and the degree of expression of the phenotype of transformed cells. We report here that epidermal growth factor (EGF) stimulates tyrosine phosphorylation of middle T antigen, suggesting the possibility that mitogenic growth factor(s) regulates this phosphorylation activity.     

Defective processing and presentation of exogenous antigens in mutants with normal HLA class II genes

Presentation of an exogenous protein antigen to helper (CD4+)T-lymphocytes by antigen presenting cells (APC) generally requires that the APCs degrade the native protein antigen into an immunogenic peptide, a process termed 'antigen processing', and that this peptide bind to a major histocompatibility complex (MHC) class II molecule. The complex of peptide and MHC molecule on the APC surface provides the stimulatory ligand for the alpha beta T cell receptor. The intracellular pathways and molecular mechanisms involved in the generation of the peptide-MHC complex are not well understood. Here, we describe several mutant APCs which are altered in their ability to present native exogenous protein antigens but effectively present immunogenic peptides derived from these proteins. The lesions in these mutants are not in the class II structural genes, but they affect the conformation of mature class II dimers.     

An embryo protein induced by SV40 virus transformation of mouse cells

A specific protein of molecular weight (MW) approximately 55,000 (55K) was found recently by immunoprecipitation in all SV40 virus-transformed mammalian cells, in addition to the SV40 large T antigen (appoximately 94K) and small antigen (approximately 17K), which are the only proteins coded by the 'early half' of the SV40 genome. The 55K protein is encoded by cellular DNA; its peptide pattern is different from that of the SV40 antigens and it is species specific in mouse, rat, hamster, monkey and human SV40-transformed (or infected) cells. A 55K protein with a similar peptide pattern was found in mouse embryonal carcinoma cells not exposed to SV40. Similar proteins were reported in mouse sarcomas and leukaemias induced by a great variety of aetiological agents and also in a spontaneously transformed mouse fibroblast cell line, and it has been suggested that the protein may be a general correlated of cellular tumorigenicity. We now report that the approximately 55K protein is present in primary cell cultures from 12-14 day old mouse embryos, but not in 16-day old mouse embryos. The embryo protein has a peptide pattern virtually indistinguishable from that of the SV40-induced protein. We also show by comparing closely related cell families that spontaneously transformed highly tumorigenic mouse cells do not possess the 55K protein.     

Tissue localization and chromosomal assignment of a serum protein that tracks the cystic fibrosis gene

The basic gene defect in the autosomal recessive disorder cystic fibrosis has not been identified, and no firm linkage of the disorder to any other marker has been reported. However, a serum protein abnormality present in unaffected heterozygotes as well as in affected homozygotes has been described, and immunological quantitation of this protein, termed cystic fibrosis antigen, allows the three genotypes to be distinguished. We show here that an immunologically indistinguishable protein is present at high concentrations in granulocytes from normal and cystic fibrosis individuals as well as in myeloid leukaemia cells. Somatic cell hybrids between the mouse myeloid stem-cell line WEHI-TG and myeloid leukaemia cells express cystic fibrosis antigen only when human chromosome I is present.     

p53 and DNA polymerase alpha compete for binding to SV40 T antigen

The large T antigen (T) of simian virus 40 is a multifunctional protein required for both viral DNA replication and cellular transformation. T antigen forms specific protein complexes with the host protein p53 in both virus-infected and transformed cells. p53 has recently been shown to be an oncogene, but its normal function is not clear. We previously established a radioimmunoassay to study the newly described complex between T antigen and DNA polymerase alpha, and have noted a similarity between the antigenic changes induced in T by the binding of both p53 and polymerase. We now extend this analysis to a larger collection of anti-T antibodies and formally establish that p53 and DNA polymerase alpha can compete for binding to the SV40 T antigen. At a critical concentration of the three components it is possible to detect a trimeric complex of T, p53 and DNA polymerase alpha. Our observations have important implications for the control by these nuclear oncogenes of viral and cellular DNA synthesis and viral host range in both normal and transformed cells. We present a model for the action of p53 in growth control.     

吗啡人工抗原的合成及多克隆抗体的制备

利用化学法合成吗啡人工抗原,将此抗原免疫新西兰大白兔制备抗吗啡多克隆抗体.利用混合酸酐法将吗啡人工抗原分别与蛋白质载体BSA及OVA偶联,经蛋白质电泳以及紫外扫描检测,证明吗啡人工抗原合成成功.用间酶联免疫检测法检测,证明制备得到了高效价的吗啡多克隆抗体血清,且与吗啡人工抗原具有高特异性反应,可用于吗啡免疫学检测方法的研究.     

Non-tolerance and autoantibodies to a transgenic self antigen expressed in pancreatic beta cells

Transgenic mice expressing simian virus 40 T antigen under control of the insulin gene regulatory region vary in their response to this protein. Each lineage is characteristically either tolerant to T antigen, or not, in which case autoantibodies arise with high frequency, and lymphocytes infiltrate and disrupt the pancreatic islets. Both non-tolerance and the autoimmune response appear to result from delayed onset of T antigen expression during beta cell development.     

Stimulation of p21ras upon T-cell activation

External signals that control the activity of proteins encoded by the ras proto-oncogenes have not previously been characterized. It is now shown that stimulation of the antigen receptor of T lymphocytes causes a rapid activation of p21ras. The mechanism seems to involve a decrease in the activity of GAP, the GTPase-activating protein, on stimulation of protein kinase C. In lymphocytes, p21ras may therefore be an important mediator of the action of protein kinase C.     

牛角膜上皮45.4 kd水溶性蛋白质在脊椎动物角膜中特异性表达的免疫组化研究

用SDS 聚丙烯酰胺凝胶电泳的方法 ,制备了 45 4kd的水溶性牛角膜上皮特异性蛋白质 ,免疫家兔得到其抗体 .利用免疫组化方法研究了此蛋白质在脊椎动物角膜中表达的普遍性 .结果表明 ,此水溶性蛋白质在小白鼠、豚鼠、家兔、羊等哺乳动物和以鳖为代表的爬行动物角膜上皮细胞中呈阳性反应 ,而在鲤鱼、热带鱼、花背蟾蜍、鸡、北京雨燕等其他脊椎动物角膜中呈阴性反应     

Human gamma delta+ T cells respond to mycobacterial heat-shock protein

Most T cells recognize antigen through the T-cell antigen receptor (TCR)alpha beta-CD3 complex on the T-cell surface. A small percentage of T cells, however, do not express alpha beta but a second type of TCR complex designated gamma delta (ref. 2). Unlike alpha beta+ lymphocytes, gamma delta+ lymphocytes do not generally express CD4 or CD8 molecules, and the nature of antigen recognition by these cells is unknown. To study antigen recognition by gamma delta+ lymphocytes we raised a gamma delta+ alpha beta- -CD4-CD8- line from an individual immune to PPD (purified protein derivative). This line showed a specific proliferative response to PPD and to a recombinant mycobacterial heat-shock protein (HSP) of relative molecular mass 65,000 (65K). The gamma delta+ line was shown to exhibit a major response to HSP in the presence of autologous antigen-presenting cells (APCs). Minor responses occurred, however, with APCs matched for some HLA class I or II antigens, whereas no response occurred with HLA-mismatched APCs. These findings, therefore, document the requirement of HSP-reactive gamma delta+ lymphocytes for histocompatible APCs.     

与细胞增殖相关的核仁杭原

用自制的抗核仁抗原的抗血清对其相应的核仁抗原(NAg-1)进行了研究.间接免疫荧光染色及细胞化学分析表明,NAg-1,可能是一种与DNA结合并与rDNA合成有关的酸性蛋白质.其在静止的人淋巴细胞和人正常非增殖组织中基本不表达或仅有微量表达,在人癌细胞和人正常增殖细胞中表达.并具有一定的种属特异性.NAg-1在快速增殖的HL-60细胞中表达的百分比大大高于缓慢增殖的细胞.随着HL-60细胞的密度增大,其细胞核仁抗原表达的百分比大大下降,说明NAg-1与细胞的增殖相关.     

T-cell-mediated association of peptide antigen and major histocompatibility complex protein detected by energy transfer in an evanescent wave-field

Helper T cells recognize foreign antigen displayed on antigenpresenting cells which also express self-molecules of the major histocompatibility complex (MHC). A single T-cell receptor mediates recognition of both MHC and foreign antigen. A proposed ternary complex between T-cell receptor, foreign antigen and MHC antigen has not yet been demonstrated (see ref. 1 for review). Here, we show that a fluorescein-labelled synthetic peptide, together with Texas red-labelled class II MHC antigen, I-Ad, stimulates the production of interleukin-2 by a peptide-specific I-Ad-restricted T-cell hybridoma when reconstituted in a lipid membrane on a glass substrate. Under the same conditions, resonance-energy transfer from donor peptide to acceptor I-A can be stimulated in an evanescent wave-field only in the presence of the specific T-hybrid. Our results show that the T cell stabilizes an association between peptide antigen and class II MHC protein to within a distance of about 40 A.     

Phosphorylation of large tumour antigen by cdc2 stimulates SV40 DNA replication

Simian virus 40 large tumour antigen (T) is a replication origin binding protein required for viral DNA synthesis. Unphosphorylated T antigen is deficient in promoting DNA replication in vitro but can be activated by phosphorylation at residue threonine 124 by the cdc2 protein kinase. This observation demonstrates that T is regulated by phosphorylation and provides a model for cdc2 function in the control of DNA replication.     

Induction of regulatory T-lymphocyte responses by liposomes carrying major histocompatibility complex molecules and foreign antigen

Regulatory (helper and suppressor) T lymphocytes become activated only when foreign antigen is presented to them on the surface of antigen-presenting cells (APC), together with class II major histocompatibility complex (MHC) molecules (heterodimers of polypeptides of 28,000 and 35,000 relative molecular mass). Once activated by a certain foreign antigen--MHC combination, T cells react to the same antigen only in combination with the same MHC molecule, a phenomenon termed MHC restriction of T-cell recognition (reviewed in refs 1,5). Studies of the mechanisms involved in antigen presentation and MHC restriction have been hampered mainly by the virtual impossibility of inducing T-cell responses in the absence of APC. We describe here the production of synthetic lipid vesicles with inserted class II MHC molecules and a protein antigen coupled covalently to the lipid. These liposomes are shown to stimulate cloned helper T cells and T-cell hybridomas in an antigen-specific, MHC-restricted manner in the absence of APC. Thus, the recognition of foreign antigen together with class II MHC molecules seems to be the only signal required for the activation of antigen-primed regulatory T cells. Furthermore, 'processing' of antigen by APC is not essential for its recognition by T cells.     

腐食酪螨和粉尘螨的共同抗原

目的：探讨腐食酪螨和粉尘螨之间是否存在共同抗原.方法：对粉螨过敏患者进行腐食酪螨和粉尘螨特异性IgE相关性分析，用SDS-PAGE分析腐食酪螨和粉尘螨变应原，并对螨特异性IgE阳性血清进行免疫印迹试验及抑制试验.结果：42例粉螨过敏患者血清粉尘螨和腐食酪螨特异性IgE光密度值相关性较高（r=0.641 5，P＜0.01）.SDS-PAGE分析知腐食酪螨和粉尘螨变应原分子量均为10 kD～110 kD.免疫印迹抑制试验表明，腐食酪螨变应原可与粉尘螨变应原发生交叉反应.结论：腐食酪螨和粉尘螨间存在共同抗原.     

Cloning and expression in E. coli of the malarial sporozoite surface antigen gene from Plasmodium knowlesi

The malarial sporozoite, the infective stage found in the salivary gland of the insect vector, bears highly immunogenic surface antigen(s). Repeated exposure to irradiated sporozoites induces protection against malaria in several host species, including man. Further, monoclonal antibodies that confer passive immunity react with the immunogenic surface determinants of different sporozoite species. One approach to prevent malaria, therefore, would be to produce a vaccine that induces high titres of circulating antibodies against the sporozoite surface determinant(s). However, production of such a vaccine has not been possible since sporozoites cannot be cultivated in vitro and, therefore, only limited amounts of surface antigen may be obtained. To overcome this problem, we have prepared mRNA from Plasmodium knowlesi-infected mosquitoes to construct a cDNA library. From this library we have isolated a clone that expresses the sporozoite surface antigen as a beta-lactamase fusion protein in the plasmid pBR322. This is the first potentially protective malarial antigen to be cloned by recombinant DNA technology.