Insight into B cell development and differentiation

The main topic of this article is B cell development and differentiation, with a special focus on the mechanisms and molecules that regulate the expression of humoral immunity. Molecular epidemiological analysis was performed on the genes responsible for the X-linked agammaglobulinemia (XLA) phenotype of the majority of Italian patients and their distinct mutations were characterized. Mutations in Bruton's tyrosine kinase (BTK), a member of Tec Family of protein tyrosine kinases, have been found to be mainly responsible for XLA disease. The exact function of BTK in signal transduction is not yet known; thus, the specific role of BTK in receptor-dependent calcium signaling and the pro-antiapoptotic regulatory activity was addressed by transfecting RAMOS-1, a BTK-deficient human Burkitt's/B cell leukemia line with wild-type and mutant constructs. This work may provide clues about critical sites in the molecule and give support for gene therapy as a potential successful approach to XLA. Another aspect of this research is the identification and dissection of the molecular events that are likely to be directly related to the ability to express various isotypes of immunoglobulin with differing function and certain B cell immunodeficiency, mainly common variable disease and non-X-linked hyperIgM. B cell development and maturation steps in different compartments of the immune system are tracked by the analysis of cell-surface molecules and components of the signal transduction pathways, i.e. CD40, CD30, CD27, CD38, CD22 and CD24. A few components involved in B cell development, maturation and differentiation and their specific functional role are at least partially known, but these are far from fitting into an understandable pathway at present.     

B cell-dependent T cell development

T and B cells are thought to develop independently. While it is widely recognized that T cells help B cells in the production of antibodies to protein antigens, less well understood is whether or how B cells contribute to T cell development and function. Defects in cell-mediated immunity in individuals with B cell deficiency and in B cell-deficient mice suggest that B cells contribute to T cell function. The question of whether T cell development is B cell dependent was revisited using two novel mouse strains: mice with monoclonal T cells (MT) and mice with monoclonal compartments of both B and T cells (MBT). It was found that T cell development and thymocyte selection is modified by the presence of B cells. These results suggest that B cells, or B cell products, contribute to thymocyte selection and T cell development.     

New insights into the functions of B cells

Abstract:  Organ transplants between genetically different individuals elicit powerful immune responses that invariably cause rejection in the absence of immune suppression. Among the immune responses elicited by organ allografts, B-cell responses causing antibody-mediated rejection are one of the most vexing. However, recent advances in the field indicate that B cells and antibodies' contribution to immunity extends well beyond the traditional functions ascribed to antibodies. Here we review "non-humoral" functions of B cells and the implications of these functions to transplantation.     

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目的探讨儿童慢性乙型肝炎T细胞亚群与病毒复制水平、肝功能及肝组织病理之间的关系。方法甘肃省人民医院儿科和兰州大学第一医院感染科按门诊和住院就诊的先后顺序选择慢性乙型肝炎病毒(HBV)-DNA阳性124例中乙型肝炎患儿,其中男84例,女40例。124例中HBV携带者65例、慢性乙肝59例(轻度31例、中度18例、重度10例),对患儿均进行外周血T细胞亚群、cccDNA、DNA、乙肝病毒标志物、肝功检测,对其中的46例行肝组织病理学检测。同时以60例HBsAg(-)患儿作为正常对照组。结果各组乙肝患儿外周血CD3+,CD4+及CD4+/CD8+明显低于正常对照组(F值分别为13.26、12.34、14.73,P均<0.01),CD8+高于正常对照组(F=-11.87,P<0.01),携带者组和轻度组CD3+,CD4+及CD4+/CD8+明显低于中度组和重度组差,异有统计学意义;中、重度慢性乙肝患儿HBVcccDNA阳性率,高于携带者和轻度组(F=25.429,P<0.01);HBVcccDNA阳性组及HBeAg(+)组分别与HBVcccDNA阴性组及HBeAg(-)组比较,CD3+,CD4+,CD4+/CD8+均减低,CD8+均细胞增高,均有统计学意义,CD8+随病毒载量升高而增加(F=-11.43,P<0.01),CD3+,CD4+,CD4+/CD8+随其增加而降低(F值分别为12.42、13.87、12.75,P均<0.01);转氨酶异常组和转氨酶正常组比较,CD3+、CD4+、CD4+/CD8+下降(t值分别为15.28、14.63、27.74,P均<0.01),CD8+细胞增高(t=-16.39,P<0.01),有统计学意义;CD3+、CD4+、CD4+/CD8+随炎性和纤维化程度加重有升高趋势(t值分别为9.25、11.85、26.34,P均<0.01),CD8+随炎性和纤维化程度加重呈下降趋势(t=-10.18,P<0.01)。结论 T细胞免疫功能紊乱与病毒复制水平、肝功能及肝组织病理有一定关系,HBV活跃复制加重免疫功能紊乱,免疫功能的恢复,一方面可清除病毒,一方面引起肝组织病理改变。     

A case of prolonged human parvovirus B19 DNA-emia associated with polyclonal B cell activation

The current paper reports an 8 year old girl with arthralgia and polyclonal B cell activation induced by human parvovirus B19 infection (HPV B19). The infection was diagnosed by the presence of the virus genome in sera. The patient presented with transient arthritis in the wrist, ankle joint and neck and elevation of immunoglobulin IgM antibodies to HPV B19 and rubella, antibodies to Mycoplasma and antistreptolysin O but without the typical clinical features of erythema infectiosum. The polyclonal B cell activation was paralleled by the presence of the virus genome of HPV B19 in sera. In some children with arthralgia, it is important to examine the genomes of viruses that may cause arthritis as well as the antibody titers to the viruses.     

B细胞及永生B细胞在传染性单核细胞增多症患儿中的动态变化

目的探讨儿童传染性单核细胞增多症(IM)不同时期永生B细胞(CD19 CD23 )及B细胞(CD19 )的变化及其规律。方法在病程急性期,病程1、3、6个月分别采集30例IM患儿外周静脉血2mL,并分离单个核细胞,采用流式细胞术检测IM患儿及健康对照组儿童外周血单个核细胞CD19 CD23 及CD19 分子表达。结果IM患儿急性期CD19 CD23 [(0.24±0.13)%]及CD19 [(3.89±1.32)%]细胞明显降低,与其余各期及健康对照组比较均有显著差异(Pa<0.001);随时间推移及感染控制CD19 CD23 及CD19 逐渐升高,但病程1个月[CD19 CD23 (0.68±0.32)%,CD19 (8.63±2.15)%]仍低于病程3个月[CD19 CD23 (1.60±0.51)%,CD19 (15.27±3.92)%]、病程6个月[CD19 CD23 (1.30±0.50)%,CD19 (14.60±4.80)%]及健康对照组[CD19 CD23 (1.35±0.42)%,CD19 (18.91±3.53)%](Pa<0.001);病程3个月、6个月CD19 CD23 及CD19 细胞比较无显著性差异(Pa>0.05);病程3个月和6个月CD19 CD23 与健康对照组比较无显著性差异(Pa>0.05),但CD19 仍低于健康对照组,有显著性差异(Pa<0.001)。结论IM患儿急性期存在继发性体液免疫功能低下,并持续至临床症状消失后较长时间,该结果为临床应用静脉丙种球蛋白治疗IM提供了理论依据;为探索正常免疫个体永生B细胞被有效控制的机制提供了一个人体模型。     

Quantitation of the B and A cell fractions in human pancreas from early fetal life to puberty

The morphological development of B and A cells in human pancreas was studied with immunoperoxidase stains in 172 cases ranging in age from 12 weeks of fetal life to puberty. Tissue was defined as polypeptide rich or poor to take account of the known islet heterogeneity in the gland. Pancreatic cell density was measured and B and A cell development was calculated in terms of (a) volume fraction and (b) density (μm²/100 nuclei). B cell density increased throughout fetal life to reach a peak at the postnatal age of 2 months, whereas A cell density was greatest in the 6 month fetus. The ratio of B to A cell volume fractions is approximately 1.5 throughout most of fetal life and rises postnatally to a stable value of 5 by the age of 2.5 years.     

B cell cytopenia in two brothers with hyper-IgD and periodic fever syndrome

We report on two brothers with hyperimmunoglobulinemia D (patient 1: serum immunoglobulin D [IgD] concentration initially 61 IU/ml, later on 340 IU/ml; patient 2: serum IgD concentration 144 IU/ml; normal <100 IU/ml, 97th centile) and periodic fever syndrome (HIDS). Both are compound heterozygous for the mevalonate kinase (MVK) mutations V377I and I268T. They developed significant B cell cytopenia (7%, 129/μl and 11%, 132/μl, respectively; normal ranges 12–22%, 300–500/μl) with hypogammaglobulinemia (IgG 5.48 g/l and IgG 5.22 g/l, respectively; normal range IgG 6–13 g/l). Furthermore, the clinical spectrum shows an interesting atypical autoinflammatory symptomatology. The therapy consisted of prednisone, azathioprine, and intravenous immunoglobulins (IVIG), which results in reduced incidence and severity of febrile attacks. Conclusion: The pathogenesis and clinical presentation of HIDS is still not fully understood and show a great variability. To our knowledge, severe B cell cytopenia in children with HIDS has not been reported before. Furthermore, the therapy of febrile episodes is still performed on an individual basis in affected patients.     

Possible polyclonal B cell activation in mucocutaneous lymph node syndrome

Immunoserological studies on polyclonal B cell activation were carried out on 39 patients with mucocutaneous lymph node syndrome (MCLS) and in age-matched healthy individuals. The incidence of anti-mite, P. acnes (Kato) and EB virus antibodies, recently proposed as aetiological agents by some investigators, was increased in the patient group. Serum immunoglobulin (Ig) M level and IgM-anti-dinitrophenyl (DNP) antibodies, which are considered to be parameters of polyclonal B cell activation, were determined in MCLS cases. The level of serum IgM in MCLS was significantly elevated (0.02<P<0.05). Levels of anti-DNP antibodies in seven cases of MCLS (18%) were significantly higher than those of the controls (P<0.01). Nine of the ten pair sera in MCLS showed a stage-dependent decrease in anti-DNP antibodies. These results suggest that polyclonal B cell activation occurs in MCLS.Abbreviations MCLS mucocutaneous lymph node syndrome - P. acnes Propionibacterium acnes - EB virus Epstein-Barr virus - D. farinae Dermatophagoides farinae - PBS phosphatebuffered saline - Ig immunoglobulin - RT room temperature - FITC fluorescein isothiocyanate - DNP dinitrophenyl - BSA bovine serum albumin - OD optical density     

脑源性神经营养因子及其受体在儿童发育行为疾病中的作用

脑源性神经营养因子是神经系统发育中的关键信号分子,与其特异性酪氨酸激酶受体B(TrkB)结合后可引发多种生理效应.目前作用机制尚不清楚,大量研究证明其可能与神经细胞生存、生长、分化、损伤后修复、凋亡等作用相关.该文分别对影响脑源性神经营养因子及其受体TrkB表达的因素,脑源性神经营养因子及其受体TrkB在儿童发育行为疾病中的作用及早期环境与二者表达的联系进行综述.     

儿童异基因造血干细胞移植术后乙型肝炎病毒免疫标记的变化

目的 了解儿童异基因造血干细胞移植（allo-HSCT）前后乙型肝炎病毒（HBV）免疫标记的变化情况,探讨供受者allo-HSCT前不同HBV免疫状态与allo-HSCT后受者HBV免疫标记变化的关系.方法 回顾性分析2010年1月-2012年6月在我院接受allo-HSCT治疗的130例儿童血液病患儿移植前后HBV免疫标记物（HBsAg、HBsAb、HBeAg、HBeAb及HBcAb）、HBV-DNA等临床资料,移植后随访中位时间18（6 ～36）个月.结果 （1）allo-HSCT前：HBsAg阴性患儿126例,阳性4例;HBsAb阳性患儿92例;HBsAg阳性供者6例,余均为HBsAg阴性供者.（2）allo-HSCT后：16例移植前HBsAb阴性受者移植后转为HBsAb阳性：66例移植前HBsAb阳性受者接受HBsAb阳性供者移植后,47例仍为HBsAb阳性,18例为HBsAb阴性,1例发生HBV再激活;21例移植前HBsAb阳性受者接受HBsAb阴性供者移植后,13例转为HBsAb阴性.（3）移植前供者HBsAb阳性,输注CD34＋细胞＞7.24×106/kg、移植前受者HBsAb滴度高低对移植后受者HBsAb转为阴性有显著影响,P值分别为0.005、0.040和0.000.（4）2例移植前合并HBV感染患儿移植后发生HBV再激活,2例移植前无HBV感染患儿接受大三阳供者移植后继发HBV感染.结论 HBsAb阴性患儿接受HBsAb阳性供者allo-HSCT后,在造血和免疫功能重建的同时,其体内可产生针对HBV的保护性抗体;移植后受者HBsAb随时间逐渐丢失,丢失的比例与移植前受者HBsAb滴度高低、输注CD34＋细胞数高低、供者HBsAb阳性与否明显相关.因此,移植前对供受者进行针对HBV的免疫接种及移植后免疫重建后对受者再次免疫接种有利于预防移植后HBV激活及感染.     

Development of diffuse large B cell lymphoma during the maintenance therapy for B-lineage acute lymphoblastic leukemia

Non-Hodgkin lymphoma (NHL) is a very rare complication of acute lymphoblastic leukemia (ALL). A Japanese boy presented with B-lineage ALL at the age of 2.5. He was treated with chemotherapy for standard-risk ALL. While he was receiving maintenance treatment 2 years and 9 months after the diagnosis of ALL, diffuse large B cell lymphoma (DLBL) was diagnosed from a biopsy of an abdominal mass. DLBL was treated by surgical resection followed by chemotherapy for 6 months. The patient has been free from the recurrence of ALL or DLBL for 16 months after the development of DLBL.     

Sustained seroconversion of chronic hepatitis B infection after stem cell transplantation

Serap A, Funda O, Bengu K, Mehmet K, Nazan C, Rasit Y, Savas K. Sustained seroconversion of chronic hepatitis B infection after stem cell transplantation.
Pediatr Transplantation 2011: 15: E92–E95. © 2010 John Wiley & Sons A/S. Abstract: We present an 18‐yr‐old adolescent with acute lymphocytic leukemia, who underwent peripheral blood SCT with serologically and histologically documented chronic hepatitis B infection. Prior and during the transplant process, lamivudine was administered orally and he underwent SCT with a twofold decrease in viral load at the time of transplant from his HLA full matched, HBV natural immune (anti‐HBs and anti‐HBc positive) donor. Successful engraftment was achieved and three months after SCT, HBV seroconversion was documented accompanied with an ALT flare. Chronic graft‐versus‐host disease coincided after the transplantation, and he has been on immunosuppressive treatment for 25 months with sustained HBV seroconversion. We assume that adoptive immunity transfer combined with antiviral treatment might also constitute sustained seroconversion in chronic HBV, besides the reported risk of reactivation.     

B cell-dependent T cell development

T and B cells are thought to develop independently. While it is widely recognized that T cells help B cells in the production of antibodies to protein antigens, less well understood is whether or how B cells contribute to T cell development and function. Defects in cell-mediated immunity in individuals with B cell deficiency and in B cell-deficient mice suggest that B cells contribute to T cell function. The question of whether T cell development is B cell dependent was revisited using two novel mouse strains: mice with monoclonal T cells (MT) and mice with monoclonal compartments of both B and T cells (MBT). It was found that T cell development and thymocyte selection is modified by the presence of B cells. These results suggest that B cells, or B cell products, contribute to thymocyte selection and T cell development.     

Regulation of pancreatic cell differentiation and morphogenesis

Abstract: Organogenesis requires tissue interactions to initiate the cascade of inductive and repressive signals necessary for normal organ development. Tissue interactions initiate the pancreatic lineage within the primitive foregut endodermal epithelium and continue to direct the morphogenesis and differentiation of the endocrine, exocrine and ductal portions of the pancreas. An understanding of the mechanisms controlling pancreatic growth would enable the development of alternative therapies for diseases such as type 1 diabetes.     

Disorders of sex development: update on the genetic background, terminology and risk for the development of germ cell tumors

Background  Considerable progress has been made on genetic mechanisms involved in disorders of sex development and on tumor formation in dysgenetic gonads. Clinical and psychological outcome of patients are, as far as evaluated, unsatisfactory at present. Guidelines are emerging in order to optimize long-term outcome in the future. Data sources  The information obtained in this review is based on recent original publications and on the experience of our multidisciplinary clinical and research group. Results  This review offers an update on our knowledge concerning gene mutations involving in disorders of sex development, on the renewed nomenclature and classification system, and on the mechanisms of tumor development in patients. Conclusions  The consensus meeting on disorders of sex development has renewed our interest in clinical studies and long-term outcome of patients. Psychological research emphasizes the importance to consider male gender identity wherever possible in cases of severe undervirilization. Patient advocacy groups demand a more conservative approach regarding gonadectomy. Medical doctors, scientists and governmental instances are increasingly interested in the set-up of international research collaborations. As a consequence, it is expected that new guidelines for the optimal care of patients will be proposed in the coming years.     

异基因造血干细胞移植后乙型肝炎病毒感染2例临床干预并文献复习

目的 加强对造血干细胞移植中HBV感染的重视,注重早期干预,提高移植成功率。方法 回顾性分析97例异基因造血干细胞移植患儿的临床资料,通过对2例HBV感染的诊治体会结合文献复习。结果 2001年5月至2008年5月在上海交通大学附属上海儿童医学中心接受异基因造血干细胞移植的97例患儿中,2例分别在移植后41 d（病例1）、15个月（病例2）发生HBV感染。病例1移植前肝功能正常,乙肝二对半检查阴性,回顾性分析发现该患儿移植时HBV正处于潜伏状态（HBV DNA 1.17×106 copies·mL-1）。该患儿乙肝来势凶猛,移植后41～43 d出现巩膜明显黄染并伴大量腹水,移植后46 d迅速发展至肝、肾功能衰竭,出现少尿,凝血酶原时间38.4 s,部分凝血酶原时间>120 s,凝血酶时间>100 s,Cr 251 μmol·L-1,ALT 3 195 U·L-1,血清总胆红素7 mg·L-1,直接胆红素2.8 mg·L-1,HBV DNA 1.08×108 copies·mL-1,经拉米夫定等积极治疗2周后好转。移植后130 d 随着移植物抗宿主病（GVHD）的复燃和免疫抑制药物的加强应用,HBV再度活跃,HBV DNA从原已控制的3.50×104 copies·mL-1逐升至2.05×106 copies·mL-1,移植后315 d出现HBV YMDD（+）变异株,遂予阿德福韦酯联合治疗至今(移植后3.5年),目前肝、肾功能正常。病例2白血病起病初及干细胞移植前均示HBs Ab(+)、HBc Ab(+)、HBe Ab(+),ALT和HBV DNA正常,移植后12个月发生慢性广泛性GVHD,加强抗排异治疗后于移植后15个月复查发现：ALT 168 U·L-1,HBV DNA升至5×108 copies·mL-1,出现HBs Ag（+）和HBe Ag（+）。予拉米夫定治疗至移植后4.5年,目前ALT 40～80 U·L-1,HBV DNA 1×103～1×104 copies·mL-1。结论 乙肝在移植患儿中并不少见,长期的免疫抑制治疗常使病情反复,加强病毒监测、重视早期干预至关重要;移植前HBV DNA 检测有助于发现潜伏期患儿;HBs Ab(+)、HBe Ab(+)和HBc Ab(+)患儿在强烈免疫抑制下仍有HBV复燃的风险。     

Pre-B Cells and B Lymphocytes in Human Cord Blood and Adult Peripheral Blood

The frequencies of pre-B cells and B lymphocytes subpopulations were studied in 43 cord blood and 21 adult peripheral blood samples using a direct immunofluorescence double staining method. We found pre-B cells in 40 out of 43 cord blood samples studied, a rate of 93%, and in 16 of 21 adult blood samples, a rate of 76%. The mean frequency of pre-B cells in cord blood lymphocytes was 0.7%, while that in adult blood lymphocytes was 0.2%. The pre-B cells in both groups were all small pre-B cells. The mean frequency of B lymphocytes in cord blood was 11.4%, higher than that in adult blood (5.4%). The difference in B lymphocyte frequency between cord blood and adult blood was exclusively due to high frequency of surface IgM-positive and IgD-positive B lymphocytes in the cord blood.     

Distribution of memory B cell subsets in peripheral blood of children with frequently relapsing nephrotic syndrome北大核心CSCD

目的观察记忆B细胞在频复发肾病综合征(frequently relapsing nephrotic syndrome,FRNS)患儿病程中分布变化。方法前瞻性选择2020年10月—2021年10月就诊于徐州医科大学附属医院儿科的原发肾病综合征(primary nephrotic syndrome,PNS)患儿35例,根据其糖皮质激素(glucocorticoid,GC)治疗后的反应及复发频次,分为FRNS组、非频复发肾病综合征(non-frequently relapsing nephrotic syndrome,NFRNS)组;选择同期15例体检儿童为健康对照组。比较各组GC治疗前后记忆B细胞变化,并与临床指标作相关性分析。结果治疗前,FRNS组、NFRNS组总B细胞、总记忆B细胞、IgD^(+)记忆B细胞、IgE^(+)记忆B细胞比例均较健康对照组增高,且FRNS组较NFRNS组增高明显(P<0.05);FRNS组类别转换记忆B细胞比例较NFRNS组及健康对照组降低(P<0.05);治疗后,FRNS组、NFRNS组总B细胞、总记忆B细胞、IgM^(+)IgD^(+)记忆B细胞、IgM^(+)记忆B细胞、IgE^(+)记忆B细胞、IgD^(+)记忆B细胞、IgG^(+)记忆B细胞比例较治疗前降低(P<0.05);类别转换记忆B细胞比例较治疗前增高(P<0.05)。FRNS组尿蛋白定量高于NFRNS组及健康对照组(P<0.05),FRNS组白蛋白水平低于健康对照组(P<0.05);FRNS组尿蛋白定量与类别转换记忆B细胞比例呈负相关,与IgE^(+)记忆B细胞比例呈正相关(P<0.05)。结论FRNS患儿存在记忆B细胞亚群的分布异常;而IgE^(+)记忆B细胞和类别转换记忆B细胞比例可作为FRNS患儿在GC治疗后复发的正相关和负相关因素。