The importance of non-technical performance for teams managing postpartum haemorrhage: video review of 99 obstetric teams.

OBJECTIVE: Little is known about how teams' non-technical performance influences clinical performance in obstetric emergencies such as postpartum haemorrhage. DESIGN: Video review - observational study. SETTING: A university hospital (5000 deliveries) and a regional hospital (2000 deliveries) in Denmark. POPULATION: Obstetric teams managing real-life postpartum haemorrhage. METHODS: We systematically assessed 99 video recordings of obstetric teams managing real-life major postpartum haemorrhage. Exposure was the non-technical score (AOTP); outcomes were the clinical performance score (TeamOBS) and the delayed transfer to the operating theatre (defined as blood loss >1500 ml in the delivery room). RESULTS: Teams with an excellent non-technical score performed significantly better than teams with a poor non-technical score: 83.7 versus 0.3% chance of a high clinical performance score (P < 0.001), 0.2 versus 80% risk of a low clinical performance score (P < 0.001), and 3.5 versus 31.7% risk of delayed transfer to the operating theatre (P = 0.008). The results remained robust when adjusting for potential confounders such as bleeding velocity, aetiology, time of day, team size, and hospital. The specific non-technical skills associated with high clinical performance were vigilance, role assignment, problem-solving, management of disruptive behavior, and leadership. Communication with the patient and closing the loop were of minor importance. All performance assessments showed good reliability: the intraclass correlation was 0.97 (95% CI 0.96-0.98) for the non-technical score and 0.84 (95% CI 0.76-0.89) for the clinical performance score. CONCLUSION: Video review offers a new method and new perspectives for research in obstetric teams to identify how teams become effective and safe; the skills identified in this study can be included in future obstetric training programmes. TWEETABLE ABSTRACT: Non-technical performance is important for teams managing postpartum haemorrhage; video review of 99 obstetric teams.

Cross-sectional increase of adherence to multidisciplinary tumor board decisions.

BACKGROUND: Cancer research has made great progress in the recent years. With the increasing number of options in diagnosis and therapy the implementation of tumorboards (TUBs) has become standard procedure in the treatment of cancer patients. Adherence tests on tumor board decisions are intended to enable quality assurance and enhancement for work in tumor boards in order to continuously optimize treatment options for cancer patients. METHODS: Subject of this study was the adherence of the recommendations made in three of 14 tumorboards, which take place weekly in the Center for Integrated Oncology (CIO) at the University Hospital Bonn. In total, therapy recommendations of 3815 patient cases were checked on their implementation. A classification into four groups has been made according to the degree of implementation. A second classification followed regarding the reasons for differences between the recommendation and the therapy which the patient actually received. RESULTS: The study showed that 80.1% of all recommendations in the three TUBs were implemented. 8.3% of all recommendations showed a deviance. Most important reasons for the deviances were patient wish (36.5%), patient death (26%) and doctoral decision, due to the patient's comorbidities or side effects of the treatment (24.1%).Interestingly, deviance in all three tumor boards in total significantly decreased over time. CONCLUSIONS: Aim of the study was to clarify the use of tumor boards and find approaches to make them more efficient. Based on the results efficiency might be optimized by increased consideration of patients` preferences, improved presentation of patient-related data, more detailed documentation and further structuring of the tumor board meetings.

Implementation and Benefit Evaluation of Recommendations for Patient Safety in Ambulatory Surgical Care.

Objective: The aim of this study was to evaluate the degree of implementation of recommendations for patient safety in ambulatory surgical care and their benefit as perceived by surgeons in the ambulatory sector. Based on 2 practice recommendations issued by the Association of Statutory Health Insurance Physicians in Westphalia-Lippe, recommendations were formulated specifically for ambulatory surgery and distributed in 2013 to all physicians licensed to conduct ambulatory surgery in Westphalia-Lippe. Methods: We conducted a written survey covering all safety measures addressed by the 2 practice recommendations and assessed the degree of implementation and the perceived benefit for each of these measures as well as the strengths of the recommendations and the challenges of implementing them. The survey was distributed in late 2014 to 2 454 surgeons in the ambulatory setting. The survey period was 7 weeks. The analysis of the quantitative data was mainly descriptive and we conducted thematic summaries of free text answers to open-ended questions. Results: The participation rate was 17% (n=405). The recommendations were known to 86% of the respondents. The majority of recommended safety measures had been implemented systemically in more than 50% of the participating institutions. An increased interprofessional awareness of patient safety measurements was reported as the main impact of the recommendations. Respondents indicated further need for information and practice recommendations concerning the following topics: risk and error management, implementation of the Medical Devices Act, hygiene in medical practice and processing of instruments. Conclusion: This study highlights the valuable contribution practice recommendations can make to patient safety improvement in ambulatory surgical care. Their dissemination to other regions as well as to other ambulatory care settings such as family practice can therefore be recommended.

Team performance during vacuum-assisted vaginal delivery: video review of obstetric multidisciplinary teams.

Introduction: Vacuum extraction is generally considered an operator-dependent task, with most attention directed toward the obstetrician's technical abilities (1-3). Little is known about the effect of the team and non-technical skills on clinical outcomes in vacuum-assisted delivery. This study aimed to investigate whether the non-technical skills of obstetricians were correlated with their level of clinical performance via the analysis of video recordings of teams conducting actual vacuum extractions. Methods: We installed between two or three video cameras in each delivery room at Aarhus University Hospital and Horsens Regional Hospital and obtained 60 videos of teams managing vacuum extraction. Appropriate consent was obtained. Two raters carefully reviewed the videos and assessed the teams' non-technical skills using the Assessment of Obstetric Team Performance (AOTP) checklist, rating all items on a Likert scale score from 1 to 5 (1 = poor; 3 = average; and 5 = excellent). This resulted in a total score ranging from 18 to 90. Two different raters independently assessed the teams' clinical performance (adherence to clinical guidelines) using the TeamOBS-Vacuum-Assisted Delivery (VAD) checklist, rating each item (0 = not done, 1 = done incorrectly; and 2 = done correctly). This resulted in a total score with the following ranges (low clinical performance: 0-59; average: 60-84; and high: 85-100). Interrater agreement was analyzed using intraclass correlation (ICC), and the risk of high or low clinical performance was analyzed on a logit scale to meet the assumption of normality. Results: Teams that received excellent non-technical scores had an 81% probability of achieving high clinical performance, whereas this probability was only 12% among teams with average non-technical scores (p < 0.001). Teams with a high clinical performance often had excellent behavior in the non-technical items of "team interaction," "anticipation," "avoidance fixation," and "focused communication." Teams with a low or average clinical performance often neglected to consider analgesia, had delayed abandonment of the attempted vaginal delivery and insufficient use of appropriate fetal monitoring. Interrater reliability was high for both rater-teams, with an ICC for the non-technical skills of 0.83 (95% confidence interval [CI]: 0.71-0.88) and 0.84 for the clinical performance (95% CI: 0.74-0.90). Conclusion: Although assisted vaginal delivery by vacuum extraction is generally considered to be an operator-dependent task, our findings suggest that teamwork and effective team interaction play crucial roles in achieving high clinical performance. Teamwork helped the consultant anticipate the next step, avoid fixation, ensure adequate analgesia, and maintain thorough fetal monitoring during delivery.

Do team processes really have an effect on clinical performance? A systematic literature review.

There is a growing literature on the relationship between team processes and clinical performance. The purpose of this review is to summarize these articles and examine the impact of team process behaviours on clinical performance. We conducted a literature search in five major databases. Inclusion criteria were: English peer-reviewed papers published between January 2001 and May 2012, which showed or tried to show (i) a statistical relationship of a team process variable and clinical performance or (ii) an improvement of a performance variable through a team process intervention. Study quality was assessed using predefined quality indicators. For every study, we calculated the relevant effect sizes. We included 28 studies in the review, seven of which were intervention studies. Every study reported at least one significant relationship between team processes or an intervention and performance. Also, some non-significant effects were reported. Most of the reported effect sizes were large or medium. The study quality ranged from medium to high. The studies are highly diverse regarding the specific team process behaviours investigated and also regarding the methods used. However, they suggest that team process behaviours do influence clinical performance and that training results in increased performance. Future research should rely on existing theoretical frameworks, valid, and reliable methods to assess processes such as teamwork or coordination and focus on the development of adequate tools to assess process performance, linking them with outcomes in the clinical setting.

Adaptation in anaesthesia team coordination in response to a simulated critical event and its relationship to clinical performance.

BACKGROUND: Recent studies in anaesthesia and intensive care indicate that a team's ability to adapt its coordination activities to changing situational demands is crucial for effective teamwork and thus, safe patient care. This study addresses the relationship between adaptation of team coordination and markers of clinical performance in response to a critical event, particularly regarding which types of coordination activities are used and which team member engages in those coordination activities. METHODS: Video recordings of 15 two-person anaesthesia teams (anaesthesia trainee plus anaesthesia nurse) performing a simulated induction of general anaesthesia were coded, using a structured observation system for coordination activities. The simulation involved a critical event-asystole during laryngoscopy. Clinical performance was assessed using two separate reaction times related to the critical event. RESULTS: Analyses of variance revealed a significant effect of the critical event on team coordination: after the occurrence of the asystole, team members adapted their coordination activities by spending more time on information management-a specific type of coordination activity (F(1,28)=15.17, P=0.001). No significant effect was found for task management. The increase in information management was related to faster decisions regarding how to respond to the critical event, but only for trainees and not for nurses. CONCLUSIONS: Our findings support the claim that adaptation of coordination activities is related to improved team performance in healthcare. Moreover, adaptation and its relationship to team performance were found to vary with regard to type of coordination activities and team member.

Evolution of antibody structure during the immune response. The differentiative potential of a single B lymphocyte.

Changes in the structure and function of antibodies occur during the course of an immune response due to variable (V) region gene somatic mutation and isotype switch recombination. While the end products of both these processes are now well documented, their mechanisms, timing, and regulation during clonal expansion remain unclear. Here I describe the characterization of antibodies expressed by a large number of hybridomas derived from single B cell clones at an intermediate stage of an immune response. These data provide new insights into the mechanism, relative timing, and potential of V gene mutation and isotype switching. The data suggest that somatic mutation and isotype switching are completely independent processes that may, but need not, occur simultaneously during clonal expansion. In addition, the results of this analysis demonstrate that individual B cell clones are far more efficient than previously imagined at generating and fixing particular V region somatic mutations that result in increased affinity for the eliciting epitope. Models to account for this high efficiency are discussed. Taken together with previous data, the results of this analysis also suggest that the "somatic evolution" of V region structure to a single epitope takes place in two stages; the first in which particular mutations are sustained and fixed by antigen selection in the CDR regions of the V region genes expressed in a clone over a short period of clonal expansion, and the second in which these selected CDR mutations are maintained in the growing clone, deleterious mutations are lost, and selectively neutral mutations accumulate throughout the length of V genes over long periods of clonal expansion.

Influence of the macromolecular form of a B cell epitope on the expression of antibody variable and constant region structure.

We investigated the influence of the macromolecular form of an epitope on the structure of antibody variable and constant regions expressed by the B cell population participating in an immune response to that epitope. Hybridomas were constructed from strain A/J mice undergoing either primary or secondary immune responses to p-azophenylarsonate conjugated to Brucella abortus (Ars-Bruc). We determined the sequences of the V genes expressed by hybridomas selected on the basis of expression of a single VH gene segment known to encode a large family of anti-Ars antibodies. These sequences were compared with the sequences of V genes expressed by a previously characterized panel of hybridomas isolated in the same way during the primary and secondary responses of A/J mice to Ars-KLH. The repertoire of Ars-specific V domains expressed among primary and secondary hybridomas elicited with these two forms of Ars were similar, as were the differences between primary and secondary V region somatic mutational alteration and affinity for Ars. In contrast, predominant expression of IgG2 anti-Ars antibodies was elicited in the secondary Ars-Bruc response, whereas secondary anti-Ars antibodies elicited with Ars-KLH are predominantly IgG1. Thus, differences in the macromolecular form of Ars clearly influence the isotypic profile of the anti-Ars response, but the expression, diversification, and selection of V domains elicited with this hapten are not greatly affected by such differences. Our results suggest that while isotype regulation is highly perceptive of the macromolecular form of a B cell epitope, V region regulation is primarily influenced by the molecular structure of that epitope.

The transcriptional promoter regulates hypermutation of the antibody heavy chain locus.

A somatic process introduces mutations into antibody variable (V) region genes at a high rate in many vertebrates, and is a major source of antibody diversity. The mechanism of this hypermutation process remains enigmatic, although retrospective studies and transgenic experiments have recently suggested a role for transcriptional regulatory elements. Here, we demonstrate that mouse heavy (H) chain loci in which the natural VH promoter has been replaced by a heterologous promoter undergo hypermutation. However, while the distribution of mutation in such loci appears normal, the frequency of mutation does not. Conversely, moving the VH promoter 750 bp upstream of its normal location results in a commensurate change in the site specificity of hypermutation in H chain loci, and the foreign DNA inserted into the VH leader intron to produce this promoter displacement is hypermutated in a manner indistinguishable from natural Ig DNA. These data establish a direct mechanistic link between the IgH transcription and hypermutation processes.

Somatic generation of hybrid antibody H chain genes in transgenic mice via interchromosomal gene conversion.

We have constructed lines of mice with transgenes containing an antibody heavy (H) chain variable region (VHDJH) gene and various amounts of natural immunoglobulin (Ig) and plasmid flanking DNA. In these lines, recombination of the transgene and the endogenous Igh locus takes place in B cells, leading to the expression of functional H chains partially encoded by the transgenic VHDJH gene. Here, we demonstrate that the transgenic VHDJH gene, and various amounts of flanking sequence are recombined with Igh locus DNA via interchromosomal gene conversion. The structures of the resulting "hybrid" transgene-Igh H chain loci are consistent with the 3' end of the conversion occurring in regions of sequence identity, and the 5' end taking place between regions of little or no homology. This mode of antibody transgene recombination with the Igh locus is fundamentally different from the previously reported "trans H chain class switching" that results in reciprocal translocations. In contrast, this recombination resembles events previously observed in mammalian tissue culture cells between adjacent homologous chromosomal sequences, or transfected DNA and a homologous chromosomal target. Our data indicate that this recombination takes place at a low frequency, and that the frequency is influenced by both the length and extent of homology between the transgene and the Igh locus, but is not greatly affected by transgene copy number. This recombination pathway provides a novel approach for the subtle alteration of the clonal composition of the mouse B cell compartment in vivo using VH genes with defined structures and functions.

Random mutagenesis of two complementarity determining region amino acids yields an unexpectedly high frequency of antibodies with increased affinity for both cognate antigen and autoantigen.

To gain insight into the mechanism and limitations of antibody affinity maturation leading to memory B cell formation, we generated a phage display library of random mutants at heavy chain variable (V) complementarity determining region 2 positions 58 and 59 of an anti-p-azophenylarsonate (Ars) Fab. Single amino acid substitutions at these positions resulting from somatic hypermutation are recurrent products of affinity maturation in vivo. Most of the ex vivo mutants retained specificity for Ars. Among the many mutants displaying high Ars-binding activity, only one contained a position 58 and 59 amino acid combination that has been previously observed among the monoclonal antibodies (mAbs) derived from Ars-immunized mice. Affinity measurements on 14 of the ex vivo mutants with high Ars-binding activity showed that 11 had higher intrinsic affinities for Ars that the wild-type V region. However, nine of these Fabs also bound strongly to denatured DNA, a property neither displayed by the wild-type V region nor observed among the mutants characteristic of in vivo affinity maturation. These data suggest that ex vivo enhancement of mAb affinity via site-directed and random mutagenesis approaches may often lead to a reduction in antibody specificity that could complicate the use of the resulting mAbs for diagnostic and therapeutic applications. Moreover, the data are compatible with a hypothesis proposing that increased specificity for antigen, rather than affinity per se, is the driving force for formation of the memory B cell compartment.

Altering the antibody repertoire via transgene homologous recombination: evidence for global and clone-autonomous regulation of antigen-driven B cell differentiation.

Antibody VH transgenes containing small amounts of natural 5' and 3' flanking DNA undergo nonreciprocal homologous recombination with the endogenous Igh locus in B cells. The resulting "hybrid" heavy chain loci are generated at a low frequency but are fully functional, undergoing somatic hypermutation and isotype class switching. We have used this recombination pathway to introduce a somatically mutated variable (V) region with an unusually high affinity for the hapten p-azophenylarsonate (Ars) into the preimmune antibody repertoire. The affinity of this V region for Ars is 100-fold higher than any unmutated anti-Ars antibody previously characterized. Expression of the transgene-encoded V region did not affect many aspects of antigen-driven B cell differentiation, including somatic hypermutation, in either Ars-specific transgene- or endogenous V gene-expressing clones. Thus, the regulation of these processes appears to operate in a "global" fashion, in that the mechanisms involved are imperceptive of the relative affinities for antigen of the antibodies expressed by B cell clones participating in the immune response. In contrast, the selection of V region mutants leading to affinity maturation and memory cell formation was found to be strongly influenced by the transgenic V region, but only in clones expressing this V region. Hybridomas derived from transgene- and endogenous V region-expressing memory cells were isolated at similar frequencies from individual transgenic mice. The V regions expressed by hybridomas in both of these groups had 2- to 30-fold greater affinity for Ars than their unmutated precursors, despite the fact that the transgene-encoded precursors had 100-fold higher affinity than their endogenous counterparts. These results show that the criterion for entry into the memory compartment is established not by the affinity of a B cell's V region relative to all other V regions expressed during the response, but by the affinity of this V region relative to its unmutated precursor. Thus, the development of B cell memory is regulated in a "clone-autonomous" fashion.

Hypermutation is observed only in antibody H chain V region transgenes that have recombined with endogenous immunoglobulin H DNA: implications for the location of cis-acting elements required for somatic mutation.

Mice with transgenes containing an antibody H chain V region (VHDJH) gene were used in an analysis of the cis-acting elements required for hypermutation of immunoglobulin (Ig) V genes. These transgenes can somatically recombine with endogenous IgH DNA, leading to the formation of functional heavy (H) chains partially encoded by the transgenic VHDJH. The transgenomes in the five different lines of mice analyzed contain as little as 150 bp, and as much as 2.8 kb of natural DNA flanking the 5' side of the VH and either 1.5 or 2.3 kb (including the intronic enhancer and 5' matrix attachment region [MAR]) flanking the 3' side of VH. Hybridomas were constructed from immunized transgenic mice, and transgenes present in these hybridomas that had or had not recombined to form functional H chain loci were sequenced. The data obtained show that: (a) the recombined transgenes contain hypermutated VH genes; and (b) among such transgenes, even those containing only 150 bp of natural VH 5' flanking sequence and several kilobases of 5' plasmid vector sequence display a frequency, distribution, and type of mutation characteristic of conventional IgH loci. The data also indicate that transgenic VHDJH genes that have not recombined with endogenous IgH DNA are not substrates for hypermutation, even if they are flanked by 2.8 kb of natural 5' DNA, and 2.3 kb of natural 3' DNA, including the JH2-JH4 region, a MAR, and the intronic enhancer. Collectively, the data suggest that sequences 5' of the VH promoter are dispensable, a VH promoter and the intronic IgH enhancer region are not sufficient, and a region(s) within or 3' of the IgH constant region locus is requisite, for hypermutation of Ig VH transgenes.

Different epitope structures select distinct mutant forms of an antibody variable region for expression during the immune response.

Antibody variable (V) regions that initially differ from one another by only single amino acid residues at VH-D and D-JH segment junctions (termed canonical V regions) can be elicited in strain A/J mice by three different haptens. Among such V regions an amino acid substitution due to somatic mutation is recurrently observed at VH CDR2 position 58, regardless of which of these haptens is used for immunization. This substitution confers upon a canonical V region a generic increase in affinity for all the haptens. Conversely, the type of amino acid substitution at VH position 59 resulting from somatic mutation that is recurrently observed among such V regions changes with the eliciting hapten, in a manner that correlates directly with the cognate affinity increases (or decreases) for hapten conferred by the observed substitutions. This small subregion of VH CDR2 therefore plays a major role in determining both affinity and specificity for antigen. The data confirm that affinity for antigen is of pivotal importance in determining the degree of selection of different mutant forms of a V region. Moreover, during an immune response a sufficiently diverse mutant repertoire can be generated from a single canonical V region to allow adaptation to increase affinity for three different epitopes.

Molecular analysis of original antigenic sin. I. Clonal selection, somatic mutation, and isotype switching during a memory B cell response.

To determine how the memory B cell population elicited to one epitope might be used in immune responses to other, structurally related epitopes, we explored the phenomenon of original antigenic sin. Strain A/J mice reproducibly respond to immunization with p-azophenylarsonate (Ars) by production of anti-Ars antibodies encoded predominantly by a single VH gene segment (VHIdCR). The structural analogue of Ars p-azophenylsulfonate (Sulf) fails alone to elicit such V regions, but can do so in A/J mice previously immunized with Ars, providing a means to specifically examine B cells capable of responding secondarily to a crossreactive antigen (i.e., memory cells). VHIdCR-expressing hybridomas were derived from the Ars-primed, Sulf-boosted original antigenic sin response of A/J mice at various times after Ars priming, and the properties of the antibodies they express and the structure of the genes encoding these antibodies were characterized. The data obtained support the following conclusions: (a) The Ars-induced memory B cell population capable of being crossreactively stimulated by Sulf is largely formed from a small fraction of all B cells participating in the anti-Ars primary response that express somatically mutated V regions; (b) the antibody repertoire and clonal composition of this population are stable over long periods of time; (c) memory B cells are capable of clonal expansion in the absence of a high rate of V gene somatic mutation; (d) the activation requirements for clonal selection of memory, versus naive B cells appear to differ; and (e) a major fraction of Ars-induced memory B cells express either IgM or IgG3 prior to and during the initial stages of the sin response.

Somatically mutated forms of a major anti-p-azophenylarsonate antibody variable region with drastically reduced affinity for p-azophenylarsonate. By-products of an antigen-driven immune response?

The pivotal role played by antigen in the clonal selection of B cells for initial participation in an immune response is well established. Antigen selective mechanisms ensure that antigen-binding antibodies are produced during all stages of the immune response. However, antibodies that lack specificity for the immunogen might also be produced during the course of an antigen-driven immune response . It has been suggested that, through idiotype-antiidiotype network interactions within the immune system, production of antibodies that lack specificity for the immunogen but that share idiotopes with antigen-binding antibodies could result (1). In addition, data obtained by a number of investigators suggest that somatic mutation of antibody V region genes occurs at a rate of 10(-3)/basepair/cell division in B cells participating in an immune response (2, 3). One outcome of such V region structural alteration could be antibodies that lack, or have drastically reduced affinity for the immunogen . We sought to identify and characterize some of the antibody by-products of the antigen-driven immune response that are expected to be created by the mechanisms described above.

Regulation of the immune response to peptide antigens: differential induction of immediate-type hypersensitivity and T cell proliferation due to changes in either peptide structure or major histocompatibility complex haplotype.

The immunodominant CD4 T cell epitope of the bacteriophage lambda cI repressor protein in several inbred mouse strains can be represented by a peptide encompassing amino acids 12-26. Here, we show that this peptide, and a variety of its sequence variants, can induce immediate-type hypersensitivity in mice. 12-26 variants that differ by as little as single amino acid residues deviate greatly in their ability to induce hypersensitivity. Further, differences in major histocompatibility complex class II alleles appear to be as influential as changes in peptide structure in determining whether hypersensitivity is developed. The ability of a given peptide-class II combination to induce hypersensitivity correlates with production of peptide-specific antibody, but not with ability or inability to induce a T cell proliferative response. Administration of anti-interleukin 4 (IL-4) mAb prevents the development of hypersensitivity, and analysis of cytokine production by T cell hybridomas derived from peptide-immunized mice suggests that whether a given peptide-class II combination can induce hypersensitivity depends on its ability to induce IL-4 production. The data demonstrate that changes in the nature of the epitope(s) recognized by the CD4 T cell population can result in qualitative differences in the response elicited in this population, ultimately leading to dramatic quantitative and qualitative variations in the effector phase of the immune response.

A single germline VH gene segment of normal A/J mice encodes autoantibodies characteristic of systemic lupus erythematosus.

These experiments tested the hypothesis that unmutated germline genes from normal mice can encode autoantibodies. We found that the unmutated VHIdCR gene segment, which encodes a large proportion of antiarsonate antibodies in A/J mice, also encodes antibodies with the ability to bind to DNA and cytoskeletal proteins. After Ars immunization, at a time when the VHIdCR gene segment mutates and antibody affinity for the hapten increases, reactivity with the autoantigens was lost. Six antibodies obtained after immunization with Ars bound both the Ars and DNA. Results of competitive inhibition assays suggested that the same variable region site in the antibodies bound to both Ars and DNA. The properties of the individual germline-encoded antibodies, which include reactivity to both DNA and cytoskeletal proteins, suggest that autoantibodies characteristic of SLE might be a subset of antibodies encoded by unmutated germline V genes.

Severe attenuation of the B cell immune response in Msh2-deficient mice.

Recently, results obtained from mice with targeted inactivations of postreplication DNA mismatch repair (MMR) genes have been interpreted to demonstrate a direct role for MMR in antibody variable (V) gene hypermutation. Here we show that mice that do not express the MMR factor Msh2 have wide-ranging defects in antigen-driven B cell responses. These include lack of progression of the germinal center (GC) reaction associated with increased intra-GC apoptosis, severely diminished antigen-specific immunoglobulin G responses, and near absence of anamnestic responses. Mice heterozygous for the Msh2 deficiency display an "intermediate" phenotype in these regards, suggesting that normal levels of Msh2 expression are critical for the B cell response. Interpretation of the impact of an MMR deficiency on the mechanism of V gene somatic hypermutation could be easily confounded by these perturbations.

A novel mechanism for B cell repertoire maturation based on response by B cell precursors to pre-B receptor assembly.

The expression of different sets of immunoglobulin specificities by fetal and adult B lymphocytes is a long-standing puzzle in immunology. Recently it has become clear that production of immunoglobulin mu heavy chain and subsequent assembly with a surrogate light chain to form the pre-B cell receptor complex is critical for development of B cells. Here we show that instead of promoting pre-B cell progression as in adult bone marrow, this complex inhibits pre-B cell growth in fetal liver. Curiously, we identify a fetal-associated VH11 mu heavy chain that allows continued pre-B proliferation in fetal liver. Interestingly, this heavy chain does not associate efficiently with a surrogate light chain, providing a previously unrecognized mechanism for skewing the expression of distinctive VH genes toward fetal through early neonatal life.