黄芪多糖诱导脐血单核细胞向树突状细胞分化中的作用

目的 观察NF-κB在黄芪多糖(APS)诱导脐血单核细胞向树突状细胞(DCs)分化过程的作用,探讨APS诱生DCs过程中的信号传导通路.方法 无菌条件下采集脐血,密度梯度离心法获得脐血单核细胞分为3组.对照组:在无药物的RPMI 1640完全培养液中培养;APS组:在含有黄芪多糖100mg/L的RPMI 1640完全培养液中培养;PDTC组:用NF-κB的抑制剂吡咯烷二硫氨基甲酸酯(PDTC)10μmol/L处理脐血单核细胞30 min后,加入含有黄芪多糖100 mg/L的RPMI 1640完全培养液中培养.培养过程中用倒置光学显微镜和透射电镜观察细胞形态变化;收集培养第12天的细胞,FCM检测细胞免疫表型;免疫荧光显微镜下观察细胞内NF-κB的激活、迁移情况.结果 (1)对照组细胞无成簇生长,培养至第12天细胞呈梭形巨噬细胞形态;黄芪多糖组细胞成簇生长,形态学由圆形逐渐变为典型的树突状细胞形态;抑制剂组细胞生长缓慢,未出现聚集现象,细胞形态学未见明显变化.(2)APS组高表达DCs特异性抗原CD80、CD83和CD86,与对照组、PDTC组比较差异有统计学意义(P<0.01),对照组与PDTC组表达相似,二者差异无统计学意义(P>0.05).(3)免疫荧光显微镜下观察NF-κB可见APS组伴有大量NF-κB荧光进入细胞核,尤以72 h显著,NF-κB激活率为(75.20±7.37)%,而对照组、PDTC组NF-κB激活率分别为(13.20±3.46)%、(8.20±1.92)%,与APS组相比,差异有统计学意义(P<0.01).结论 黄芪多糖能够诱导脐血单核细胞定向分化为DCs,NF-κB是黄芪多糖诱导脐血单核细胞向DCs分化的信号传导通路中的关键元件.

Abstract：

Objective To investigatethe role of NF-κB played in the process of the cord blood monocytes differentiating into dendritic cells(DCs)induced by astragalus polysaccharide(APS)and to explore the signal transduction pathway involved in this process.Methods Umbilica]cord blood was collected in aseptic conditions.The cord blood monocytes were obtained by density gradient centrifugation and were divided into three groups afterwards.In the control group.cells were cultivated in the RPMI 1640 complete medium.In the APS group.cells were cultivated in the RPMI 1640 complete medium containing 100 mg/L APS.In the PDTC group:cells were treated with 10 μmol/L disulfide carbamate(PDTC).NF-κB inhibitor in 30 min followed by cultivalion in the RPMI 1640 complete medium containing 100 mg/L APS.,The morphological changes were observed during the process of cultivation by the optical microscope and transmission electron microscopy.Cells were collected 12 d later and the cellular immunophenotyping was assayed by FCM.,The activation and migration of NF-κB fluorescence in the cells was examined by the immunoflouresce microscopy.Results (1)Cells in the control group grown up without cluster forformation and were found fusiform and macrophage-like in 12 d.Cells in the APS group grown up in clnstem,and morphological changes were found from the circular shape to a typical dendritic cells-like shape.Cells in the inhibitor group grown up slowly and without cluster formation,and cell morphdogy had no significant change.(2)The expression of DCs-specific antigen CD80,CD83 and CD86 in the APS group was higher than that in the control group and inhibitom group(P<0.01).The expression of those antigen in the control group and PDTC group was similar and had no statistically significance(P>0.05).(3)NF-κB fluorescence in the nuclei was examined by the immunoflourescence microscopy and was much higher in the APS group than that in khe other groups,especially in 72 h with the activation rate of NF-κB (75.20±7.37)%,while(13.20±3.46)% of PDTC group and(8.20 ±1.92)%,respectively(P<0.01).Conclusion Astragalus polysaccharide can induce the differentiation of umbilical cord blood cells into DCs,and NF-κB is the key component of the signal transduction pathway involved in this process.     

肿瘤抗原联合CD40L致敏树突状细胞诱导CTLs杀伤K562细胞的实验研究

目的：以健康人外周血单核细胞为前体细胞，体外诱导为树突状细胞（DCs），负载K562细胞冻融抗原，并联合CD40L诱导产生特异性细胞毒性T淋巴细胞（CTLs）对K562细胞的杀伤作用。方法:密度梯度离心法、贴壁法分离健康人外周血单核细胞，应用rhGM-CSF、rhIL-4、rhTNF-α等细胞因子诱导扩增，培养DCs，用K562细胞冻融抗原联合rhsCD40L致敏DCs。实验分4组：K562细胞冻融抗原致敏DCs为实验组A，联合CD40L致敏DCs为实验组B，未致敏DCs为对照组A，单核细胞+异体淋巴细胞组为对照组B，观察CTLs对K562细胞的杀伤效应。结果:培养出具有典型特征的DCs，表达CD40最高达96%、CD86达97%、CD80为77%、CD1a为 69%，体外能诱导强烈的同种异体混合淋巴细胞增殖反应。在效靶比为 20∶1 时，实验组A对K562细胞的杀伤率为71.3%，实验组B为86.9%，对照组A为37.6%，对照组B为21.1%。实验组均显示高水平杀伤率，与对照组比较差异显著（P＜0.05），实验组B加CD40L杀伤率高于实验组A（P＜0.05） 。结论：K562细胞冻融抗原冲击致敏DCs能有效诱导T细胞特异性抗白血病作用，联合CD40L能增强其CTL的杀伤作用。     

罗勒多糖对树突状细胞表面分子表达的影响

目的：观察罗勒多糖对人外周血单核细胞来源的树突状细胞（Dendritic cell，DC）表面分子表达的影响，探讨其抗肿瘤免疫机制。方法：从正常人外周血分离获得单核细胞，加入含10％胎牛血清、CM-CSF及IL-4的RPMI1640，37℃培养5天，实验组加入罗勒多糖，对照组加入PBS，流式细胞仪检测细胞表面分子的表达。结果：在细胞因子的诱导下，CD14^＋单核细胞逐渐分化为DC，罗勒多糖作用组与对照组DC均表达CD209、CD80、CD83、CD86、CD1a和HLA-DR，与对照组相比，罗勒多糖组DC表面分子CD80和HLA-DR的表达均明显上调。结论：罗勒多糖能够调节DC表面分子CD80和HLA-DR的表达，这可能是罗勒多糖发挥其抗肿瘤免疫的机制之一。     

干扰素-α联合GM－CSF诱导慢性髓性白血病细胞向树突状细胞分化

目的：研究干扰素-α（IFN-α）对慢性髓性白血病（CML）骨髓单个核细胞来源的树突状细胞（DCs）发育的影响。 方法： 12例初发慢性期CML患者的骨髓单个核细胞，分别与含如下细胞因子,RPMI-1640培养液共育：rhGM-CSF 1×106U/L联合rhIFN-α 2×106U/L（IFN-α组）、rhGM-CSF 1×10⁶U/L联合rhIL-4 5×10⁵U/L（IL-4组）、单用rhGM-CSF 1×10⁶U/L和单用rhIFN-α 2×106U/L，培养7 d；于第8-10 d，部分孔加入rhTNF-α 5×10⁴U/L。形态学（Wright染色、倒置显微镜）、免疫学（CD80、CD86、CD83、CD1a、HLA-DR）检测；磷脂酰丝氨酸（PS）转位检测 DCs凋亡情况；荧光原位杂交（FISH）对1例CML进行细胞遗传学分析；混合淋巴细胞反应（MLR）检测刺激同种异体T淋巴细胞增殖的能力。 结果： CML骨髓单个核细胞经上述细胞因子诱导7 d后，IFN-α组和IL-4组均呈现树突状细胞的典型形态；免疫学鉴定，IFN-α组DCs CD80、CD86、CD83、HLA-DR的表达显著高于IL-4组（P<0.05），经5×104U/L rhTNF-α作用后，两组DCs CD80、CD86、CD83、HLA-DR进一步上调，其中IFN-α组DCs CD80、CD86、CD83、HLA-DR的表达显著高于IL-4组（P<0.05）；经FISH证实来源于白血病细胞；两组DCs均具有刺激同种异体T淋巴细胞增殖的能力，IFN-α组刺激淋巴细胞增殖的能力明显高于IL-4组(P<0.05)。 结论： IFN-α可促进CML骨髓单个核细胞来源的树突状细胞的分化、活化。这可能是IFN-α在CML中的治疗机制之一。     

脐血CD123+髓系树突状细胞的生物学特性研究

探讨人脐血单核细胞在髓系树突状细胞（DC）体外诱导体系中获得的CD123^＋髓系DC的生物学特性。分离脐血单核细胞，用人重组的粒／单核细胞集落刺激因子（GMCSF）和IL-4将其诱导为IX2。用流式细胞仪检测DC表面共刺激分子、CD123和CDllc的表达，并用间接免疫磁珠法将其中CD123^＋ DC加以分离纯化；激光共聚焦显微镜、扫描电镜和倒置显微镜观察CD123^＋ DC形态；^3H-TdR渗入法检测CD123^＋ DC对同种异体T细胞的刺激能力。脐血单核细胞经GM-CSF和IL4诱导7d后，细胞表面高度表达HLA-DR、CD86、CDllc和CD123，低表达CD83，丧失CD14的表达，其中CD123和CDllc均匀分布于DC表面。免疫磁珠纯化后的CD123^＋ DC呈现不成熟DC形态，除细胞体积较小外，其表面突起类似于CD123DC。CD123^＋ DC能明显刺激同种异体T细胞增殖，但其刺激能力较CD123 DC组低（P〈0．05）。GM-CSF和IL-4培养体系中的CD123^＋DC可能是DC分化发育过程中更早期的未成熟髓系DC，具有独特的生物学特性。     

人脐血源性MSCs成骨诱导分化后对DCs的免疫抑制研究

目的探讨人脐血源性间充质干细胞(mesenchymal stem cells derived from umbilical cord blood,UCB-MSCs)经成骨诱导分化后,对树突状细胞(dendritic cells,DCs)的分化、成熟及免疫功能的影响。方法对UCB-MSCs通过细胞形态、表面标记及成骨诱导分化能力进行鉴定;在外周血单核细胞培养体系中加入GM-CSF+IL-4+TNF-α,刺激DCs诱导分化及成熟;收集与成骨诱导分化前后UCB-MSCs共培养的DCs,流式细胞仪检测DCs免疫表型的表达情况;将成熟DCs作为刺激因素,外周血淋巴细胞作为反应细胞,3H-TdR标记β液体闪烁计数仪检测与成骨诱导分化前后UCB-MSCs共培养后,DCs刺激淋巴细胞增殖能力的变化。结果人UCB-MSCs成骨诱导分化后能抑制DCs表面CD40、CD80、CD83、CD86和MHC-II的表达,上调CD14的表达;DCs具有明显刺激淋巴细胞增殖的功能,而UCB-MSCs成骨诱导分化后能显著抑制DCs刺激的淋巴细胞增殖。结论成骨诱导分化的UCB-MSCs在体外可抑制同种异体DCs的分化、成熟及免疫功能,为UCB-MSCs作为同种异体源性种子细胞在骨组织工程中的应用提供了依据。     

钙载体诱导慢性髓系白血病细胞分化成树突状细胞

目的：探讨用钙离子载体（Calcium ionorphore，CI）A23187诱导慢性髓系白血病（CML）病人来源的白血病细胞分化成树突状细胞（Dendritic cells，DCs）的方法和条件。方法：选择外周血白细胞计数较高的CML病人，采集外周血或骨髓液分离单个核细胞，通过两次贴壁法除去单核细胞和淋巴细胞，然后放入含或不含GM-CSF（200ng／ml）和CI（375ng／ml）的RP-M11640培养液中培养96小时以上，通过流式细胞仪分析细胞表型、倒置显微镜和电镜观察细胞的形态变化来观察CI对白血病细胞诱导成树突状细胞的作用，初步摸索和探讨CI诱导白血病细胞转化成树突状细胞的最佳条件。结果：发现对CML病人外周血或骨髓液分离的白血病细胞加入GM—CSF（200ng／ml）、CI（375ng／ml）和含10％胎牛血清的RPMI1640培养96小时，细胞能获得典型的成熟树突状细胞的形态，CD86、CD80、CD40、CD83和HLA-DR的表达显著提高。结论：CML细胞用GM-CSF和CI联合诱导能获得成熟树突状细胞的典型形态特征和免疫表型。     

孕酮对人树突状细胞成熟和免疫功能的影响

目的：研究孕酮（P₄）对人外周血来源树突状细胞（DCs）成熟和免疫学功能的影响。方法：在人外周血来源DCs体外培养时加入两种浓度的P₄ (10-7 mol/L和10-6 mol/L)处理，光镜和电镜下观察DCs的生成情况及形态变化，以流式细胞仪分析各组细胞的免疫表型，用ELISA方法测定其分泌的IL-10和IL-12水平，［3H］-TdR掺入法检测体外混合淋巴细胞反应中DCs刺激同种反应性T细胞的增殖能力。结果：加入P4培养后, DCs树突状和膜面状伪足减少，表达低水平MHC-II分子和共刺激分子CD40、CD80和CD86，其分泌的IL-10水平升高，IL-12水平明显下降，DCs刺激同种反应性T细胞的功能显著下降。结论：P₄抑制人外周血来源DCs的成熟，对其免疫学功能具有负性调节作用。     

HBV S基因修饰树突状细胞疫苗诱导特异性CTL反应的探讨

目的分析腺病毒载体介导HBVS基因修饰树突状细胞（DCs）能否诱导抗HBV特异性CTL反应。方法制备携带HBVS基因的重组腺病毒，分别转染外周血诱导培养的DCs，观察腺病毒转染DCs效率和DCs中HBV抗原的表达；混合淋巴细胞反应测定HBV抗原基因修饰DCs刺激同种异体T淋巴细胞增殖能力；乳酸脱氢酶释放法检测特异性CTL细胞对HepG2 22．1．5靶细胞的杀伤能力。结果腺病毒载体能够高效介导HBVS基因在DCs中表达，且DC细胞形态完整；HBVS基因修饰DCs具有刺激同种异体T细胞增殖能力，同时能诱导抗HBV特异性CTL反应。结论HBVS基因修饰DCs疫苗具有增强抗HBV特异性CTL效应的能力，可能发展为一种新型抗病毒疫苗。     

丹参酮ⅡA 对树突状细胞表型的影响及对功能的调控

目的:提取小鼠骨髓树突状细胞(DCs),体外给予丹参酮ⅡA 干预,观察药物刺激后DCs 功能的改变,从而探讨丹参酮ⅡA 在免疫系统中的作用机制。方法:提取小鼠的骨髓DCs,体外给予10 ng/ ml GM-CSF 及IL-4 的完全培养液培养,并在第5 天,磁珠分选得到纯度90%以上的树突状细胞,体外给予一定浓度的丹参酮ⅡA 及LPS 刺激,收集细胞及上清,运用流式细胞技术检测DCs 表型,ELISA 方法检测细胞上清TNF-β、IL-12 含量变化,同种混合淋巴细胞反应检测树突状细胞刺激淋巴细胞增殖及分化的能力。结果:在丹参酮ⅡA 浓度为500 ng/ ml 时,药物对DCs 抑制作用达到最大,因此选取该浓度为实验作用浓度;即在500 ng/ ml 作用下,实验组与对照组相比,DCs 表达MHCⅡ、CD86 及CD80 水平均显著降低(P<0.05);实验组DCs 分泌的TNF-β及IL-12 含量均显著降低(P<0.05);实验组DCs 刺激淋巴细胞增殖反应能力明显降低(P<0.05);实验组DCs 刺激T 淋巴细胞分泌IL-4 含量明显高于对照组,IFN-β含量明显低于对照组(P<0.05)。结论:丹参酮ⅡA 可以通过降低LPS 诱导的DCs 成熟状态,来参与免疫系统或自身免疫性疾病的发生发展。     

Serotonin content is elevated in the immune cells of histidine decarboxylase gene knock-out (HDCKO) mice. Focus on mast cells

Objective: Biogenic amines, histamine and serotonin are present in the granules and nucleus of mast cells. We wanted to study the presence, amount and localization of serotonin in mast cells and other cells of the immune system, under conditions of histamine deficiency caused by knock out of histamine decarboxylase gene (HDCKO). Methods: Wild type and histamine deficient HDCKO mice were studied for serotonin content of the immune cells (lymphocytes as well as the monocyte-granulocyte-mast cell group) using flow cytometry and confocal microscopy. Groups of mice were kept either on complete rodent chow or on a histamine-free diet for a month before the experiments. Results: The amount of serotonin was significantly higher in the KO animals, irrespective of the diet. Confocal microscopy demonstrated the presence of serotonin in the nucleus of mast cells in the wild type animals, while it was not present in the KO mice. Furthermore, in the cytoplasm (granules) of KO mast cells a bright fluorescence was observed in contrast to the pale fluorescence of wild animals. Conclusion: It seems likely that serotonin replaces the deficient histamine in the heparin-biogenic amine complex in the mast cell granules. Received 21 June 2006; returned for revision 17 July 2006; returned for final revision 22 September 2006; accepted by G. Wallace 17 October 2006     

T follicular helper (Tfh) cells in lupus: Activation and involvement in SLE pathogenesis

Systemic lupus erythematosus (SLE) is a chronic systemic inflammatory autoimmune disease characterized by a breakdown of tolerance to self. The autoantibodies generated in SLE are directed against nuclear components, with which they form immune complexes (ICs). ICs play key roles in organ and tissue damage, as well as in the activation of the innate and adaptive immune system during the disease course. Therefore, it is of prime importance to understand the mechanisms responsible for the development of B cells producing these pathogenic autoantibodies. There is compelling evidence that T follicular helper (Tfh) cells play a fundamental role in this process. In this review, we will summarize the current knowledge regarding the involvement of Tfh cells in SLE pathogenesis, and discuss potential strategies to target Tfh cells and/or molecules as a therapeutic modality of SLE.     

The potential utility of methoxypoly(ethylene glycol)-mediated prevention of rhesus blood group antigen RhD recognition in transfusion medicine

Red blood cell (RBC) transfusions are an important clinical intervention. However, RBC express hundreds of non-ABO antigens making alloimmunization a significant risk. RhD expression is the most immunologically important non-ABO antigen. Availability of RhD⁻ blood, often problematic in North America and Europe, is a significant issue in Asia and Africa where RhD⁻ blood is uncommon (<0.5% of supply). The immunocamouflage of RhD is readily accomplished by the covalent grafting of methoxypoly(ethylene glycol) [mPEG] to the RBC membrane. To determine if RhD immunocamouflage would inhibit its immunologic recognition, an in vitro RhD-sensitized antigen presentation assay using PBMC and dendritic cells (DC) from RhD-sensitized women was used. The immunological effects of polymer grafting to an immunodominant RhD peptide, purified RhD protein and intact RhD⁺ RBC were examined via T cell proliferation and cytokine release assays. At Day 11, PEGylation significantly attenuated T cell proliferation arising from RhD peptide (∼80 → 5%), protein (36 → 0.2%) and intact RBC (33 → 1.4%). Cytokine secretion was similarly blunted following PEGylation of the purified protein or intact RBC. These data support the immunomodulatory effects of PEGylation and the potential utility of this technology in transfusion medicine - especially in situations where RhD⁻ blood is rare or in short supply.     

人脐血单个核细胞向神经细胞分化

目的：观察培养前后人脐血单个核细胞(MNCs)的形态学及免疫反应性变化，探讨其能否向神经细胞的分化及机制。方法：密度梯度离心脐血中单个核细胞，接种并用。EGF和bFGF刺激细胞生长，倒置显微镜下观察培养前后细胞形态变化，并行免疫细胞化学鉴定。结果：培养前脐血MNCs胞体小呈圆形，nestin阳性细胞、AP2阳性细胞散在分布(阳性率为1．5％和3．4％)无GFAP阳性细胞着色。培养14d后，细胞群中相邻细胞突起连成网状；AP2、GFAP染色阳性细胞成片状分布(阳性率33．5％和24．6％)，未见nestin阳性细胞。结论：脐血细胞中可能有多能干细胞，经体外培养后能分化为具有一定形态的神经细胞。     

妊高征患者外周血红细胞免疫功能的变化和血浆TXB2水平的相关性分析

目的:探讨妊高征患者外周血红细胞免疫功能的变化和血浆TXB2水平的相关性.方法:应用放射免疫分析和免疫法对33例妊高征患者进行红细胞免疫功能和血浆TXB2检测,并与35名正常人作比较.结果:妊高征患者RBC-C3bRR水平明显降低(P<0.01),而血浆TXB2水平显著升高(P<0.01),RBC-C3bRR与TXB2...     

Detection of OKT6-positive cells (without visible Birbeck granules) in normal peripheral blood

The specificity of a monoclonal antibody (OKT6) for peripheral blood mononuclear cells was examined by indirect immunofluorescence and ultrastructural immunogold labelling. Some rare peripheral blood mononuclear cells (approximately 1%) expressed T6 antigen on their membrane surface, as determined by light microscopy and cytofluorometry. Electron microscopic examination of immunogold-labelled cells revealed that OKT6-positive cells were dendritic, lacking the Birbeck granules and expressed variable density of the membrane T6 antigen. The relationship of such cells with Langerhans' cells is discussed.     

Telomere shortening in peripheral blood cells was related with aging but not with white blood cell count

Summary Telomeres in somatic cells are progressively shortened with aging. We investigated the relationship between the telomere length and other factors which may affect the frequency of cell divisions, in peripheral blood cells. Shortening of telomeric repeats was correlated with aging (p<0.0001), but not with white blood cell count, neutrophil count, and smoking habit. Not only the number of cell divisions, but also some other factors, such as upregulation level of telomerase activity concomitant with the cell division in hematopoietic progenitor cells, might affect the length of telomeric repeats in blood cells.     

The role of natural antibodies and ABO (H) blood groups in transplantation of human lymphoid cells into mice

Recently, evidence was presented that natural antibodies (NAb) are a crucial barrier to human cellular engraftment in severely immunosuppressed normal mice (Eur. J. Immunol. 1992.22:197.). In this report we show that normal mouse serum contains low titers of NAb against human cells of blood groups type O (H) and B and high titers against human cells of blood group A. Accordingly, human peripheral blood leukocytes (PBL) of group O (H) and B donors could be grafted successfully into normal BCBA mice (H-2^h/k) following irradiation with high dose total body irradiation (TBI). PBL of blood group type A donors did not engraft in normal mice but could be transplanted without difficulty in B cell-deficient CBA/N mice which lack NAb, after conditioning with high dose TBI. Treatment of lethally irradiated normal BCBA mice with cobra venom factor (COF), which eliminates the third factor of complement, and liposomes containing dichloromethylene diphosphonate (C1₂DMP), which eliminates macrophages, resulted in engraftment of human blood group type A PBL. This implies that the NAb barrier for discordant xenogeneic cell transplantation can be abrogated. A method utilizing directly labeled probes and flow cytometry is described for the quantitation in mouse serum of NAb, reacting with human cells. Using sera of H-2^b/k mice we show that murine NAb react with human stem cells, granulocytes, lymphocytes and monocytes of blood group A and only weakly with similiar cells from blood group O (H) and B donors. Sera of H-2^b, H-2^d and H-2^k mice of different ages and microflora possess NAb against human erythrocytes of blood group type A and occasionally demonstrate weak titers against erythrocytes of blood groups B and O (H) and the Rhesus factor.     

增殖细胞核抗原阳性细胞在幼年大鼠前脑的分布

目的　探讨幼年大鼠前脑内是否存在增殖细胞。方法　用增殖细胞核抗原 (PCNA)单克隆抗体PC10免疫组化研究。结果　PCNA阳性反应部位分两类 :一类为圆形或卵圆形深染颗粒 ,具有核的形态和大小 ,主要分布于吻侧迁移流、室管膜下带和部分血管壁 ;散在分布于尾壳核、运动皮质、隔区和斜角带 ;有时见“镜影核” ,主要存在于尾壳核 ;另一类为整胞体染色 ,见于室管膜、室管膜下带和吻侧迁移流。结论　幼年大鼠前脑内存在增殖细胞     

Regulatory T cells and regulatory natural killer (NK) cells play important roles in feto-maternal tolerance

In the early pregnancy decidua, lymphocytes express some activation markers on their surface, suggesting that maternal lymphocytes are activated and recognize the semiallograftic fetus. Therefore, the immunoregulation system must work to prevent fetus rejection. Recent data showed that parts of the immunoregulation system such as CD4⁺CD25⁺ regulatory T (Treg) cells, Th3 cells, Tr1 cells, regulatory NK cells, and a tryptophan-catabolizing enzyme, indolamine 2,3 deoxygenase, play very important roles in the maintenance of pregnancy. Not only Treg cells but also regulatory NK cells may inhibit maternal T cell or NK cell fetal attack.