TRAF3 enforces the requirement for T cell cross-talk in thymic medullary epithelial development

Induction of self-tolerance in developing T cells depends on medullary thymic epithelial cells (mTECs), whose development, in turn, requires signals from single-positive (SP) thymocytes. Thus, the absence of SP thymocytes in Tcra^−/− mice results in a profound deficiency in mTECs. Here, we have probed the mechanism that underlies this requirement for cross-talk with thymocytes in medullary development. Previous studies have implicated nonclassical NF-κB as a pathway important in the development of mTECs, because mice lacking RelB, NIK, or IKKα, critical components of this pathway, have an almost complete absence of mTECs, with resulting autoimmune pathology. We therefore assessed the effect of selective deletion in TEC of TNF receptor-associated factor 3 (TRAF3), an inhibitor of nonclassical NF-κB signaling. Deletion of TRAF3 in thymic epithelial cells allowed RelB-dependent development of normal numbers of AIRE-expressing mTECs in the complete absence of SP thymocytes. Thus, mTEC development can occur in the absence of cross-talk with SP thymocytes, and signals provided by SP T cells are needed to overcome TRAF3-imposed arrest in mTEC development mediated by inhibition of nonclassical NF-κB. We further observed that TRAF3 deletion is also capable of overcoming all requirements for LTβR and CD40, which are otherwise necessary for mTEC development, but is not sufficient to overcome the requirement for RANKL, indicating a role for RANKL that is distinct from the signals provided by SP thymocytes. We conclude that TRAF3 plays a central role in regulation of mTEC development by imposing requirements for SP T cells and costimulation-mediated cross-talk in generation of the medullary compartment.A major role of the thymus is the generation of a functional T-cell repertoire that is broadly responsive to foreign antigens but is self-tolerant. Through their role in exposing developing thymocytes to a spectrum of self-antigens, the stromal cells of the thymus are integral to this tolerization. Of particular importance in this process are the epithelial cells comprising the thymic medulla, the region of the thymus where thymocytes selected into the CD4 and CD8 single-positive (SP) lineages reside before emigrating to the periphery (reviewed in refs. 1–3). The importance of thymic medullary epithelial cells (mTECs) in the maintenance of self-tolerance is illustrated by the destructive autoreactivity that results from disruption of mTEC development (reviewed in ref. 4).Just as mTECs have a central role in shaping the developing T-cell repertoire, thymocytes, in turn, are vital to the development and maintenance of the mTEC compartment, a bidirectional interaction that has been termed cross-talk (5–7). A number of recent reports have characterized the CD4 SP thymocyte–stromal cell interactions that are critical for mTEC development (5–11). However, the mechanism that enforces the requirement for SP thymocytes in mTEC development has not been fully identified.We therefore addressed the signaling requirements that mediate the cross-talk required for mTEC development. Previous studies have implicated nonclassical NF-κB as a pathway important in the development of mTECs. It has been shown that mice lacking RelB, NIK, or IKKα, components of the nonclassical NF-κB pathway, have an almost complete absence of mTECs and exhibit resulting autoimmune pathology (12–16). Engagement of TNF receptor (TNFR) family members including CD40, LTβR, and RANK has been shown to activate nonclassical NF-κB signaling via a pathway regulated by several members of the TRAF family of adaptor/ubiquitin ligase proteins. TRAF3 has a unique role in inhibiting nonclassical NF-κB signaling in resting cells (17), and it has been demonstrated that deletion of TRAF3 in B cells results in constitutive activation of the alternative NF-κB pathway (18, 19). We therefore tested the possibility that TRAF3-mediated inhibition of alternative NF-κB is responsible for the failure of mTEC development in the absence of signals from SP thymocytes. We made the striking observation that deletion of TRAF3 in thymic epithelium is sufficient to allow RelB-dependent mTEC development in the complete absence of TCRαβ SP thymocytes. TRAF3 deletion is also capable of overcoming all requirements for LTβR and CD40 during mTEC development, but is not sufficient to overcome the requirement for RANKL, indicating an essential role for RANKL that is distinct from the signals provided by SP thymocytes. Together, these results demonstrate that mTECs can develop in the complete absence of SP thymocytes and that TRAF3 plays a critical role in imposing the requirement for cross-talk with SP thymocytes, thus linking the appearance of mature thymocytes to the development of the thymic medullary environment necessary for imposing self-tolerance.     

二烯丙基二硫化物诱导胃癌BGC823 细胞周期G2/M期阻滞的机制*

目的:以细胞周期作为抗癌药物新靶点的研究,可能是很有前途的。笔者的前期工作发现,二烯丙基二硫化物（diallyl disulfide,DADS）可抑制人胃癌BGC 823 细胞增殖,其增殖抑制与细胞周期G2/M期阻滞有关;DADS可能是通过抑制细胞分裂周期蛋白25C（Cell division cycle protein 25C,Cdc25C）、cyclinB 1 表达使部分BGC 823 细胞停滞在G2/M期,但G2/M期阻滞的机制还未完全阐明。本研究进一步探讨DADS诱导人胃癌BGC 823 细胞周期G2/M期阻滞的可能机制。方法:RT-PCR 检测Chk1 和Chk2 在mRNA 水平的改变;Western blot检测DADS处理BGC 823 细胞前后细胞周期相关蛋白ATM-RAD3 相关基因（ATM-RAD3-related gene,ATR ）、细胞周期检查点蛋白激酶1（checkpoint kinase1,Chk1）、细胞周期检查点蛋白激酶2（checkpoint kinase2,Chk2）表达和ATR 、Chk1、Chk2 的磷酸化程度;免疫共沉淀检测Chk1、Chk2 与Cdc25C 结合情况。结果:RT-PCR 检测显示,Chk1 和Chk2 的mRNA 水平在处理组与未处理组之间无显著性差异（P>0.05）。 Western blot检测显示,总Chk1 和Chk2 蛋白表达在细胞处理前后均无明显改变,但15mg/LDADS刺激BGC 823 细胞2h 后,处理组细胞Chk1 磷酸化程度明显增加,并呈时间依赖性（P<0.05）,而Chk2 磷酸化程度在处理组与未处理组之间无显著性差异（P>0.05）。 15mg/L DADS 作用15～120min,ATR 磷酸化程度明显增加,呈时间依赖性（P<0.05）,而ATR 表达无改变。免疫共沉淀分析表明,DADS 能促进BGC 823 细胞Chk1 与Cdc25C 结合,而对Chk2 与Cdc25C 结合无影响。结论:DAD诱导人胃癌BGC 823 细胞G2/M期阻滞与Chk1 的活化有关,DADS可能是通过激活ATR 、Chk1,调节Cdc25C 的表达引起人胃癌BGC 823 细胞G2/M期阻滞。      

Developing an Evidence-Based Exercise Guideline on Improving Shoulder Motion and Lessening the Severity of Lymphedema for Breast Cancer Patients after Axillary Lymph-Node Dissection

Exercise is proven to be effective, safe and the preferred intervention for improving the range of shoulder motion of breast cancer patients who have undergone surgery for axillary lymph-node dissection. The application of evidence-based guidelines to clinical practice can help healthcare professionals to provide good quality care to patients and, in turn, produce better patient outcomes. The purpose of the present paper is to describe the development process of an evidenced-based guideline. Challenges in the implementation of evidence-based practice are identi.ed and strategies for tackling them discussed.     

Prevalence and characteristics of aquagenic pruritus in a young African population

Background

The internet is an increasingly important tool for physicians, but the extent to which it is used by dermatologists is unknown. We aimed to investigate the utilization of the internet by dermatologists in Saudi Arabia for medical purposes during their daily practice and to clarify the reasons for its use and non-use.

Methods

A self-administered questionnaire was distributed to all 160 dermatologists attending the National Dermatology conference in 2007.

Results

A total of 107 questionnaires were completed. Sixty-two percent of respondents had access to the internet in the workplace. The use of the internet to update medical knowledge was reported by 91%. Only 27% had internet access in consultation rooms. The majority of information retrieval occurred outside patient consultation hours (91%). Only 13% reported using the internet during patient consultation. Possible reasons included: lack of access (54%), time pressure (37%), possible interference with the physician-patient relationship (30%), and that use of the internet was too time-consuming (10%). The mean searching time used to solve a clinical problem was 34 ± 3 minutes. Fifty-eight percent used Pubmed; however, 77% of the dermatologists had no training at all in how to use this tool.

Conclusion

Professional medical use of the internet is widespread among dermatologists in Saudi Arabia. Providing access to the internet in the workplace and training of dermatologists to perform effective electronic searches are badly needed to improve the professional medical use of internet, which is expected to lead to better delivery of patient care.     

关于儿童死亡焦虑的初步探讨

利用斯皮尔伯格儿童状态焦虑的图示式、死亡刺激和脸谱对三组４９名儿童进行了死亡焦虑研究。结果表明，不同年龄组死亡焦虑得分存在明显差异，且焦虑水平随被试年龄的增加而升高。不同年龄的儿童对死亡对象的焦虑程度也不同。     

Chromosome aberrations and prognostic factors in therapy-related myelodysplasia and acute nonlymphocytic leukemia

Cytogenetic studies of 91 consecutive patients with therapy-related myelodysplasia or overt acute nonlymphocytic leukemia disclosed characteristic defects of chromosome 7 in 48 cases and of chromosome 5 in 21 cases. The chromosome 5 abnormalities were consistently present in all abnormal mitoses at the time of diagnosis, as were the chromosome 7 abnormalities in 45 of the 48 patients. Various abnormalities, primarily of the short arm of chromosome 17, were observed in 13 cases, abnormalities of the long arm of chromosome 21 were observed in 12 cases, and rearrangements of 11q23 were seen in nine cases. Thirteen patients presented a normal karyotype. Previous therapy with alkylating agents, the presence of an initial myelodysplastic phase, and abnormalities of chromosome 7 or 5 were interdependent. Patients with 11q23 rearrangement typically developed overt leukemia of FAB types M4 or M5a without myelodysplasia and with a short latent period. Evaluated by Cox regression analysis, complete remission of the primary malignancy and a malignant lymphoma as primary tumor were the two most important and independent prognostic factors indicating a longer survival (P = .008). In addition, the platelet count at diagnosis was a significant prognostic factor (P = .01). For the subgroup of 62 patients with myelodysplasia, the number of chromosome aberrations, the percentage of blasts in the bone marrow, and the hemoglobin level were other significant and independent prognostic factors (P = .05, .05, and .004, respectively). The most important predictive factor for a favorable response to intensive antileukemic chemotherapy in overt leukemia was the absence of a preceding myelodysplastic phase (P = .0014).     

PRIMARY PERITONITIS IN A PARAPLEGIC PATIENT

SUMMARY This report of a paraplegic patient with a primary peritonitis illustrates the difficulty in diagnosis and management these patients pose.