T细胞相关趋化因子及受体的研究进展

T细胞在发育、成熟、活化及发挥生物学效应的各个阶段表达不同的趋化因子受体。T细胞相关趋化因子及其受体的表达在不同的细胞类群上具有时相和分布的差异,并通过趋化因子与其受体特异性结合的模式,参与T细胞的发育过程,调控细胞的定向迁移,从而影响局部甚至整个机体的免疫状态。此外,它还在炎症、感染、肿瘤、自身免疫疾病等众多病理生理的过程中发挥重要作用。在这一领域的深入研究将为相关疾病的预防和治疗提供新的思路和途径。     

The chemokine SLC is expressed in T cell areas of lymph nodes and mucosal lymphoid tissues and attracts activated T cells via CCR7

Secondary lymphoid-tissue chemokine, SLC, also known as exodus-2 and 6Ckine, is a novel CC chemokine with selectivity for T lymphocytes and preferential expression in lymphoid tissues. We have studied its production, receptor usage and biological activities. High levels of SLC mRNA were detected in lymph nodes, the gastrointestinal tract and several gland tissues, but no expression was found by Northern blot analysis in freshly isolated or stimulated blood monocytes and lymphocytes, or neutrophils and eosinophils. In situ hybridization revealed constitutive expression of SLC in the T cell areas and the marginal zone of follicles in lymph nodes and the mucosa-associated lymphoid tissue, but not in B cell areas or sinuses. Comparison with immunocytochemical staining showed similarity between the in situ expression of SLC and the distribution of interdigitating dendritic cells but not with sinus-lining dendritic cells, macrophages or T lymphocytes. SLC induced chemotaxis of T lymphocytes and its activity increased considerably when the cells were conditioned with IL-2 or phytohemagglutinin (PHA). Under optimal conditions SLC had unusually high efficacy and induced the migration of up to 50 % of input T lymphocytes. SLC also induced Ca²⁺ mobilization in these cells. Similar responses were obtained with EBI1 ligand chemokine (ELC), and sequential stimulation with both chemokines led to cross-desensitization, suggesting that SLC acts via the ELC receptor, CCR7. This was confirmed using murine pre-B cells stably transfected with CCR7 which bound SLC with high affinity and showed chemotaxis and Ca²⁺ mobilization in response to both SLC and ELC. In T lymphocytes PHA and IL-2, which enhanced chemotactic responsiveness, also markedly enhanced CCR7 expression. In contrast to all known chemokine receptors, up-regulation of CCR7 by IL-2 was transient. A maximum was reached in 2 – 3 days and expression returned to initial levels within 8 – 10 days. The present study shows that SLC is constitutively produced within the T cell areas of secondary lymphoid organs and attracts T lymphocytes via CCR7.     

Increased expression of complement receptor type 1 (CR1, CD35) on human peripheral blood T lymphocytes after polyclonal activation in vitro

The receptor for C3b and C4b—complement receptor type 1 (CR1, CD35)—is present on a variety of cell types including erythrocytes, phagocytic cells, B lymphocytes and a small sub-population of T lymphocytes. The function of the receptor varies according to the different cell types, but a T lymphocytes the function is as yet not known. The present study concerns the influence of polyclonal stimulation on CR1-expressing T lymphocytes. Incubation with PHA resulted in a dose-dependent increase in the number of CR1-positive T lymphocytes. The CR1-expression T lymphocytes were found in both the CD4- and the CD8-positive subpopulation, but a significant stimulatory increase was only found in the CD4-positive population. A significant increase in the number of CR1-expressing T lymphocytes was found when monocytes were present during stimulation, indicating an importance of monocytes and/or monocyte products. However, the increase was not regulated by arachidonic acid metabolites of the cyclo-oxygenase pathway as indomethacin failed to inhibit the increase. Neither did rIL-Iα, rIL-1β, rTNFα nor rIL-6 alter the number of CR1-expressing T lymphocytes. The results of this study indicate a role for CR1 on T lymphocytes in the regulation of the immune system.     

Molecular cloning, tissue expression, and chromosomal assignment of a novel gene encoding a subunit of the human signal-recognition particle

Human cancers derived from breast, esophageal, or ovarian tissues frequently show allelic losses on chromosome band 17q25. Moreover, a locus responsible for hereditary focal nonepidermolytic palmoplantar keratoderma, a condition associated with esophageal cancer (TOC; tylosis with oesophageal cancer), has been mapped to the same band. During efforts to sequence, by shotgun methods, a 1-Mb target region that we had defined as the DNA segment harboring the putative tumor suppressor gene(s) involved in these events, we identified a novel cDNA. The full-length cDNA is 2495 bp long and is expressed predominantly in skeletal muscle, heart, kidney, and placenta. The predicted product, a 627-amino-acid protein, exhibited significant sequence homology to the canine 68-kd subunit of the signal recognition particle that has been implicated in the transport of secreted and membrane proteins to the endoplasmic reticulum for proper processing. We confirmed the location of this gene at chromosome 17q25.1 by radiation-hybrid mapping and by fluorescence in situ hybridization. Received: September 18, 2000 / Accepted: November 10, 2000     

Molecular cloning of a cDNA encoding the human interleukin 4 receptor

Using the mouse interleukin 4 (IL-4) receptor cDNA as a probe, we isolated a cDNA encoding the human IL-4 receptor (hIL-4 receptor) from a multifactor-responsive human myeloid cell line, TF1. The cDNA encodes for an open reading frame of 825 amino acids including a signal sequence (25 amino acids), the external domain (207 amino acids), a transmembrane domain (24 amino acids), and a large cytoplasmic domain (569 amino acids). The human IL-4 receptor has a 65% identity with the mouse IL-4 receptor at the nucleic acid level and retains the typical structural motif of the previously described cytokine receptor family. COS7 cells transfected with the full-length cDNA expressed high levels (140,000 sites/cell) of IL-4 binding sites, with a Kd = 80 pM, an affinity identical to that of the original TF1 cells. Similar to IL-4 responsive cells, cross-linking of [125I]IL-4 to COS7 cells transfected with the cDNA showed a major protein of 130-150 kd and minor species of 55-85 kd.     

Antibody-mediated delivery of antigen to chemokine receptors on antigen-presenting cells results in enhanced CD4+ T cell responses

Here, we have investigated if targeting of T cell epitopes to chemokine receptors results in improved CD4+ T cell responses. Mouse monoclonal antibodies (mAb) with kappaL chains were targeted to various chemokine receptors expressed on human monocytes or immature dendritic cells (DC), and proliferation of cloned human, DR4-restricted CD4+ T cells specific for mouse Ckappa(40-48) was measured. When using monocytes as antigen-presenting cells, mAb specific for CCR1, CCR2, CCR5, and CXCR4 were 100-10,000-fold more efficient at inducing T cell proliferation when compared to isotype-matched control mAb on a per molecule basis. Targeting of immature DC was less effective and was only seen with anti-CCR1 and anti-CXCR4 mAb. Anti-chemokine receptors mAb required to be processed by the conventional endosomal MHC class II presentation pathway. The mAb did not induce signaling through the chemokine receptors as they failed to induce mobilization of cytosolic Ca2+ and actin polymerization. They also failed to induce APC maturation. The results strongly suggest that chemokine receptors channel antigen into the endocytic pathway for presentation on MHC class II molecules. Targeting T cell epitopes to chemokine receptors by recombinant antibody should be a useful vaccine strategy for the induction of strong CD4+ T cell responses.     

Site-directed mutagenesis of the chemokine receptor CXCR6 suggests a novel paradigm for interactions with the ligand CXCL16

Chemokine receptor CXCR6 mediates the chemotaxis and adhesion of leukocytes to soluble and membrane-anchored forms of CXCL16, and is an HIV-1 co-receptor. Here, we describe the effects of mutation of acidic extracellular CXCR6 residues on receptor function. Although most CXCR6 mutants examined were expressed at levels similar to wild-type (WT) CXCR6, an N-terminal E3Q mutant was poorly expressed, which may explain previously reported protective effects of a similar single nucleotide polymorphism, with respect to late-stage HIV-1 infection. In contrast to several other chemokine receptors, mutation of the CXCR6 N terminus and inhibition of post-translational modifications of this region were without effect on receptor function. Likewise, N-terminal extension of CXCL16 resulted in a protein with decent potency and efficacy in chemotaxis and not, as anticipated, a CXCR6 antagonist. D176N and E274Q CXCR6 mutants were unable to interact with soluble CXCL16, suggesting a critical role for D176 and E274 in ligand binding. Intriguingly, although unable to interact with soluble CXCL16, the E274Q mutant could promote robust adhesion to membrane-anchored CXCL16, suggesting that soluble and membrane-bound forms of CXCL16 possess distinct conformations. Collectively, our data suggest a novel paradigm for the CXCR6:CXCL16 interaction, a finding which may impact the discovery of small-molecule antagonists of CXCR6.     

Molecular cloning of cDNAs encoding a LD78 receptor and putative leukocyte chemotactic peptide receptors

Several cDNA clones encoding receptors for leukocyte chemoattractants,including IL-8, C5a, N-formyl peptides (FP), and platelet-activatingfactor, have been isolated in the past 3 years. The primarystructure of these receptors revealed that they are membersof the superfamily of G protein-coupled receptors containingseven transmembrane domains. In this study the polymerase chainreaction was carried out to isolate novel cDNA clones encodinghuman receptors of IL-8 related cytokines, chemokines, froma human monocyte cDNA library using degenerate oligonucleotideprimers devised from conserved sequences among the cDNAs encodingthe human receptors for IL-8, FP and C5a. Four novel cDNA clones(HM63, HM74, HM89, and HM145) in addition to cDNAs for FP andC5a receptors were isolated. All polypeptides encoded by thecloned cDNAs share common features with the G protein-coupledreceptor superfamlly, such as seven putative hydrophobic transmembranedomains and, except for HM74, N-linked glycosylation sites nearthe N-termlnus. The amino acid sequence identities among HM63,HM89, HM145, IL-8 receptors, FP receptor, and C5a receptor arein the range of 24-68%, higher than those of other members ofthe G protein-coupled receptor superfamily. Moreover, the numberof amino acids between the fifth and sixth transmembrane domains,which varies within this superfamily, is the same in these receptors.Thus, three of the newly identified proteins probably belongto a ‘leukocyte chemotactic peptide receptor family’.HM74 differs from the other clones with respect to the aminoacid homology, suggesting that this may be the receptor fora different type of ligand. Furthermore, it was confirmed thatHM145 Is a functional receptor for LD78, one of the C-C chemokines,as revealed by the measurement of decrease of cAMP accumulationas well as calcium influx using stable transfectants.     

Differential expression of chemokine receptors on human IgA+ and IgG+ B cells

Organ-specific lymphocyte homing is dependent on the expression of tissue-specific homing receptors and selected chemokine receptors. During the effector phase of an immune response, IgA and IgG antibody-secreting cells (ASC) are differently distributed in the body. Still, B cell expression of L-selectin and the mucosal homing receptor integrin alpha4beta7 is not related to the isotype produced, but only to the site of antigen encounter. In this study, we examined if differences in chemokine responsiveness between IgA+ and IgG+ B cells could explain their different tissue localization. Circulating CD19+ B cells were isolated and their expression of IgA, IgG, and selected chemokine receptors was determined by flow cytometry. Few Ig+ cells expressed CCR2, CCR3, or CCR9, and there was no difference in the expression of these receptors between IgA+ and IgG+ cells. In contrast, CCR4, CCR5, and CXCR3 was expressed on significantly more IgG+ than IgA+ cells. The function of chemokine receptors on memory B cells and ASC was then tested in the transwell system. IgG+ memory cells migrated to a higher extent than IgA+ cells towards the CXCR3 ligand CXCL11/I-TAC, while there was only a small migration towards the CCR4 ligand CCL17/TARC and the CCR9 ligand CCL25/TECK. ASC migrated poorly to all chemokines tested. In conclusion, this study shows that IgG+ and IgA+ memory B cells have a differential expression of the Th1 associated chemokine receptor CXCR3, as well as of CCR4 and CCR5. In contrast, none of the studied chemokine receptors was preferentially expressed by IgA+ cells.     

Kinetics and expression patterns of chemokine receptors in human CD4+ T lymphocytes primed by myeloid or plasmacytoid dendritic cells

We investigated the kinetics of expression of 12 chemoattractant receptors as a function of cell division following priming of human naive CD4+ T cells by different populations of dendritic cells (DC) and under conditions favoring Th1 or Th2 differentiation. Two chemokine receptors, CXCR3 and CXCR5, were rapidly up-regulated following T cell activation by either monocyte-derived DC, myeloid DC (mDC) or plasmacytoid DC (pDC). While CXCR5 expression was transient, expression of CXCR3 at advanced cell divisions was dependent on differentiation, being expressed at high levels on Th1 cells. Several other receptors (CCR2, CCR3, CCR4, CCR5, CXCR6 and CRTh2) were acquired progressively as a function of cell division and in a fashion that was influenced by polarizing cytokines. The Th2-associated chemoattractant receptors CRTh2 and CCR3 were up-regulated with slower kinetics compared to the Th1-associated receptors CXCR3 and CXCR6, consistent with a different kinetics and efficiency of polarization. Moreover, CCR4 and CXCR6 were preferentially induced in T cells activated by mDC and pDC, respectively. Finally, CXCR5 and CCR7 were also rapidly and transiently up-regulated in memory T cells following TCR stimulation. These results indicate a complex chemokine receptor regulation dependent on both T cell activation and differentiation state. In addition, they reveal the existence of DC-specific cues for the regulation of T cell migratory capacity.     

HIV-1协同受体CXCR4、CCR5及相关趋化因子SDF-1在胎盘的表达

目的：研究HIV-1协同受体CXCR4、CCR5及CXCR4的特异性配体SDF-1在人胎盘组织的表达，探索HIV-1子宫内垂直传播的分子机制。方法：半定量RT-PCR检测早、中、晚孕期胎盘及早孕滋养细胞CXCR4、CCR5 mRNA水平；免疫组化和免疫细胞化学检测早孕胎盘及原代培养滋养细胞CXCR4、CCR5蛋白表达；原位杂交及免疫组化分析SDF-1在早孕胎盘的表达；ELISA测定滋养细胞SDF-1的动态分泌水平。结果：各孕期胎盘表达CXCR4及CCR5 mRNA；CXCR4蛋白定位于滋养细胞，而CCR5蛋白定位于绒毛基质中。滋养细胞可转录并翻译SDF-1，且能分泌可溶性SDF-1。结论：滋养细胞同时表达CXCR4及SDF-1，SDF-1可能通过降调CXCR4而拮抗X4-HIV-1感染胎儿细胞；R5-HIV-1或许能通过滋养层裂隙感染CCR5^#基质细胞和/或Hotbauer细胞，从而发生子宫内垂直传播。     

Molecular cloning,mapping and characterization of a human CK1gamma1 gene

We isolated and sequenced a cDNA clone coding a human protein kinase CK1 (casein kinase 1) by screening a human fetal brain cDNA library. This new cDNA clone of 1756 bp contained an open reading frame, encoding a protein of 438 amino acids with a molecular weight of 50,272 Da and an isoelectric point of 9.37. The entire amino acid sequence of the novel human CK1 was 94% homologous to that of rat CK1gamma1. Northern blot analysis indicated that the human CK1gamma1 was highly expressed in the liver, skeletal muscle, heart and kidney. Furthermore, the human CK1gamma1 gene was mapped to chromosome 15q22 between STS marker D15S159 and D15S125 by polymerase chain reaction analysis of human/rodent hybrid cell panels.     

人早孕蜕膜基质细胞及免疫活性细胞趋化因子受体CXCR6的表达

目的分析人早孕期蜕膜基质细胞趋化因子配基受体对CXCL16/CXCR6的表达及免疫活性细胞趋化因子受体CXCR6的表达,以探讨CXCL16/CXCR6在蜕膜免疫活性细胞募集中的可能规律.方法收集早孕期蜕膜组织,分离蜕膜基质细胞和免疫细胞,分别采用半定量RT-PCR、免疫细胞化学、流式细胞术分析蜕膜基质细胞CXCL16和CXCR6的表达;流式细胞术分析蜕膜CD56^＋CD16^-NK细胞、CD56^＋CD16^＋NK细胞、NKT细胞、T细胞、γδT细胞、单核细胞CXCR6的表达.结果人早孕蜕膜基质细胞高水平转录趋化因子受体CXCR6,低水平转录其配体CXCL16,但CXCL16和CXCR6在蛋白水平的表达偏低.早孕蜕膜γδT细胞CXCR6阳性率为87.29%;CD14^＋单核细胞CXCR6阳性率为47.71%;NKT细胞CXCR6阳性率为44.14%;T细胞CXCR6表达率为32.91%;而蜕膜两种NK细胞（CD56^＋CD16^-、CD56^＋CD16^＋）几乎不表达CXCR6.结论人γδT细胞、单核细胞、NKT细胞、T细胞可能通过表达趋化因子受体CXCR6被募集到蜕膜局部并驻留,从而参与早孕期母胎界面的免疫调节.     

人类胚胎干细胞特异表达新基因HPESCRG1的克隆和特性分析

目的克隆一个人类胚胎干细胞特异表达的新基因并对其特性进行分析。方法从一个在人类胚胎干细胞(embryonicstem,ES)中特异表达的表达序列标签CF948547出发,应用生物信息学方法和分子生物学技术克隆一个新基因,采用逆转录-聚合酶链反应分析新基因的表达谱,并应用增强型绿色荧光蛋白真核表达系统分析新基因的亚细胞定位。结果成功克隆了一个新基因HPESCRG1,GenBank登录号为AY283672。该基因cDNA长1395bp,包含9个外显子和8个内含子,开放阅读框为250～1146bp,定位在3q13.13,预测编码297个氨基酸,预计分子量为33784,等电点为9.35。其编码蛋白有一个SAP功能域,该蛋白定位在细胞核内。该基因仅在人类ES细胞中表达,而在其分化细胞不表达,在人胚胎成纤维细胞、人间充质干细胞、成人和流产胚胎的多种正常组织中不表达。结论HPESCRG1基因是一个人类ES细胞中表达特异性新基因,很可能与人类ES细胞的自我更新和维持其未分化状态密切相关。     

T cell receptor (TCR) Vβ gene usage in bronchoalveolar lavage and peripheral blood T cells from asthmatic and normal subjects

T cells are thought to play an important regulatory role in asthma, but little is known about the T cell repertoire of the human lung or whether asthma is associated with any specific repertoire changes. Flow cytometry and MoAbs to TCR VB (TCRBV) families were used to quantify bronchoalveolar lavage (BAL) and blood T cells from normal and atopic individuals. Clonality was then assessed by polymerase chain reaction (PCR) amplification of cDNA and gene scanning using consensus and family-specific TCRBV primers and confirmed by sequence analysis. In addition, blood and BAL T cell populations were studied pre- and post-allergen challenge in four patients with allergic asthma. The majority of TCRBV families detected in blood by MoAb staining were also represented in BAL. While differences between BAL and blood populations were evident in each individual studied, these differences were not consistent between individuals or between CD4⁺ and CD8⁺ T cell subpopulations. These results are in broad agreement with other published studies, but in contrast to previous work we found a consistent difference between TCRBV7 family usage in blood and BAL in all individuals studied, and a consistently increased proportion of CD4⁺ BAL T cells bearing BV5S2/3 in asthmatics only. After allergen challenge, the pattern of TCRBV gene usage was largely unchanged as judged by flow cytometry. Gene scanning of PCR products generated from consensus VB primers revealed polyclonal lymphocyte populations in blood and BAL from all seven atopic individuals: in one normal tested polyclonal populations were found in blood and oligoclonal populations in BAL. Selected families amplified with family-specific primers BV5S2/3, BV6 and BV7 (chosen because of their predominance in BAL compared with blood) were more variable and revealed predominant polyclonal populations in blood and polyclonal or oligoclonal populations in BAL. In one asthmatic patient a clonal BV5S2 family was found in BAL. Following allergen challenge there were no significant changes in polyclonality/oligoclonality/clonality in three cases, but in one case a clonal BV5S2 population was found after challenge, that had not been evident beforehand. The lung T cell repertoire is thus broadly representative of blood T cells, but shows population differences that may result from response to persistent exposure to airborne antigens common to normal and atopic individuals. Oligoclonal TCRBV family expansion appears to be primarily lung-specific but independent of atopic asthma, although our challenge data in one case support the concept that clonal populations may follow local allergen challenge. These data are consistent with selection and amplification of specific T cell families in the lung in response to local antigenic exposure.