9th American Society of Gene Therapy annual meeting

The American Society of Gene Therapy, under the presidency of Mark Kay, held its annual meeting in Baltimore, MD, USA this year. This meeting was well received by academics and industry alike in order to promote research, development and application of gene therapy. Exchange of information, promotion of education and development of clinical translation have been the main aims of this society. On face value, the meeting seems to highlight that gene-based treatment is coming of age. Many drawbacks of gene-based treatments were discussed at this meeting with an intense vigour. Immunology has been the major hurdle in restricting the full realisation of gene therapy in the clinical arena. In summary, the field of gene therapy has progressed from its infancy stage of trying to get it to work, to another stage where attempts are being made to overcome the problems associated with its application, in particular, in relation to human immune responses to the vector and the transgene. This progress should be celebrated and not treated as a failure of this form of therapy, as to make this progress is indeed an achievement for any form of therapy.

The role of 5′ untranslated region in translational suppression of OKL38 mRNA in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is the sixth most common cancer worldwide. OKL38 is a pregnancy-induced growth inhibitory gene and its expression is lost in various breast cancer cell lines and kidney tumor. To determine the role of OKL38 expression in HCC, we investigated its expression in various HCC samples and liver cancer cell lines. Western blot analysis revealed that OKL38 protein was absent or reduced in 64.2% (18 of 28) of the HCCs examined and four liver cancer cell lines. Immunohistochemistry study demonstrated that OKL38 protein was undetectable in 41.3% (38 of 92) of HCC, whereas 39.1% (36 of 92) of HCC showed low expression of the protein. Lost or reduced expression level of OKL38 protein was significantly correlated to high tumor stages in HCC (P=0.0042). Overexpression of the OKL38 caused cell death in Chang liver cells. 5' Untranslated region (5'UTR) deletion studies demonstrated that OKL38 was downregulated via translation suppression associated with the 5'UTR of its mRNA. Taken together, the 5'UTRs of OKL38 might play an important role in downregulation of its protein and the absence of OKL38 could lead to the development or progression of HCC.

Inverted papilloma of urinary bladder: Is long-term cystoscopic surveillance needed? A single center’s experience

OBJECTIVES

To review all cases of urinary bladder inverted papilloma (IP) in our institution and determine the need for cystoscopic surveillance. IP is an uncommon benign tumor of the urinary tract. Its multiplicity, recurrence, and association with transitional cell carcinoma (TCC) suggest possible malignant potential, leading to conflicting clinical conclusions regarding the need for surveillance.

METHODS

All consecutive patients from January 1991 to December 2004 with IP were included in this study. A single pathologist performed the histologic review. The patients had undergone cystoscopy and ultrasound evaluation of the kidneys every 6 months.

RESULTS

Of the 52 patients, 45 were men and 7 were women. The average age at presentation was 58.9 +/- 11.8 years (range 30 to 79). No patient had a synchronous or previous bladder tumor. The most common complaint was macroscopic hematuria. Ten cases were incidental findings during bladder ultrasonography or cystoscopy. All were solitary tumors, most commonly found at the bladder neck. The average follow-up period was 62 +/- 23 months, with no recurrence. One case of subsequent noninvasive papillary TCC developed 15 months later. The initial histologic findings had revealed cytologic atypia, with suspicious urine cytology findings. On review, it was more compatible with TCC with an inverted pattern.

CONCLUSIONS

Although our cases exhibited benign biologic behavior, the presence of cytologic atypia and suspicious urine cytology require exclusion of TCC with an inverted pattern. Thus, in histologically proven solitary bladder IP with no associated TCC, cystoscopic surveillance may not be necessary.

Gene therapy for clinical transplantation: where do we stand in 2006?

Gene therapy holds a great promise to prevent allograft rejection or to induce transplant tolerance. Many achievements in vector development have allowed the progression of this therapy to become more attainable in clinical transplantation. In this articles, the authors examine the exciting development in various vector technologies that allows this form of therapy to take the central stage of clinical transplantation. Also highlighted are various therapeutic strategies that might ultimately result in the realization of gene-based treatment in clinical transplantation.

Gene therapy for transplantation with viral vectors – how much of the promise has been realised?

Gene therapy holds promise in preventing the development of many diseases. One of the possible applications is the management of organ transplantation. Over the years, advances in vector development have allowed the clinical progression of this form of therapy to become more attainable. Viral vector technology has proved to be better than non-viral vectors at ferrying therapeutic genes to cells. However, many deficiencies in viral vectors hinder the full realisation of gene-based therapy in transplantation. Here, these deficiencies and their ramifications for the future of viral vector development are fully analysed. The authors propose that the slow progress of gene therapy in transplantation may be related to the deficiencies in viral vectors.

Fat necrosis of the breast—A review

Fat necrosis of the breast is a benign condition that most frequently affects peri-menopausal women. It can mimic breast cancer clinically or radiologically. In other cases it can obscure malignant lesions. The core of this review is derived from a MEDLINE database literature search from 1966-2004. Further references were from lateral search. In this paper, we review the pathogenesis and pathology clinical and radiological features of fat necrosis of the breast. The implication of fat necrosis in the management of patients with breast lump is also discussed. Fat necrosis of breast is a complex process. Therefore, a systematic review of this condition will enable surgeons, radiologists and oncologists working in the field of breast disease to understand it better and improve its management.

Expression of indoleamine 2,3-dioxygenase (IDO) by endothelial cells: implications for the control of alloresponses

Indoleamine 2,3-dioxygenase (IDO) is an important enzyme in the regulation of immune responses; cells that express IDO can suppress T-cell responses and promote tolerance. Because of the critical role of endothelial cells in graft rejection, we have investigated the role of IDO expression by vascular endothelial cells and its consequence on immunoregulation. We compared the expression of IDO by primary human umbilical vein endothelial cells (HUVECs), human saphenous vein endothelial cells (HSVECs) and arterially derived endothelial cells using reverse transcriptase PCR, Western blotting and assays for enzymatic activity. In HUVECs IDO is upregulated by incubation with cytokines or in mycoplasma-infected cells. On the other hand HSVECs and arterially derived endothelial cells express little IDO, which is poorly upregulated upon activation (except by mycoplasma). Inhibition of IDO activity improved the ability of HUVECs to stimulate allogeneic T-cell responses. If either HUVECs or HSVECs are transfected with the gene encoding IDO, then they are incapable of stimulating allogeneic T-cell responses and induce anergy in allospecific T cells (which can also act as regulatory cells). The variable expression of IDO in different endothelial cells is important not only in understanding the role of endothelial cells in the regulation of graft rejection, but also as a potential therapeutic strategy.

Rosai-Dorfman disease of the testis: an unusual entity that mimics testicular malignancy

A 47 year old Chinese man with diabetes mellitus and previously treated pulmonary tuberculosis presented with painless right testicular enlargement of 1 month's duration. He underwent an orchidectomy for presumed testicular neoplasm corroborated clinicoradiologically. Histological examination of the testicular mass revealed an inflammatory lesion comprising lymphocytes, plasma cells and sheets of pale staining histiocytes, some containing lymphocytes within their ample cytoplasm, suggestive of emperipolesis. S100 immunohistochemistry stained the histiocytes, while ultrastructural examination confirmed emperipolesis. A diagnosis of Rosai-Dorfman disease was made, an exceedingly rare testicular lesion. Clinicoradiological findings mimicked a neoplasm, while the inflammatory histological appearances with occasionally discerned multinucleated cells raised the possibility of xanthogranulomatous orchitis. Tuberculous orchitis was excluded through negative Ziehl-Neelsen stains and PCR for mycobacterium, while seminoma, which sometimes features a predominant inflammatory component obscuring neoplastic cells, was excluded by absent immunostaining for placental alkaline phosphatase and CD117.

Strategies to improve non-viral vectors – potential applications in clinical transplantation

Prevention of acute rejection has been well controlled with immunosuppressive drugs. However, the long-term control of rejection is less satisfactory and the side effects of chronic usage of these drugs are far from acceptable. Thus, more imaginative options for therapy need to be explored. Gene therapy has potential promise in preserving allografts, preventing rejection and inducing tolerance. Despite this initial promise in many animal models, the translation of gene therapy to the clinical arena has been slow. This may be related in part to the deficiencies in vector development. Existing viral vectors are efficient at transducing allografts, but they induce inflammatory and pathogenic effects. Although the alternative non-viral systems are relatively innocuous, they are less efficient at gene delivery. This review systematically analyses the limitations of non-viral vector technology and the strategies that have been developed to overcome these limitations. Future development of non-viral vectors may have potential application in clinical transplantation.

An unusual cause of granulomatous inflammation: eosinophilic abscess in Langerhans cell histiocytosis

Eosinophilic abscess inciting a granulomatous response has rarely been reported and appears not to have been described in the setting of a neoplasm. In this report, a case is described where a granulomatous response occurred around eosinophilic abscesses in a patient with Langerhans cell histiocytosis, an association which has not previously been documented. On histology, the excised lymph node showed the presence of eosinophilic abscess and necrosis surrounded by granulomas, which in turn were surrounded by Langerhans cells, a feature confirmed on immunohistochemistry. Although rare, this case highlights the importance of careful examination of eosinophilic abscess with granulomatous inflammation in order to exclude an underlying neoplasm.

Function of indoleamine 2,3-dioxygenase in corneal allograft rejection and prolongation of allograft survival by over-expression

Indoleamine 2,3-dioxygenase (IDO) suppresses T cell responses by its action in catabolising tryptophan. It is important in maintenance of immune privilege in the placenta. We investigated the activity of IDO in the cornea, following corneal transplantation and the effect of IDO over-expression in donor corneal endothelium on the survival of corneal allografts. IDO expression was analysed and functional activity was quantified in normal murine cornea and in corneas following transplantation as allografts. Low levels of IDO, at both mRNA and protein levels, was detected in the normal cornea, up-regulated by IFN-gamma and TNF. Expression of IDO in cornea was significantly increased following corneal transplantation. However, inhibition of IDO activity in vivo had no effect on graft survival. Following IDO cDNA transfer, murine corneal endothelial cells expressed functional IDO, which was effective at inhibiting allogeneic T cell proliferation. Over-expression of IDO in donor corneal allografts resulted in prolonged graft survival. While, on one hand, our data indicate that IDO may augment corneal immune privilege, up-regulated IDO activity following cytokine stimulation may serve to inhibit inflammatory cellular responses. While increasing IDO mRNA expression was found in allogeneic corneas at rejection, over-expression in donor cornea was found to significantly extend survival of allografts.

Nuclear morphometry in columnar cell lesions of the breast: is it useful?

AIMS

To evaluate the nuclear morphometric features of breast columnar cell lesions (CCLs) observed on mammotome core biopsies, to determine if there are significant measurable differences between those with atypia and those without. Correlation with follow-up open excision specimens was made.

METHODS

Mammotome core biopsies performed on patients that contained CCLs were derived from the departmental case files. Histological material was reviewed and foci of CCLs demarcated for nuclear morphometric assessment, which was accomplished using an imaging system. Nuclear parameters studied were nuclear area and perimeter, circularity factor and feret's diameter. Statistical analysis used the GraphPad Prism software, with p<0.05 indicating significance.

RESULTS

On examination of core biopsies of 40 patients with CCLs, 8 lesions were benign, 4 showed atypical lobular hyperplasia, 8 showed CCLs with nuclear atypia, 19 disclosed atypical ductal hyperplasia (ADH) and 1 showed ductal carcinoma in situ (DCIS). The nuclear area, perimeter and feret's diameter of CCLs with atypia were significantly greater than those without (p = 0.04, 0.03 and 0.019, respectively), whereas no difference was observed in the circularity factor. Follow-up open excision biopsy specimens in 24 patients showed upgrading to DCIS in 40% of cases diagnosed initially with ADH on core biopsy compared with 20% of CCLs with atypia.

CONCLUSIONS

Nuclear morphometry in CCLs confirms nuclear size as the key parameter in the assessment of nuclear atypia. Whether it can be potentially used as an adjunctive tool depends on the establishment of appropriate cut-offs.

Metaplastic carcinoma of the breast: a clinicopathological review

BACKGROUND

Mammary metaplastic carcinoma encompasses epithelial-only carcinoma (high-grade adenosquamous carcinoma or pure squamous cell carcinoma), biphasic epithelial and sarcomatoid carcinoma and monophasic spindle cell carcinoma.

AIM

To evaluate the clinicopathological features of a large series of 34 metaplastic carcinomas.

METHODS

10 epithelial-only, 14 biphasic and 10 monophasic metaplastic carcinomas were assessed for nuclear grade, hormone receptor status, HER2/neu (cerbB2) oncogene expression, Ki-67 and p53, lymph node status and recurrence on follow-up.

RESULTS

Intermediate to high nuclear grade were assessed in most (33/34) tumours. Oestrogen and progesterone receptors were negative in 8 of 10 epithelial-only, all 14 biphasic, and 9 of 10 monophasic tumours, cerbB2 was negative in 7 of 10 epithelial-only, all 14 biphasic and 8 of 10 monophasic tumours. Ki-67 was found to be positive in 6 of 10 epithelial-only, 6 of 14 biphasic, and 7 of 10 monophasic tumours, whereas p53 was positive in 6 of 10 epithelial-only, 7 of 14 biphasic, and 8 of 10 monophasic tumours. Lymph node metastases were seen in 7 of 7 epithelial-only, 7 of 11 biphasic, and 3 of 7 monophasic tumours. Recurrences were seen in 4 of 7 epithelial-only, 8 of 9 biphasic, and 4 of 9 monophasic tumours.

CONCLUSIONS

All three subtypes of metaplastic carcinoma are known to behave aggressively, and should be differentiated from the low-grade fibromatosis-like metaplastic carcinoma, which does not metastasize. Oncological treatment options may be limited by the frequently negative status of hormonal receptor and cerbB2.

Effect of vectors on human endothelial cell signal transduction: implications for cardiovascular gene therapy

OBJECTIVE

Endothelium is an important target for gene therapy. We have investigated the effect of viral and nonviral vectors on the phenotype and function of endothelial cells (ECs) and developed methods to block any activation caused by these vectors.

METHODS AND RESULTS

Transduction of ECs with viral vectors, including adenovirus, lentiviruses, and Moloney murine leukemia virus, can induce a pro-inflammatory phenotype. This activation was reduced when nonviral vectors were used. We demonstrate that after transduction there is upregulation of dsRNA-triggered antiviral and PI3K/Akt signaling pathway. Blockade of the NFkappaB, PI3-K, or PKR signaling pathways all operated to inhibit partially virally induced activation, and inhibition of both PKR and PI3-K pathways totally blocked EC activation. Furthermore, inhibition of IFN-alpha/beta in addition to PI3-K was effective at preventing EC activation.

CONCLUSIONS

Viral vectors, although efficient at transducing ECs, result in their activation. Blockade of the signaling pathways involved in viral activation may be used to prevent such activation.

2005 Galloway Memorial Lecture: Breast phyllodes tumours--morphology and beyond

OBJECTIVES

The aims of this study were to evaluate the predictive role of morphology in a series of breast phyllodes tumours (PTs) in Asian women, and to determine the utility of immunohistochemical expression of p53 and CD117 in the stromal component.

MATERIALS AND METHODS

Breast PTs, diagnosed between January 1992 and December 2002 at the Department of Pathology, Singapore General Hospital, were classified into benign, borderline and malignant categories. Surgical margins were evaluated as complete or diffusely involved. Patient follow-up was obtained from casenotes and the Singapore Cancer Registry. Tissue microarrays (TMAs) were constructed using the 2-mm punch on the Beecher arrayer. p53 and CD117 immunohistochemistry was applied on 4-microm sections cut from TMA blocks. Immunostaining intensity was graded as 0, 1+, 2+ or 3+, for nil, weak, moderate and strong reactivity. The proportion of stromal cells decorated was assessed. Statistical analysis utilised the software SPSS for windows 11.5. Survival curves were plotted using the Kaplan-Meier method, while multivariate analysis was accomplished using the stepwise Cox proportional hazards model. A P value of <0.05 was considered a significant result. For verification of protein expression results, a pure stromal population derived from laser capture microdissection was subjected to real-time polymerase chain reaction to determine p53 and CD117 mRNA upregulation.

RESULTS

Three hundred thirty-five women diagnosed with PT were aged 16 to 69 years (median, 42 years). Tumour size ranged from 0.9 to 25 cm (median, 4 cm). Histologic classification revealed 250 (74.6%) benign, 54 (16.1%) borderline and 31 (9.3%) malignant PTs. Surgical margins were focally involved in 186 (55.5%) cases, diffusely affected in 9 (2.9%) cases and complete in 139 (41.5%) cases. Stromal cells positively stained ranged from 1% to 80% (mean, 15%; median, 5%) for p53, and 1% to 25% for CD117 (mean, 8%; median, 3%). p53 and CD117 staining was associated with PT grade (P = 0.004, P <0.001). Forty-three (12.8%) women suffered 57 recurrences (mean and median follow-up of 30.3 and 20.4 months respectively). Nine (2.7%) died during follow-up, 7 from malignant disease (mean and median survival duration 37.6 and 23.6 months respectively). Complete margins (P = 0.033) resulted in reduced recurrence risk by 51.7%. Though tumour grade was associated with an increased hazard of 1.63, it was not significant (P = 0.28). Immunoexpression of p53 was not associated with recurrence (P = 0.447), while CD117 was (P = 0.001). Upregulation of p53 and CD117 mRNA was found in cases in which there was protein overexpression.

CONCLUSIONS

Involved surgical margins remain a key prognostic parameter in breast PT. Death from disease occurred in women with malignant PTs at presentation, underscoring the need to manage this group more aggressively. p53 staining can be used to corroborate malignancy in PT. CD117 was predictive of recurrence, and if further validated, its expression can be explored for therapeutic purposes. Preliminary molecular studies verify mRNA upregulation in p53 and CD117 overexpressed cases.

Delivery of oligodeoxynucleotides into human saphenous veins and the adjunct effect of ultrasound and microbubbles

Therapy with naked oligodeoxynucleotides (ODNs, molecular weight: 3000 to 7500) provides an elegant means of modulating gene expression without the problems associated with conventional gene therapy, but the relatively low transfer efficiency on intravascular administration is a limitation to clinical application. Ultrasound, which can be potentiated by microbubbles, shows promise as a method of delivering macromolecules such as plasmid DNA and other transgenes into cells. Since uptake of molecules into cells depends on their molecular weight, it might be expected that the delivery of ODNs, which are relatively small, will be facilitated by ultrasound and microbubbles. In the present study, we delivered ODNs into veins using ultrasound and microbubbles. First, we quantified the uptake of fluorescent-labeled ODNs into intact ex vivo human saphenous veins and isolated smooth muscle cells from the veins, evaluating the effect of ultrasound and microbubbles on uptake. Ultrasound potentiated the delivery of ODN in cells, except at high concentrations. When intact veins were studied, we achieved nuclear localization of fluorescent-labeled ODNs in cells. This increased with increasing concentration and incubation time and was not potentiated by ultrasound, even when microbubbles were used. We then applied a therapeutic ODN (antisense to intercellular adhesion molecule 1, ICAM-1) to vein samples and documented a functional inhibition of gene expression in a sequence-specific manner at the protein level with immunohistochemistry and western blot analysis. Again, no significant difference was seen with adjunct ultrasound. These observations suggest high diffusion of ODNs into human saphenous veins in this ex vivo model, indicating potential applications to inhibition of vascular bypass graft occlusion and other vasculopathies. Although microbubble-ultrasound was of value with cells in culture, it was not beneficial with intact veins.

The evolving role of gene-based treatment in surgery

Background

The completion of the sequencing of the human genome in 2003 marked the dawn of a new era of human biology and medicine. Although these remarkable scientific advances improve the understanding of human biology, the question remains how this rapidly expanding knowledge of functional genomics affects the role of surgeons. This article reviews the potential therapeutic application of gene therapy for various surgical conditions.

Methods

The core of this review was derived from a Medline database literature search.

Results and conclusion

The currently available vectors in the field of gene therapy and their limitations for clinical applications were analysed. The achievements of gene therapy in clinical trials and the future ramifications for surgery were also explored. Whether gene therapy takes a major role in surgical practice will depend greatly on the success of future vector development. Advances in viral vector technology to reduce the inflammatory effect, and improvements in the efficiency of gene delivery using non-viral vector technology, would allow this form of therapy to become more clinically applicable.

Pathological diagnosis of columnar cell lesions of the breast: are there issues of reproducibility?

AIMS

To assess inter/intraobserver variability in the interpretation of a series of digitised images of columnar cell lesions (CCLs) of the breast.

METHODS

After a tutorial on breast CCL, 39 images were presented to seven staff pathologists, who were instructed to categorize the lesions as follows: 0, no columnar cell change (CCC) or ductal carcinoma in situ (DCIS); 1, CCC; 2, columnar cell hyperplasia; 3, CCC with architectural atypia; 4, CCC with cytological atypia; 5, DCIS. Concordance with the tutor's diagnosis and degree of agreement among pathologists for each image were determined. The same set of images was re-presented to the pathologists one week later, their diagnoses collated, and inter/intraobservor reproducibility and level of agreement for individual images analysed.

RESULTS

Diagnostic reproducibility with the tutor ranged from moderate to substantial (kappa values, 0.439-0.697) in the first exercise. At repeat evaluation, intraobserver agreement was fair to perfect (kappa values, 0.271-0.832), whereas concordance with the tutor varied from fair to substantial (kappa values, 0.334-0.669). There was unanimous agreement on more images during the second exercise, mainly because of agreement on the diagnosis of DCIS. The lowest agreement was seen for CCC with cytological atypia.

CONCLUSIONS

Interobserver and intraobserver agreement is good for DCIS, but more effort is needed to improve diagnostic consistency in the category of CCC with cytological atypia. Continued awareness and study of these lesions are necessary to enhance recognition and understanding.

Inhibition of NF-kappa B and oxidative pathways in human dendritic cells by antioxidative vitamins generates regulatory T cells

Dendritic cells (DCs) are central to T cell immunity, and many strategies have been used to manipulate DCs to modify immune responses. We investigated the effects of antioxidants ascorbate (vitamin C) and alpha-tocopherol (vitamin E) on DC phenotype and function. Vitamins C and E are both antioxidants, and concurrent use results in a nonadditive activity. We have demonstrated that DC treated with these antioxidants are resistant to phenotypic and functional changes following stimulation with proinflammatory cytokines. Following treatment, the levels of intracellular oxygen radical species were reduced, and the protein kinase RNA-regulated, eukaryotic translation initiation factor 2alpha, NF-kappaB, protein kinase C, and p38 MAPK pathways could not be activated following inflammatory agent stimulation. We went on to show that allogeneic T cells (including CD4(+)CD45RO, CD4(+)CD45RA, and CD4(+)CD25(-) subsets) were anergized following exposure to vitamin-treated DCs, and secreted higher levels of Th2 cytokines and IL-10 than cells incubated with control DCs. These anergic T cells act as regulatory T cells in a contact-dependent manner that is not dependent on IL-4, IL-5, IL-10, IL-13, and TGF-beta. These data indicate that vitamin C- and E-treated DC might be useful for the induction of tolerance to allo- or autoantigens.

Recurrent prostatic stromal tumour of uncertain malignant potential (STUMP) presenting with urinary retention 6 Years after transurethral resection of prostate (TURP)

CLINICAL PRESENTATION

A 56-year-old Chinese male with previously diagnosed prostatic stromal tumour of uncertain malignant potential (STUMP) presented with urinary retention 6 years after transurethral resection of prostate (TURP).

TREATMENT AND OUTCOME

Cystoscopy showed a papillary tumour of the prostatic urethra causing near-complete obstruction. Repeat TURP was performed. He has been asymptomatic since.

CONCLUSION

There has been fewer than 100 cases of this lesion reported worldwide. Definitive treatment is not well established. Longterm follow-up to monitor progression and possible recurrence is required, and repeat TURP or radical surgery may be necessary.

Tolerant T cells display impaired trafficking ability

Based on our previous observation that anergic T lymphocytes lose their migratory ability in vitro, we have proposed that anergic T cells are retained in the site where they have been generated to exert their regulatory function. In this study we have analyzed T lymphocyte trafficking and motility following the induction of tolerance in vivo. In a model of non-deletional negative vaccination to xenoantigens in which dendritic cells (DC) localize to specific lymphoid sites depending on the route of administration, tolerant T cells remained localized in the lymph nodes colonized by tolerogenic DC, while primed T cells could traffic efficiently. Using an oral tolerance model that enables the 'tracking' of ovalbumin-specific TCR-transgenic T cells, we confirmed that T cells lose the ability to migrate through syngeneic endothelial cell monolayers following tolerance induction in vivo. Finally, we show that tolerant T cells (both in vitro and ex vivo) can inhibit migration of responsive T cells in an antigen-independent manner. Thus, hyporesponsive T cells localize at the site of tolerance induction in vivo, where they exert their anti-inflammatory properties. In physiological terms, this effect is likely to render immunoregulation a more efficient and controllable event.

Creation of tolerogenic human dendritic cells via intracellular CTLA4: a novel strategy with potential in clinical immunosuppression

Activation of T lymphocytes requires the recognition of peptide-major histocompatibility complexes (MHCs) and costimulatory signals provided by antigen-presenting cells (APCs). It has been shown that T-cell activation without costimulation can lead to anergy. In this study, we developed a novel strategy to inhibit expression of B7 molecules (CD80/86) by transfecting APCs with a gene construct encoding a modified cytotoxic T lymphocyte antigen 4 (CTLA4) molecule (CTLA4-KDEL) that is targeted to the endoplasmic reticulum (ER). APCs expressing this construct failed to express CD80/86 on their surface, were unable to stimulate allogeneic and peptide-specific T-cell responses, and induced antigen-specific anergy of the responding T cells. Cells expressing CTLA4-KDEL do not up-regulate the indoleamine 2, 3-dioxygenase enzyme, unlike cells treated with soluble CTLA4-immunoglobin (Ig). This gene-based strategy to knock out surface receptors is an attractive alternative to using immature dendritic cells for preventing transplant rejection and treating of autoimmune diseases.