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Introduction:  Anorectal malformations (ARMs) are rare congenital anomalies that involve the anus, rectum, and oftentimes the genitourinary tract. The management of ARM patients is complex, and many controversies exist. To address this issue, the European Reference Network eUROGEN for rare and complex urogenital conditions aimed to develop comprehensive guidelines for the management of ARM., Methods:  The Dutch Quality Standard for ARM served as the basis for the development of guidelines applicable on a European level. Literature was searched in Medline, Embase, and Cochrane. The ADAPTE method was utilized to incorporate the newest available evidence. A panel of 15 experts from 7 European countries assessed currency, acceptability, and applicability of recommendations. Recommendations from the Dutch Quality Standard were adapted, adopted, or rejected, and recommendations were formed considering current evidence and/or expert consensus., Results:  Prenatal and neonatal diagnostic workup as well as postsurgical follow-up of anorectal, genitourinary tract, and neurologic system were reviewed. Seven new studies were identified. The panel adapted 13 recommendations, adopted 7, and developed 8 de novo. The availability of high-quality evidence was limited, and most recommendations were based on retrospective studies, case series, or expert opinion., Conclusion:  Patients with ARM and their families require highly specialized and comprehensive care from the prenatal period to adulthood. This guideline provides recommendations for a comprehensive diagnostic workup of children with ARM throughout their life that is applicable on a European level., Competing Interests: We would like to disclose that two of the authors of this adaptation report (I.D.B., C.E.J.S.) were also authors of the Dutch Quality Standard. However, it is important to note that neither I.D.B. nor C.E.J.S. has any conflict of interest to declare and they did not advocate for any particular viewpoints or positions in relation to the content of the Dutch Quality Standard. No conflicting interests were declared from the other authors., (Thieme. All rights reserved.)

Introduction:  Being born with an anorectal malformation (ARM) can have profound and lifelong implications for patients and parents. Organization of care and communication between health care providers is an overlooked area of patient care. The European Reference Network eUROGEN for rare and complex urogenital conditions assembled a panel of experts to address these challenges and develop comprehensive guidelines for the management of ARM., Methods:  The Dutch Quality Standard for ARM served as the basis for the development of guidelines. Literature was searched in Medline, Embase, and Cochrane. The ADAPTE method was utilized to incorporate the newest available evidence. A panel of 15 experts from seven European countries assessed currency, acceptability, and applicability of recommendations. Recommendations from the Dutch Quality Standard were adapted, adopted, or rejected and recommendations were formed considering all available evidence, expert consensus, and the European context., Results:  Aspects pertaining to organization of care, patient/parent/health care provider communication, and referral and collaboration between providers caring for ARM patients were assessed. Two new studies were identified. In total, the panel adapted 12 recommendations, adopted 7, and developed 2 de novo. The overall level of newly found evidence was considered low and most recommendations were based on expert opinion., Conclusion:  Collaborative care and organization of care are gaining importance in the field of ARM. This guideline gives practical guidance on how to achieve better communication and collaboration between all involved parties, applicable at the European level., Competing Interests: We would like to disclose that two of the authors of this adaptation report (I.D.B., C.S.) were also authors of the Dutch Quality Standard. However, it is important to note that neither I.D.B. nor C.S. has any conflict of interest to declare and they did not advocate for any particular viewpoints or positions in relation to the content of the Dutch Quality Standard. No conflicting interests were declared from the other authors., (Thieme. All rights reserved.)

Introduction:  Anorectal malformations (ARMs) are rare birth defects affecting the anorectum and oftentimes the genitourinary region. The management of ARM patients is complex and requires highly specialized surgical and medical care. The European Reference Network eUROGEN for rare and complex urogenital conditions aimed to develop comprehensive guidelines for the management of ARM applicable on a European level., Methods:  The Dutch Quality Standard for ARM served as the basis for the development of guidelines. Literature was searched in Medline, Embase, and Cochrane. The ADAPTE method was utilized to incorporate the newest available evidence. A panel of 15 experts from seven European countries assessed currency, acceptability, and applicability of recommendations. Recommendations from the Dutch Quality Standard were adapted, adopted, or rejected and recommendations were formed considering the current evidence, expert opinion, and the European context., Results:  Surgical and medical treatment of ARM, postoperative instructions, toilet training, and management of fecal and urinary incontinence were addressed. Seven new studies were identified. The panel adapted 23 recommendations, adopted 3, and developed 8 de novo. The overall level of newly found evidence was considered low., Conclusion:  Treatment of ARM patients requires a multidisciplinary team and expertise about anatomical and surgical aspects of the disease, as well as long-term follow-up. This guideline offers recommendations for surgical and medical treatment of ARM and associated complications, according to the best available evidence and applicable on a European level., Competing Interests: The authors would like to disclose that two of the authors of this adaptation report (I.D.B., C.S.) were also authors of the Dutch Quality Standard. However, it is important to note that neither I.D.B. nor C.S. has any conflict of interest to declare and they did not advocate for any particular viewpoints or positions in relation to the content of the Dutch Quality Standard. No conflicting interests were declared from the other authors., (Thieme. All rights reserved.)

Introduction:  Anorectal malformations (ARMs) are complex congenital anomalies of the anorectal region, oftentimes also affecting the genitourinary system. Although successful surgical correction can often be achieved in the neonatal period, many children will experience functional problems in the long term. The European Reference Network for rare and complex urogenital conditions (eUROGEN) assembled a panel of experts to address these challenges and develop comprehensive guidelines for the management of ARM., Methods:  The Dutch Quality Standard for ARM served as the foundation for the development of guidelines applicable on a European level. Literature was searched in Medline, Embase, and Cochrane. The ADAPTE method was utilized to incorporate the newest available evidence. A panel of 15 experts from 7 European countries assessed currency, acceptability, and applicability of recommendations. Recommendations from the Dutch Quality Standard were adapted, adopted, or rejected and recommendations were formed considering the current evidence and/or expert consensus., Results:  Lifelong follow-up, integration, and transition of care were assessed. A total of eight new studies were identified. The panel adapted 18 recommendations, adopted 6, and developed 6 de novo. Overall, the level of evidence was considered low., Conclusion:  Successful lifelong follow-up and transition of care require a dedicated team of pediatric and adult specialist and an individually tailored patient-centered approach. This guideline summarizes the best available evidence on follow-up of ARM patients and provides guidance for the development of structured transition programs., Competing Interests: We would like to disclose that two of the authors of this adaptation report (IDB, CEJS) were also authors of the Dutch Quality Standard. However, it is important to note that neither IDB nor CEJS have any conflict of interest to declare and they did not advocate for any particular viewpoints or positions in relation to the content of the Dutch Quality Standard. No conflicting interests were declared from the other authors., (Thieme. All rights reserved.)

Objective: To assess the associations between congenital abnormalities and pediatric malignancies and evaluate the potential underlying molecular basis by collecting information on pediatric patients with cancer and congenital abnormalities., Study Design: Tumeur Et Développement is a national, prospective, and retrospective multicenter study recording data of children with cancer and congenital abnormalities. When feasible, blood and tumoral samples are collected for virtual biobanking., Results: From June 2013 to December 2019, 679 associations between pediatric cancers and congenital abnormalities were recorded. The most represented cancers were central nervous system tumors (n = 139; 20%), leukemia and myelodysplastic syndromes (n = 123; 18.1%), and renal tumors (n = 101; 15%). Congenital abnormalities were not related to any known genetic disorder in 66.5% of cases. In this group, the most common anomaly was intellectual disability (22.3%), followed by musculoskeletal (14.2%) and genitourinary anomalies (12.4%). Intellectual disability was mostly associated with hematologic malignancies. Embryonic tumors (neuroblastoma, Wilms tumor, and rhabdomyosarcoma) were associated with consistent abnormalities, sometimes with a close anatomical neighborhood between the abnormality and the neoplasm., Conclusions: In the first Tumeur Et Développement analysis, 3 major themes have been identified: (1) germline mutations with or without known cancer predisposition, (2) postzygotic events responsible for genomic mosaicism, (3) coincidental associations. New pathways involved in cancer development need to be investigated to improve our understanding of childhood cancers., Competing Interests: Declaration of Competing Interest The study was supported by grant from the Programme Hospitalier de Recherche Clinique (PHRC-N 2011). The authors have no conflicts of interest to disclose., (Copyright © 2023 Elsevier Inc. All rights reserved.)

Objectives: The present study aimed to assess long-term functional outcomes of children with anorectal malformations (ARMs) across a network of expert centers in France., Methods: Retrospective cross-sectional study of patients ages 6-30 years that had been surgically treated for ARM. Patient and ARM characteristics (eg, level, surgical approach) and functional outcomes were assessed in the different age groups., Results: Among 367 patients, there were 155 females (42.2%) and 212 males (57.8%), 188 (51.2%) cases with, and 179 (48.8%) higher forms without, perineal fistula. Univariate and multivariate statistical analyses with logistic regression showed correlation between the level of the rectal blind pouch and voluntary bowel movements (odds ratio [OR] = 1.84 [1.31-2.57], P < 0.001), or soiling (OR = 1.72 [1.31-2.25], P < 0.001), which was also associated with the inability to discriminate between stool and gas (OR = 2.45 [1.28-4.67], P = 0.007) and the presence of constipation (OR = 2.97 [1.74-5.08], P < 0.001). Risk factors for constipation were sacral abnormalities [OR = 2.26 [1.23-4.25], P = 0.01) and surgical procedures without an abdominal approach (OR = 2.98 [1.29-6.87], P = 0.01). Only the holding of voluntary bowel movements and soiling rates improved with age., Conclusion: This cross-sectional study confirms a strong association between anatomical status and functional outcomes in patients surgically treated for ARM. It specifically highlights the need for long-term follow-up of all patients to help them with supportive care., Competing Interests: The authors report no conflicts of interest., (Copyright © 2022 by European Society for Pediatric Gastroenterology, Hepatology, and Nutrition and North American Society for Pediatric Gastroenterology, Hepatology, and Nutrition.)

BackgroundChildren have a low rate of COVID-19 and secondary severe multisystem inflammatory syndrome (MIS) but present a high prevalence of symptomatic seasonal coronavirus infections.AimWe tested if prior infections by seasonal coronaviruses (HCoV) NL63, HKU1, 229E or OC43 as assessed by serology, provide cross-protective immunity against SARS-CoV-2 infection.MethodsWe set a cross-sectional observational multicentric study in pauci- or asymptomatic children hospitalised in Paris during the first wave for reasons other than COVID (hospitalised children (HOS), n = 739) plus children presenting with MIS (n = 36). SARS-CoV-2 antibodies directed against the nucleoprotein (N) and S1 and S2 domains of the spike (S) proteins were monitored by an in-house luciferase immunoprecipitation system assay. We randomly selected 69 SARS-CoV-2-seropositive patients (including 15 with MIS) and 115 matched SARS-CoV-2-seronegative patients (controls (CTL)). We measured antibodies against SARS-CoV-2 and HCoV as evidence for prior corresponding infections and assessed if SARS-CoV-2 prevalence of infection and levels of antibody responses were shaped by prior seasonal coronavirus infections.ResultsPrevalence of HCoV infections were similar in HOS, MIS and CTL groups. Antibody levels against HCoV were not significantly different in the three groups and were not related to the level of SARS-CoV-2 antibodies in the HOS and MIS groups. SARS-CoV-2 antibody profiles were different between HOS and MIS children.ConclusionPrior infection by seasonal coronaviruses, as assessed by serology, does not interfere with SARS-CoV-2 infection and related MIS in children.

Anorectal malformation (ARM) is the most common symptom in VACTERL syndrome (vertebral, anal, cardiac, tracheo-esophageal fistula, renal, and limb anomalies). The association of ARM and spinal dysraphisms (DYS) is well documented. We aim to better evaluate children with VACTERL association and ARM, considering the presence or not of DYS. Between 2000 and 2015, 279 children with VACTERL associations were identified in Necker Children's Hospital, Paris. We identified 61 VACTERL children (22%) with ARM. A total of 52 VACTERL children with ARM were included. DYS were identified in 36/52 of cases (69.2%). A total of 33 (63.5%) VACTERL children presented with sphincterial dysfunction. We constated that 28/33 (84.8%) of them had DYS + (p < 0.0001). More children in ARM (DYS +) subgroup are presenting with initial urinary sphincter dysfunction (58 vs 19%, p < 0.009) than ARM (DYS -). We identified 29 lipoma filum in our series, which were not statistically associated with urinary disorders (p = 0.143).Conclusion: We propose to refine the definition of VACTERL association, by adding S as Spinal defect to include it as an integral part of this syndrome, resulting in a novel acronym V.A.C.TE.R.L.S.What is Known:• The VACTERL association: congenital anomalies of the bony vertebral column (V), anorectal malformation (A), congenital cardiopathy (C), tracheo-esophageal defects (TE), renal and urinary tract anomalies (R), and limb malformations (L).• VACTERL children needs a complete appraisal, as early as possible, to adopt the most appropriate therapeutic management.What is New:• Include spine dysraphism (DYS) as a part of this syndrome, resulting in a novel acronym V.A.C.TE.R.L.S.• The significant correlation between VACTERL/DYS and urinary dysfunction requires to investigate the spine cord prenatally.

Introduction:  The diagnosis of anorectal malformations (ARMs) is made at birth by perineal examination of the newborn, yet small series reported late diagnosis in almost 13%. No large series to date have looked into the magnitude of missed ARM cases in the neonatal period across Europe. This study aimed to define the rate of missed ARM at birth across four United Kingdom and European Union centers., Materials and Methods:  All ARM cases treated at two United Kingdom tertiary centers in the past 15 years were compared with two tertiary European centers. Demographic and relevant clinical data were collected. Late diagnosis was defined as any diagnosis made after discharge from the birth unit. Factors associated with late diagnosis were explored with descriptive statistics., Results:  Across the four centers, 117/1,350, 8.7% were sent home from the birth unit without recognizing the anorectal anomaly. Missed cases showed a slight female predominance (1.3:1), and the majority (113/117, 96.5%) were of the low anomaly with a fistula to the perineum. The rate of missed ARM cases was significantly higher in the United Kingdom centers combined (74/415, 17.8%) compared with those in the European Union (43/935, 4.6%) ( p  < 0.00001), and this was independent of individual center and year of birth., Conclusion:  Significant variation exists between the United Kingdom and other European countries in the detection of ARM at birth. We recommend raising the awareness of accurate perineal examination at the time of newborn physical examination. We feel this highlights an urgent need for a national initiative to assess and address the timely diagnosis of ARM in the United Kingdom., Competing Interests: None declared., (Georg Thieme Verlag KG Stuttgart · New York.)

Background: Since 2009 in France, the Peristeen® transanal irrigation (TAI) device has represented an alternative treatment of faecal incontinence (FI)., Objective: The primary objective of this study was to assess the mid-term adherence to TAI in paediatric patients. The secondary objective was to identify factors determining TAI continuation., Methods: This observational study conducted in 5 French paediatric centres prospectively reviewed from March to May 2012 all children educated in TAI for at least 9months., Results: We included 149 children (mean [SD] age 10.6 [4.1] years) educated in TAI. Children mainly had neurogenic disorders (52.3%) or congenital malformations (30.9%). The main symptoms motivating TAI initiation were recurring faecaloma (59.7%) and daily FI (65.1%). At last follow-up (mean 14 [7.4] months), 129 (86.6%) children continued the TAI procedure, independent of pathology or age. The main motivation was resolution of FI and/or constipation (77.3%). In total, 107 (82.9%) children fulfilled the initial therapeutic contract established with their healthcare professional before TAI initiation was met. Twenty children had stopped the TAI when they answered the questionnaire, at a mean duration of 16 (8.4) months. The reasons were mainly "lack of motivation" (45%), "poor tolerance" (35%), "difficulties" performing the procedure (35%) and "inefficacy" (30%). Factors related to continuation were performing at least one TAI procedure under a nurse's supervision during the initial training and prescribing TAI at a daily frequency (P=0.014 and P=0.04). Continuing constipation treatment after the training session was a factor in discontinuation (P=0.024)., Conclusion: This study reports a very high mid-term adherence to TAI in a paediatric cohort, provided that the training is pragmatic, personalized and repeated., (Copyright © 2019 Elsevier Masson SAS. All rights reserved.)

Background: Hirschsprung disease is a rare congenital disease typically requiring surgical treatment during childhood. Quality of life and social condition at adult age can be impaired by disease-specific sequelae., Objective: This study aimed to assess the quality of life and social outcome of adult patients operated on for Hirschsprung disease during childhood., Design: Patients operated on for Hirschsprung disease during childhood were identified and specific questionnaires were sent to them., Settings: Data from 2 referral centers were used., Patients: Patients who completed the questionnaires regarding quality of life and social condition were included., Main Outcome Measures: The Hirschsprung's Disease and Anorectal Malformations Quality of Life disease-specific questionnaire (8 dimensions explored; each scored from 0 to 100 maximum score) and a sociodemographic questionnaire were sent to identified patients. Sociodemographic data were compared with those of the French general population., Results: Thirty-four patients had Hirschsprung disease (men, 76%; mean age, 32 years) were included in the study. Mean total Hirschsprung's Disease and Anorectal Malformations Quality of Life score was 611 of 800 (maximum score 800). The 2 most impaired dimensions were "physical symptoms" and "diarrhea" (62.9/100 and 73.6/100). Fecal continence was only marginally affected (mean score, 89/100). Patients with Hirschsprung disease achieved better educational levels than the French general population. Parental and marital status did not differ between the 2 groups., Limitations: This study had the limitations inherent to a retrospective study., Conclusion: The quality of life of adult patients with Hirschsprung disease sequelae is marginally impaired in this study. Despite the consequences of this congenital abnormality, the condition eventually achieved can be considered as satisfactory. See Video Abstract at http://links.lww.com/DCR/A917.

The estimated prevalence of fetal caudal dysgenesis is 1 per 100,000 births. The functional prognosis of sacral agenesis is dominated by the large spectrum of associated caudal malformations. Except for cases associated with hydrocephalus secondary to open spinal dysraphism or chromosomal anomalies, association with mental deficiency is rare. We propose a systematic prenatal approach to cases of fetal sacral agenesis based on 9 etiologic items: clinical context, type of sacral dysgenesis, associated spinal cord malformations, mobility of lower limbs, investigation of the presacral region, analysis of the gastrointestinal tract, analysis of the genitourinary tract, associated vertebral defects, and cytogenetic analysis., (© 2018 by the American Institute of Ultrasound in Medicine.)

Objectives: To develop the first consensus to standardize the management of patients with Anorectal Malformations (ARMs) transitioning from childhood to adulthood., Methods: A dedicated task force of experts performed an extensive literature review and multiple meetings to define the most important aspects of transition of care. The findings were discussed with all ARM-net consortium members and a set of practical recommendations agreed upon at the annual meeting in 2016., Result: We defined seven domains that are essential to provide an effective and practical transition process. Within each domain we have developed a set of key recommendations that are important to be considered for ARM patients entering the age of transition., Conclusions: It is crucial that transition begins at an early age with regular and well-structured follow-up. Cooperation with a selected multidisciplinary team of pediatric and adult practitioners is required to prepare patients and families for effective transition to adult care and to reduce long term morbidity., Type of Study: Review/Consensus paper., Level of Evidence: III., (Copyright © 2017 Elsevier Inc. All rights reserved.)

Background: There is no precise prenatal indicator to refine an accurate prognosis in case of sacral agenesis and to define the diagnostic approach and outcome criteria in case of fetal sacral agenesis using 3 characteristics of the conus medullaris (CM): its position, its appearance, and associated spinal abnormalities., Methods: Ten cases of prenatally diagnosed sacral agenesis were included between 1995 and 2014 after collating ultrasound findings and prenatal computed tomography data., Results: Two cases of total sacral agenesis and 8 of partial agenesis were included. There were 1 or more spinal abnormalities in 8/10 cases: 6 lipomas, 4 low-lying tethered cords, 2 diastematomyelias, and 1 syringomyelia. Three situations were distinguished: sacral agenesis with low-lying tethered cord, sacral agenesis with a truncated CM, and sacral agenesis with CM in place. If the sacral agenesis is isolated, a lipoma should be sought. Lipomas of the filum have a good prognosis, whereas lipomas of the CM cause neurological deficits in 1/3 of cases. When there is a low-lying tethered cord, a diastematomyelia or a syringomyelia may be associated. In truncated CM, there may be a severe form suggestive of caudal regression syndrome. Serious ultrasound signs are immobility of the lower limbs, talipes equinovarus, impaired bladder emptying, and dilatation of the upper urinary tract., Conclusion: A precise description of the morphology of the CM, its position, and associated spinal malformations are important in defining the neurological, urinary, gastrointestinal, and motor functions prognosis in cases of fetal sacral agenesis., (© 2016 S. Karger AG, Basel.)

Background: Pediatric surgeons and patient organisations agree that fewer centers for anorectal malformations with larger patient numbers are essential to reach better treatment. The European Union transacts a political process which aims to realize such centers of expertise for a multitude of rare diseases. All the centers on a specific rare disease should constitute an ERN on that disease. ARM-Net members in different countries report on first experiences with the implementation of national directives, identifying opportunities and risks of this process., Methods: Relevant details from the official European legislation were analyzed. A survey among the pediatric surgeons of the multidisciplinary ARM-Net consortium about national implementation was conducted., Results: European legislation calls for multidisciplinary centers treating children with rare diseases, and proposes a multitude of quality criteria. The member states are called to allocate sufficient funding and to execute robust governance and oversight, applying clear methods for evaluation. Participation of the patient organisations is mandatory. The national implementations all over Europe differ a lot in respect of extent and timeframe., Conclusions: Establishing Centers of Expertise and a ERN for anorectal malformations offers great opportunities for patient care and research. Pediatric surgeons should be actively engaged in this process.

Anorectal malformations (ARM) are the result of an abnormal development of the terminal part of the digestive tract interesting anus and/or rectum that occur early between the sixth and tenth week of embryonic development. They carry a malformation spectrum of severity depending on the level of disruption of the anorectal canal and of the associated caudal malformations (sacrum and spine). ARM are associated in over half the cases with other malformations that can be integrated in some cases in known syndromes. If surgical treatment to restore anatomy as normal as possible is indispensable, post-operative care is essential for these patients whose defecation mechanisms are altered, to reach if not continence, at least a socially acceptable cleanliness., (Copyright © 2013 Elsevier Masson SAS. All rights reserved.)

Aim: The impact of anorectal malformation (ARM) on bowel function and social, educational and occupational end-points was investigated in adult patients entered on a national database., Method: Data from a national database of adult patients operated on between 1962 and 1999 for ARM were analysed. The database Malformations Ano-rectales et Pelviennes rares (MAREP) was part of a common information system, CEMARA, on rare congenital disorders. A self-administered questionnaire regarding bowel function, academic qualifications, employment and family status was mailed to patients. The type of ARM, subsequent follow-up and management including surgical interventions were retrospectively retrieved from medical records., Results: Of 210 adult patients on the registry since 2008, 68 were included in this study. Only three (8.5%) had had regular follow-up. All reported some disturbance in bowel function. The fertility rate of 1.5 children per woman did not differ from the general population., Conclusion: Anorectal malformation ARM often leads to suboptimal bowel function in adulthood. This has an impact on social integration., (Colorectal Disease © 2013 The Association of Coloproctology of Great Britain and Ireland.)

Feingold syndrome (FS) is a syndromic microcephaly entity for which MYCN is the major disease-causing gene. We studied the expression pattern of MYCN at different stages of human embryonic development and collected a series of 17 FS and 12 isolated oesophageal atresia (IOA) cases. An MYCN gene deletion/mutation was identified in 47% of FS cases exclusively. We hypothesized that mutations or deletions of highly conserved non-coding elements (HCNEs) at the MYCN locus could lead to its misregulation and thereby to FS and/or IOA. We subsequently sequenced five HCNEs at the MYCN locus and designed a high-density tiling path comparative genomic hybridization array of 3.3 Mb at the MYCN locus. We found no mutations or deletions in this region, supporting the hypothesis of genetic heterogeneity in FS.

We report the case of a 29-day-old baby girl in whom Escherichia coli meningitis led to the diagnosis of Currarino syndrome (CS) (OMIM 176450), an autosomal-dominant genetic disorder associated with sacral agenesis, anorectal malformation, presacral masses and spinal cord malformations. Her condition improved with antibiotics and early surgical treatment. A familial study identified other genetically related individuals with similar symptoms.

Background: Anti-LFA-1 (CD11a) antibody increases allograft survival and/or induces tolerance in murine models, but its mechanisms of action remain to be elucidated., Methods: Rag-2-/- H-2b recipient mice, bearing a transgenic T-cell receptor specific for the male antigen HY presented by MHC class II molecule, were transplanted with a C57BL/6 (H-2b) male heart with or without administration of anti-LFA-1 antibody from days -1 to 9., Results: Treatment prevented the transient episode of acute graft rejection observed in nontreated mice and maintained a naive phenotype and proliferative characteristics comparable to that of naive transgenic lymphocytes on day 7 during treatment, with decreased IFN-gamma mRNA and increased IL-4 mRNA. On day 14, phenotype and proliferative response of lymphocytes in treated mice was comparable to those of untreated animals. Furthermore, treatment did not interfere with the generation of CD4+Vbeta6+CD25+ (Foxp3) cells that were observed in long-term nontreated tolerant mice., Conclusions: This in vivo model demonstrates that anti-LFA-1 treatment induced a transient blockade of antigen recognition, which inhibited and postponed induction of signal 1 via the TCR and decreased the intensity of the Th1 response. Importantly, LFA-1 blockade did not disturb spontaneous generation of regulatory mechanism. This treatment would be compatible in clinical settings with other therapeutics inducing regulatory mechanisms.