Consistent Minimization of Clustering Objective Functions

International audienceClustering is often formulated as a discrete optimization problem. The objective is to find, among all partitions of the data set, the best one according to some quality measure. However, in the statistical setting where we assume that the finite data set has been sampled from some underlying space, the goal is not to find the best partition of the given sample, but to approximate the true partition of the underlying space. We argue that the discrete optimization approach usually does not achieve this goal. As an alternative, we suggest the paradigm of ``nearest neighbor clustering''. Instead of selecting the best out of all partitions of the sample, it only considers partitions in some restricted function class. Using tools from statistical learning theory we prove that nearest neighbor clustering is statistically consistent. Moreover, its worst case complexity is polynomial by construction, and it can be implemented with small average case complexity using branch and bound

requirements for naive CD4+ T cell stimulation

Human primary dendritic cells (DCs) are heterogeneous by phenotype, function, and tissue localization and distinct from inflammatory monocyte-derived DCs. Current information regarding the susceptibility and functional role of primary human DC subsets to Mycobacterium tuberculosis (Mtb) infection is limited. Here, we dissect the response of different primary DC subsets to Mtb infection. Myeloid CD11c+ cells and pDCs (C-type lectin 4C+ cells) were located in human lymph nodes (LNs) of tuberculosis (TB) patients by histochemistry. Rare CD141hi DCs (C-type lectin 9A+ cells) were also identified. Infection with live Mtb revealed a higher responsiveness of myeloid CD1c+ DCs compared to CD141hi DCs and pDCs. CD1c+ DCs produced interleukin (IL)-6, tumor necrosis factor α, and IL-1β but not IL-12p70, a cytokine important for Th1 activation and host defenses against Mtb. Yet, CD1c+ DCs were able to activate autologous naïve CD4+ T cells. By combining cell purification with fluorescence-activated cell sorting and gene expression profiling on rare cell populations, we detected in responding CD4+ T cells, genes related to effector-cytolytic functions and transcription factors associated with Th1, Th17, and Treg polarization, suggesting multifunctional properties in our experimental conditions. Finally, immunohistologic analyses revealed contact between CD11c+ cells and pDCs in LNs of TB patients and in vitro data suggest that cooperation between Mtb-infected CD1c+ DCs and pDCs favors stimulation of CD4+ T cells

The Proteasome System in Infection: Impact of β5 and LMP7 on Composition, Maturation and Quantity of Active Proteasome Complexes

Proteasomes are the major enzyme complexes for non-lysosomal protein degradation in eukaryotic cells. Mammals express two sets of catalytic subunits: the constitutive subunits β1, β2 and β5 and the immunosubunits LMP2 (β1i), MECL-1 (β2i) and LMP7 (β5i). The LMP7-propeptide (proLMP7) is required for optimal maturation of LMP2/MECL-1-containing precursors to mature immunoproteasomes, but can also mediate efficient integration into mixed proteasomes containing β1 and β2. In contrast, the β5-propeptide (proβ5) has been suggested to promote preferential integration into β1/β2-containing precursors, consequently favouring the formation of constitutive proteasomes. Here, we show that proβ5 predominantly promotes integration into LMP2/MECL-1-containing precursors in IFNγ-stimulated, LMP7-deficient cells and infected LMP7-deficient mice. This demonstrates that proβ5 does not direct preferential integration into β1/β2-containing precursors, but instead promotes the formation of mixed LMP2/MECL-1/β5 proteasomes under inflammatory conditions. Moreover, the propeptides substantially differ in their capacity to promote proteasome maturation, with proLMP7 showing a significantly higher chaperone activity as compared to proβ5. Increased efficiency of proteasome maturation mediated by proLMP7 is required for optimal MHC class I cell surface expression and is equally important as the catalytic activity of immunoproteasomes. Intriguingly, induction of LMP7 by infection not only results in rapid exchange of constitutive by immunosubunits, as previously suggested, but also increases the total proteasome abundance within the infected tissue. Hence our data identify a novel LMP7-dependend mechanism to enhance the activity of the proteasome system in infection, which is based on the high chaperone activity of proLMP7 and relies on accelerated maturation of active proteasome complexes

Communication between Human Dendritic Cell Subsets in Tuberculosis: Requirements for Naive CD4+ T Cell Stimulation

Human primary dendritic cells (DCs) are heterogeneous by phenotype, function and tissue localization and distinct from inflammatory monocyte-derived DCs. Current information regarding the susceptibility and functional role of primary human DC subsets to Mycobacterium tuberculosis (Mtb) infection is limited. Here, we dissect the response of different primary DC subsets to Mtb infection. Myeloid CD11c+ cells and pDCs (C-type lectin 4C+ cells) were located in human lymph nodes (LNs) of tuberculosis (TB) patients by histochemistry. Rare CD141hi DCs (C-type lectin 9A+ cells) were also identified. Infection with live Mtb revealed a higher responsiveness of myeloid CD1c+ DCs compared to CD141hi DCs and pDCs. CD1c+ DCs produced interleukin (IL)-6, tumor necrosis factor α and IL-1β but not IL-12p70, a cytokine important for Th1 activation and host defenses against Mtb. Yet, CD1c+ DCs were able to activate autologous naïve CD4+ T cells. By combining cell purification with fluorescence-activated cell sorting and gene expression profiling on rare cell populations, we detected in responding CD4+ T cells, genes related to effector-cytolytic functions and transcription factors associated with Th1, Th17 and Treg polarization, suggesting multifunctional properties in our experimental conditions. Finally, immunohistologic analyses revealed contact between CD11c+ cells and pDCs in LNs of TB patients and in vitro data suggest that cooperation between Mtb-infected CD1c+ DCs and pDCs favors stimulation of CD4+ T cells

Zurich Consensus: German Expert Opinion on the St. Gallen Votes on 15 March 2009 (11th International Conference at St. Gallen: Primary Therapy of Early Breast Cancer)

A German working group of 23 breast cancer experts discussed the results from the vote at this year's St. Gallen Consensus Conference on Primary Therapy for Early Breast Cancer ( March 11-14, 2009) and came up with some concrete recommendations for day-to-day therapeutic decisions in Germany. Due the fact that the concept of the St. Gallen Consensus Conference merely allows for a minimal consensus, the objective of the working group was to provide practice-related recommendations for day-to-day clinical decisions in Germany. One area of emphasis at St. Gallen was tumor biology as a starting point for reaching individual therapeutic decisions. Intensive discussion was necessary with respect to the clinical relevance of predictive and prognostic factors. A new addition to the area of systemic therapy was a first-ever discussion of the adjuvant administration of bisphosponates and the fact that therapy with trastuzumab in HER2 overexpressing breast cancer has been defined as the standard for neoadjuvant therapy. The value of taxanes as a component of (neo) adjuvant chemotherapy as well as the value of aromatase inhibitors for the endocrine adjuvant treatment of postmenopausal patients were affirmed

Link between Organ-specific Antigen Processing by 20S Proteasomes and CD8+ T Cell–mediated Autoimmunity

Adoptive transfer of cross-reactive HSP60-specific CD8+ T cells into immunodeficient mice causes autoimmune intestinal pathology restricted to the small intestine. We wondered whether local immunopathology induced by CD8+ T cells can be explained by tissue-specific differences in proteasome-mediated processing of major histocompatibility complex class I T cell epitopes. Our experiments demonstrate that 20S proteasomes of different organs display a characteristic composition of α and β chain subunits and produce distinct peptide fragments with respect to both quality and quantity. Digests of HSP60 polypeptides by 20S proteasomes show most efficient generation of the pathology related CD8+ T cell epitope in the small intestine. Further, we demonstrate that the organ-specific potential to produce defined T cell epitopes reflects quantities that are relevant for cytotoxic T lymphocyte recognition. We propose tissue-specific antigen processing by 20S proteasomes as a potential mechanism to control organ-specific immune responses

Treatment trajectories of gender incongruent Austrian youth seeking gender-affirming hormone therapy

ObjectiveThe aim of this study was to describe the treatment trajectories of Austrian children and adolescents with gender incongruence seeking gender-affirming medical care.MethodsPatients who presented with gender incongruence at the pediatric outpatient clinic for differences in sex development at a large university hospital in Austria from January 2008 to December 2022 were included in a retrospective chart review, and analyzed regarding referral numbers, patient characteristics, treatment trajectories, fertility preservation, and legal gender marker changes.ResultsOf 310 eligible patients, 230 (74.2%) were assigned female at birth (AFAB), and 80 (25.8%) were assigned male at birth (AMAB). The number of referrals increased steeply from 2008 to 2018, whereafter it stabilized at around 50 per year. At the time of initial presentation, the median age of patients was 15.6 years (IQR 14.3-16.8). AMAB individuals tended to be younger (median 14.9 years, IQR 13.9-16.8) than AFAB individuals (median 15.8 years, IQR 14.4-16.8; p= 0.012). 207 (66,8%) completed the assessment process and were eligible for gender affirming medical treatment (GAMT). Of those, 89% (186/207) commenced gender affirming hormone therapy in the pediatric outpatient clinic (79/186 received GnRHa monotherapy, 91/186 GnRHa and sex steroids, and 16/186 sex steroid monotherapy). Of the 54 AMAB individuals receiving GAMT, 6 (11.1%) completed fertility preservation prior to therapy initiation. Only 1/132 AFAB adolescents receiving GAMT completed fertility preservation. Chest masculinization surgery was performed in 22 cases (16.7%), and breast augmentation in two cases (3.7%) between the ages of 16 and 18. Changes in legal gender marker were common, with 205 individuals (66.1%) having changed their legal gender marker.ConclusionThis is the first time that treatment trajectories, fertility preservation rates, and changes of legal gender marker have been described in Austrian adolescents with gender incongruence seeking GAMT. The majority received GAMT and changed their legal gender marker, while gender affirming surgery rates were low, and utilization of fertility preservation treatment options was rare

Zurich Consensus: Statement of German Experts on St. Gallen Conference 2011 on Primary Breast Cancer (Zurich 2011)

Every 2 years, the International Consensus Conference on the Treatment of Primary Breast Cancer takes place in St. Gallen. Given that the concept of the St. Gallen Consensus Conference mainly reflects an international opinion, it appears useful to adapt the results of the vote for everyday therapy in Germany. A German working group comprising 28 breast cancer experts, amongst whom there are 3 members of the international St. Gallen panel, has therefore commented on this year's St. Gallen Consensus Conference (2011) from the German viewpoint. The focus of interest of this year's St. Gallen Conference was tumour biology as the starting point for decisions regarding individual therapy. There was an intensive discussion in relation to the clinical relevance of predictive and prognostic factors and possible consequences for decisions regarding therapy. Therefore, questions concerning the indication for adjuvant chemotherapy focused especially on the significance of the molecular phenotype of the tumour. In addition, important points for discussion were also the value of complete axillary dissection and the use of accelerated complete breast irradiation