HLA-G研究进展及与肿瘤的相关性

HLA-G属于非经典的HLA-Ⅰ类分子，特异性表达于母胎界面，对于维持人类正常妊娠有重要作用。在肿瘤细胞的异位表达，引起肿瘤细胞逃避宿主免疫监视日益受到重视。本就HLA-G基因结构、多态性、分布、免疫功能等方面的最新研究进展及与肿瘤的相关性作一综述。     

HLA-G结构与功能研究进展

胎盘组织外绒毛滋养层细胞不表达经典的HLAⅠ类分子 ,使这些细胞易感于NK细胞的攻击 ,但由于表达非经典的MHCⅠ类分子HLA G可以防止NK细胞识别这些细胞 ,HLA G至少是 3种NK细胞抑制受体的配体 ;表达HLA G的滋养层细胞可能递呈肽类给T细胞 ,转染膜结合型HLA G1, G2及可溶型HLA G分子的细胞能抑制同种T淋巴细胞的增殖反应及抗原特异性的CTL反应 ;以及HLA G基因的多态性程度是有限的 ,提示HLA G在母体对半异体的胎儿的免疫耐受中可能起一个重要的作用。     

HLA-G研究进展及与肿瘤的相关性

HLA G属于非经典的HLA Ⅰ类分子 ,特异性表达于母胎界面 ,对于维持人类正常妊娠有重要作用。在肿瘤细胞的异位表达 ,引起肿瘤细胞逃避宿主免疫监视日益受到重视。本文就HLA G基因结构、多态性、分布、免疫功能等方面的最新研究进展及与肿瘤的相关性作一综述     

HLA-G与T细胞

人类白细胞抗原G(human leukocyte antigen-G,HLA-G)属于非经典的HLAⅠ类分子,是机体内一种重要的免疫耐受分子。T细胞是细胞免疫的主要效应细胞,在机体维持免疫稳态中发挥重要作用。近来研究发现,HLA-G对T细胞的免疫调节功能一方面依赖于T细胞上抑制性受体直接发挥免疫抑制作用,另一方面通过诱导或胞啃机制产生调节性T细胞(Treg)、HLA-G+T细胞间接参与机体免疫耐受。本文就HLA-G对T细胞调节功能的研究进展作一综述。     

HLA-G与移植免疫研究进展

人类白细胞抗原G(human leucocyte antigen G,HLA-G)是机体内一种重要的免疫耐受分子。HLA-G分子通过直接与免疫细胞上的抑制性受体结合或间接诱导产生HLA-G依赖性调节性细胞,改变细胞因子表达谱,从而调节机体的免疫状态。随着研究的深入,HLA-G分子生物学功能及临床意义从最初的母胎免疫耐受延伸至肿瘤免疫,感染免疫和移植免疫等研究领域。本文就HLA-G在移植免疫中的表达意义及临床应用等相关研究进展作一综述。     

HLA-G在妊娠中的研究进展

人类白细胞抗原G（HLA-G）属于非经典人类主要组织相容性复合体（MHC-Ib）类分子,具有低度多态性和限制性分布的特点,可以通过抑制自然杀伤（NK）细胞、细胞毒性T细胞等效应细胞在妊娠母胎界面免疫中发挥着重要的作用,本文对HLA-G的功能及在试管婴儿和病理妊娠中的研究进展进行了综述。     

可溶性HLA-G1、-G2的原核表达及其蛋白质产物的功能检测

sHLA-G存在于整个妊娠期母胎接触面及母体血循环中,目前被认为是妊娠期一种特异性免疫抑制分子。实验将sHLA-G1、sHLA-G2基因克隆于原核表达载体pET-28a中,转化大肠杆菌BL21(DE3)宿主菌,经IPTG诱导实现目标融合蛋白的高效表达,并通过Ni2+-NTA柱纯化、蛋白质透析梯度复性获得纯化的His-sHLA-G1、His-sHLA-G2融合蛋白。融合蛋白再经凝血酶酶切、苯甲脒琼脂糖凝胶吸附去除6-His标签后,用于体外功能鉴定。结果显示:sHLA-G2与sHLA-G1一样,同样具有抑制T细胞增殖、抑制NK细胞杀伤活性的功能,提示sHLA-G2为一种免疫致耐分子。     

HLA-G分子在体外抑制NK细胞杀伤效应的研究

在获得稳定表达HLA G分子的K5 62细胞克隆的基础上 ,观察 4h及 16h不同效靶比例时NK细胞对靶细胞的杀伤效应 ,结果显示 ,NK细胞对转染HLA G基因的K5 62细胞的杀伤作用较未转染细胞明显降低 (P <0 0 1) ,用W6/ 32及BFL 1单克隆抗体阻断HLA G分子 ,可以恢复NK细胞的杀伤活性。用Y9/Z2 70及XA185 /Z2 70单抗特异性阻断抑制性受体CD94/NKG2A ,未观察到明显影响     

HLA-G诱导T细胞免疫耐受的实验研究

用W6/ 3 2单抗对JEG 3细胞进行免疫荧光染色 ,可见在JEG 3细胞膜表面有高强度的黄绿色荧光。HLA G+的JEG 3细胞作为刺激细胞 ,观察其对淋巴细胞增殖反应的影响 ,结果JEG 3细胞不能刺激淋巴细胞增殖。采用经典的单向混合淋巴细胞培养的方法 ,以转染及未转染HLA G分子的K5 62细胞作为抑制细胞 ,按一定的比例加入反应体系 ,结果表明 ,转染HLA G的K5 62细胞能抑制淋巴细胞的增殖反应 ,该抑制以刺激细胞∶反应细胞∶抑制细胞的比例为 1∶1∶2时效果最明显 ,抑制率为 5 4 1% (P <0 0 1) ,转染空质粒和未转染HLA G的K5 62细胞均无明显抑制作用。外周血淋巴细胞与JEG 3细胞共同孵育 ,碘化丙啶 (PI)染色 ,流式细胞仪观察 ,结果发现 ,HLA G分子能诱导淋巴细胞的凋亡。     

HLA-G与免疫耐受

HLA-G是一种非经典人类主要组织相容性复合物Ⅰ类分子,与器官移植、生殖及肿瘤等多种免疫反应有关,是引起免疫耐受的一种因子.     

Immuno-inflammatory cell dynamics during cutaneous wound healing

The process of wound healing begins with an inflammatory reaction that is principally dependent on cellular immune elements. Although the involvement in wound healing of leucocytes that mediate nonspecific immunity (e.g. neutrophils and macrophages) is well known, the participation of cells which prime the immune reaction, i.e. the lymphocytes, requires further investigation. This study was performed to examine the temporal sequence and kinetics of these cells during cutaneous wound repair. The model selected was a full-thickness skin excisional wound made on the flanks of female Wistar rats. At time points ranging from 3 h to 2 wk wound samples were processed for polyester wax-embedding. Target antigens were identified and monitored quantitatively in sections stained immunohistochemically. Monoclonal antibodies against neutrophils, macrophages, pan T cells and cytotoxic populations of lymphocytes were used. The results showed that these cells are involved in the process of wound healing in a distinctive dynamic pattern. The accumulation of CD3⁺ T lymphocytes in the wound bed was mainly associated with the phase of granulation tissue formation. Intraepithelial CD3⁺ T lymphocytes were detected in considerable numbers within the regenerating epidermis. The cytotoxic cell populations (OX8⁺) were classified morphologically into the cytotoxic/suppressor subset of T cells and NK cells. The OX8⁺ T cells were shown to have a kinetic pattern similar to CD3⁺ T lymphocytes but of a lower magnitude. The accumulation of OX8⁺ NK cells was confined to the early inflammatory phase of repair. It is concluded that CD3⁺ T lymphocytes as well as OX8⁺ cytotoxic populations of the immune system are involved in the process of cutaneous wound healing in temporal sequences which suggest that they may be involved in its modulation.     

HLA-G expression by tumors

PROBLEM: It has been proposed that the expression of the non-classical MHC class I antigen, HLA-G, by trophoblast is one mechanism by which the placenta evades attack by maternal uterine NK cells. A similar mechanism is thought to be operative in the escape from immunosurveillance by tumor cells. However, data on the expression of HLA-G by tumor cells are highly conflicting. METHOD OF STUDY: In the present study, we have examined tissue sections from a wide variety of tumors by immunohistology and also several cell lines by flow cytometry and RT-PCR. Whilst very faint bands were detected in three cell lines (hepG2, Mead, CaSki) by RT-PCR, no tumors or cell lines were observed to express HLA-G protein. Furthermore, we found that tumor deposits are not usually infiltrated by NK cells. CONCLUSION: Our observations, therefore, do not support the proposal that tumor cells express HLA-G in order to evade host NK cell cytolysis.     

Lymphoid lineage cells in adult murine bone marrow diverge from those of other blood cells at an early,hormone-sensitive stage

Advances in cell sorting and GFP knock-in technology have made it possible to identify rare hematopoietic cells in murine bone marrow that are undergoing lymphocyte fate specification. Steroid hormones also represent important research tools for investigating relationships between different categories of lympho-hematopoietic precursors. By selectively blocking entry into and progression within lymphoid lineages, the hormones probably have a major influence on numbers of lymphocytes that are produced under normal circumstances. These issues are discussed within the context of developmental age-dependent changes that occur in the lymphopoietic process.     

Ly49A expression on T cells alters T cell selection

Ly49 receptors are inhibitory receptors expressed on subsets of both NK cells and NK1.1(+) T cells. The function of these receptors on NK cells is believed to be important in maintaining self-tolerance, yet their role on T cells is unclear. In this report we investigated how an Ly49A transgene alters T and NK cell development in an in vivo environment, where a ligand for Ly49A is expressed. Ly49A transgenic mice that co-expressed an MHC ligand for Ly49A, H-2D(d), developed a severe inflammatory disorder that resulted in death within the first weeks of age. T cells expressing forbidden TCR V(beta) chains were found both in the thymus and periphery of transgenic mice, while non-transgenic littermates had successfully deleted these T cell subsets. These data indicate that the expression of Ly49A on T cells could alter T cell selection and allow survival of potentially self-reactive T cells.     

Analysis of Peripheral Blood Lymphocyte Subsets,NK Cells,and Delayed Type Hypersensitivity Skin Test in Patients With Premature Ovarian Failure

PROBLEM : Premature ovarian failure (POF) probably belongs to the group of autoimmune endocrinopathies. Cell-mediated immune parameters were investigated. Sex steroids have a profound effect on the immune system. POF patients and postmenopausal control women (PM) were tested with or without estrogen substitution. METHOD : A novel FACS analysis system (using double labeling techniques) was used in 30 patients with POF to enumerate the subjects of peripheral blood lymphocytes and NK cells. Eighteen PM women and 30 healthy men and women served as controls. We also tested the delayed type hypersensitivity skin test (DTH) toward Candida in the POF patient group to be informed on their cell-mediated immune function. RESULTS : The numbers of blood lymphocytes, CD3⁺, CD4⁺ and CD8⁺ T cells, were not abnormal in POF patients. However, HLA-DR⁺ T cells were increased in POF patients and in PM women (P<0.05). These elevated numbers were partially reversible by estrogen substitution. The number of CD19⁺ cells (B cells) was elevated, whereas CD3^?/CD16⁺/CD56⁺ cells (NK cells) were decreased in POF patients (P<0.05), irrespective of estrogen substitution. DTH skin tests toward 0.1% Candidin (0.1 ml intradermal injection) were negative in 11 out of 20 tested POF patients, compared to only 2 out of 10 tested controls (P<0.05). CONCLUSION : POF patients show numerous immune cell abnormalities. These abnormalities were only partially due to estrogen deficiency. We hypothesize that these abnormalities either lead to ovarian autoimmunity or may have direct effects on the ovarian function.     

Divergences in KIR2D+ natural killer and KIR2D+CD8+ T-cell reconstitution following liver transplantation

Natural killer (NK) and CD8(+) T cells may be active elements in the allograft response, but little is known about their role in liver transplantation. Some of these cells express killer immunoglobulin-like receptors (KIRs), which after binding specific ligands may transmit inhibitory/activating signals. In this study, circulating NK and CD8(+) T cells expressing CD158a/h (KIR2DL1/S1) or CD158b/j (KIR2DL2/3/S(2)) receptors were analyzed in 142 liver recipients by flow cytometry. They were underrepresented in patients before transplantation, but following transplantation, whereas the KIR2D(+) NK subsets experienced a late recuperation (day 365) mainly in C2-homozygous patients developing early acute rejection, recovery of the 2 CD8(+)KIR2D(+) T cells started earlier, showing significant differences on day 365 between patients without acute rejection and those suffering from it (p = 0.004 and p < 0.0001, respectively). These differences were also evident when the human leukocute antigen-C genotypes of the recipient were considered. In conclusion, whereas the late recovery of KIR2D(+) NK cells in C2/C2 patients appears to be linked to acute rejection, the increase in early CD8(+)KIR2D(+) T cells in overall liver recipients correlates with a most successful early graft outcome. Therefore, monitoring of KIR2D(+) cells appears to be a useful tool for liver transplant follow-up.     

IL-2 production by dendritic cells is not critical for the activation of cognate and innate effectors in draining lymph nodes

Dendritic cells (DC) are unique antigen-presenting cells capable of triggering NK cell effector functions and priming naive T cells in vivo. Microbial stimulation induces early IL-2 production by mouse DC. Previous reports demonstrated that IL-2 is enriched at the site of DC/T cell interaction and promotes allogeneic T cell proliferation. However, the direct role of DC-derived IL-2 in the differentiation of cytotoxic T lymphocytes and in NK cell triggering in vivo has not been investigated. Lipopolysaccharide (LPS) stimulation of mouse bone marrow-derived DC results in early IL-2 production unless IL-4 is introduced in DC cultures. Here we show that IL-2 produced by LPS-activated DC is dispensable for cognate T cell responses since IL-2 loss of function DC elicit OVA-specific Tc1 effector and memory lymphocytes in draining lymph nodes in a setting where ex vivo cultured DC do not transfer antigens to host DC. Moreover, adoptively transferred IL-2 loss of function DC maintain their capacity to trigger NK cell proliferation/recruitment in lymph nodes. Therefore, immediate inducible IL-2 production by DC following microbial infection might play a regulatory role at ports of entry rather than in secondary lymphoid organs.     

Aging of the immune system: Focus on inflammation and vaccination

Major advances in preventing, delaying, or curing individual pathologies are responsible for an increasingly long life span in the developed parts of our planet, and indeed reaching eight to nine decades of life is nowadays extremely frequent. However, medical and sanitary advances have not prevented or delayed the underlying cause of the disparate pathologies occurring in the elderly: aging itself. The identification of the basis of the aging processes that drives the multiple pathologies and loss of function typical of older individuals is a major challenge in current aging research. Among the possible causes, an impairment of the immune system plays a major role, and indeed numerous studies have described immunological changes which occur with age. Far from the intention of being exhaustive, this review will focus on recent advances and views on the role that modifications of cell signalling and remodelling of the immune response play during human aging and longevity, paying particular attention to phenomena which are linked to the so called inflammaging process, such as dysregulation of innate immunity, altered T‐cell or B‐cell maturation and differentiation, as well as to the implications of immune aging for vaccination strategies in the elderly.