A concept for integrated care pathways for atopic dermatitis-A GA2 LEN ADCARE initiative

INTRODUCTION

The integrated care pathways for atopic dermatitis (AD-ICPs) aim to bridge the gap between existing AD treatment evidence-based guidelines and expert opinion based on daily practice by offering a structured multidisciplinary plan for patient management of AD. ICPs have the potential to enhance guideline recommendations by combining interventions and aspects from different guidelines, integrating quality assurance, and describing co-ordination of care. Most importantly, patients can enter the ICPs at any level depending on AD severity, resources available in their country, and economic factors such as differences in insurance reimbursement systems.

METHODS

The GA2 LEN ADCARE network and partners as well as all stakeholders, abbreviated as the AD-ICPs working group, were involved in the discussion and preparation of the AD ICPs during a series of subgroup workshops and meetings in years 2020 and 2021, after which the document was circulated within all GAL2 EN ADCARE centres.

RESULTS

The AD-ICPs outline the diagnostic procedures, possible co-morbidities, different available treatment options including differential approaches for the pediatric population, and the role of the pharmacists and other stakeholders, as well as remaining unmet needs in the management of AD.

CONCLUSION

The AD-ICPs provide a multidisciplinary plan for improved diagnosis, treatment, and patient feedback in AD management, as well as addressing critical unmet needs, including improved access to care, training specialists, implementation of educational programs, assessment on the impact of climate change, and fostering a personalised treatment approach. By focusing on these key areas, the initiative aims to pave the way for a brighter future in the management of AD.

Physiopathologie de la dermatite atopique et des autres maladies atopiques : une approche globale est-elle possible ?

Atopy is defined by the propensity to develop an exaggerated type-2 inflammatory response to environmental molecules. Clinically, atopy is diagnosed when atopic disease occurs: atopic dermatitis, food allergy, atopic asthma and allergic rhinitis and conjunctivitis. Whereas the classical "atopic march" is increasingly challenged through epidemiological studies, type-2 cellular inflammation is a characteristic shared by the atopic diseases. This inflammation can be innate (non-specific: eosinophils, mast cells, dendritic cells, innate lymphoid cells [ILC]), or adaptive (antigen-specific, involving T cells). Interleukins (IL-)4, 5 and 13 are major actors of type-2 inflammation and are mainly produced by ILC and T cells. The efficacy of treatments targeting these type-2 cytokines highlight the importance of type-2 inflammation in atopic diseases. However, several patients do not respond to type-2 targeting treatments, highlighting the presence of other actors in pathophysiology of atopic diseases: alteration of epithelial barrier, IgE-mediated allergic responses, type-17 inflammation. Thus, the term "endotype" can illustrate this diversity in pathophysiology. Finally, a global approach of atopic diseases, as type-2 inflammatory diseases, is fundamental, but not sufficient. An approach by endotype is advisable, in a personalized medicine perspective. © 2020 Elsevier Masson SAS. All rights reserved.

Automatic depletion with Spectra Optia allows a safe 16% reduction of red blood cell pack consumption in exchanged sickle cell anemia patients

BACKGROUND

Chronic red blood cell exchanges (RBCXs) are frequently used to prevent complications in patients with sickle cell anemia, but the scarcity of matched red blood cell packs (RBCPs) is a serious concern. The main goal of this study was to compare the number of RBCPs used during RBCXs between the Spectra Optia (SO) device (with the automatic depletion step) and the former Cobe Spectra (CSP) device.

STUDY DESIGN AND METHODS

The performances and safety of 300 SO sessions using the automatic depletion step (SO/DE) in 50 patients with sickle cell anemia under a chronic transfusion program over a 1-year period were prospectively analyzed. The numbers of RBCPs saved using this protocol compared to the SO device without depletion and to the CSP device were determined.

RESULTS

The SO/DE protocol appeared to be safe, as only 5% and 17% of the sessions were characterized by a significant decrease in blood pressure and increase in heart rate (grade 2 adverse events), respectively. Postapheresis hematocrit and fraction of cells remaining reached expected values. The SO/DE protocol required 16% fewer RBCPs compared to SO without depletion, allowing a mean saving of 12 RBCPs per patient and per year and 13% fewer compared to CSP device. Interestingly, the saving was more important for patients with high total blood volume and/or high preapheresis hematocrit.

CONCLUSION

The SO/DE protocol is an efficient, safe and cost-effective procedure for patients with sickle cell anemia under a chronic transfusion program.

Corticosteroid cross-reactivity: clinical and molecular modelling tools

BACKGROUND

Corticosteroids have been classified into following four cross-reacting groups in function of their contact-allergenic properties: A, B, C and D, the last subdivided into D1 and D2. Recent data indicate that C(16)-methylated and nonmethylated molecules need to be distinguished, the latter selectively binding with arginine to form stable cyclic adducts and producing considerably more positive reactions than the former. This study compares molecular modelling and patch-test results to determine cross-reactivity patterns.

METHODS

The patch-test results obtained with 66 corticosteroid molecules in 315 previously sensitized subjects were analysed and correlated with modelling and clustering in function of the electrostatic and steric fields of these molecules.

RESULTS

The classification obtained after in silico hydrolysis of C(21) and C(17) esters was selected with an optimal cut into three clusters: the patients who reacted positively to cluster 2 (halogenated molecules from group B, with C(16)/C(17) cis ketal or diol structure) and cluster 3 (halogenated molecules from groups C and D1, C(16)-methylated) also reacted to cluster 1 (molecules mostly from groups A and D2, without C(16)-methyl substitution or halogenation and budesonide). The reverse, however, was not the case.

CONCLUSION

Two patient profiles with probably different areas of immune recognition are identified as follows: the profile 1 patients were allergic to the frequently positively reacting cluster 1 only, for whom electrostatic fields (molecular charge) seem important; the profile 2 patients reacted to clusters 1 and 2 and/or 3, for whom steric fields (structure) are determinant and who probably presented a global recognition of the corticosteroid skeleton. A modified classification is thus proposed.

The skin allergenic properties of chemicals may depend on contaminants--evidence from studies on coumarin

BACKGROUND/AIMS

Positive patch tests are considered representative of a contact allergy to the tested chemical. However, contaminants and derivatives rather than the suspected chemical itself could be responsible for the allergic skin reactions. Here, we tested the importance of contaminants in the sensitizing and allergenic properties of coumarin in mice and humans. Coumarin, an ingredient in cosmetics and fragrances, was chosen as the reference chemical since conflicting results have been obtained regarding its ability to induce contact allergy. In some chemical preparations, this could be explained by the presence of coumarin derivatives endowed with allergenic properties.

METHODS

In mice, three different coumarin preparations were tested in the local lymph node assay. In humans, we assessed the irritant and allergenic properties of highly pure coumarin in nonallergic and fragrance-allergic patients.

RESULTS

Pure coumarin did not exhibit irritant or sensitizing properties in the local lymph node assay. In contrast, two other commercially available coumarins and three contaminants that were detected in these coumarin preparations were identified as weak and moderate sensitizers, respectively. In humans, pure coumarin was extremely well tolerated since only 1 out of 512 patients exhibited a positive patch test to the chemical.

CONCLUSIONS

These results indicate that coumarin cannot be considered as a common contact allergen and further emphasize that purity of chemicals is mandatory for the assessment of their allergenicity.

[Pathogenesis of atopic dermatitis]

Atopic dermatitis (AD) is a chronic inflammatory dermatosis due to the activation ofT-cell lymphocytes specific to protein antigens in the skin. The AD antigens come from molecules in the environment (extrinsic AD allergens associated with hyper IgE levels) or from self antigens (intrinsic AD autoantigens). The physiopathology of AD implies dendritic cells, specific T-cell lymphocytes, a network of type 1 and 2 cytokines and inflammatory chemokines. Extrinsic AD is the best known because of the existence of animal models and skin tests with allergens in humans (atopy patch tests), which reproduce eczema lesions. Although the role of the penetration of pneumo-allergens, prompted by abnormalities in the skin barrier, in inducing AD flares is established, recent works suggest that other types of allergens (trophallergens) and/or proteins derived from micro-organisms may be responsible in some patients. The ongoing studies on animal models of AD will no doubt permit rapid progression in our knowledge of the mechanisms involved in the origin of the disease and the reasons for its progressive increase in frequency.

Photoageing shows histological features of chronic skin inflammation without clinical and molecular abnormalities

BACKGROUND

Photodamage is characterized by degradation of collagen and accumulation of abnormal elastin in the superficial dermis. Mast cells and macrophages, which are found in higher numbers in photoaged skin, have been implicated in this process.

OBJECTIVES

To analyse the phenotype of haematopoietic-derived infiltrating cells in photodamaged skin.

METHODS

Chronically sun-exposed (preauricular) and control sun-protected (postauricular) skin was recovered from eight healthy subjects undergoing cosmetic surgery (facial lifting).

RESULTS

Histological analysis showed that sun-exposed skin harboured more infiltrating mononuclear cells than sun-protected skin. Cellular infiltrates were found at the periphery of areas of elastolysis around hair follicles in sun-exposed sites, whereas they were found in the interfollicular dermis around blood vessels and around hair follicles in sun-protected samples. Immunohistochemical analysis revealed an increased number of mast cells, macrophages and CD4+ CD45RO+ T cells in sun-exposed dermis as well as a higher number of CD1a+ dendritic cells in sun-exposed epidermis, compared with the sun-protected samples. Thus photoageing displays histological features of chronic skin inflammation. However, no molecular sign of inflammation was observed and we even found a decreased expression of interleukin-1beta mRNA in sun-exposed compared with sun-protected sites. Furthermore, the patients' skin looked normal and did not display any clinical inflammation.

CONCLUSIONS

Collectively, these data show that chronic ultraviolet irradiation induces alterations of innate immune cells which are recruited in sun-exposed skin without being activated.

Decreased expression of keratinocyte beta1 integrins in chronically sun-exposed skin in vivo

BACKGROUND

Chronic exposure to ultraviolet (UV) radiation induces changes in the skin structure which are mostly found in the superficial dermis and at the dermal-epidermal junction. Keratinocytes and fibroblasts contribute both to the synthesis and to the degradation of the molecules important for the integrity of this skin site. While several studies have reported on alterations of dermal components and of the functions of fibroblasts in vivo and in vitro after UV exposure, recent data suggested that keratinocytes could be the main skin cell type involved in the photoageing process.

OBJECTIVES

In this study, we analysed the expression of two keratinocyte molecules namely, beta1 integrin (a proliferation marker) and involucrin (a differentiation marker) in sun-exposed and sun-protected facial skin of 16 healthy patients undergoing facial lifting.

METHODS

Methods included histology, immunohistochemistry and quantitative reverse transcriptase-polymerase chain reaction analysis.

RESULTS

Sun-exposed skin displayed the characteristic morphological and molecular features of dermal photoageing, compared with sun-protected skin, including dermal elastosis, diminished fibrillin and type VII collagen expression. Analysis of the epidermis in sun-exposed vs. sun-protected skin showed no histological differences, but dramatic changes in the expression of beta1 integrin and involucrin. In sun-exposed skin, expression of beta1 integrin protein by epidermal basal cells was reduced, paralleling a downregulation of beta1 integrin mRNA, whereas involucrin protein expression was greatly enhanced in the superficial epidermal cell layers. Interestingly, the ratio between involucrin and beta1 integrin protein expression was consistently increased in sun-exposed skin sites.

CONCLUSIONS

Collectively these results demonstrate that epidermal homeostasis is impaired by chronic UV exposure, and define beta1 integrin expression as a molecular marker of the epidermal photoageing process.

Afferent and efferent phases of allergic contact dermatitis (ACD) can be induced after a single skin contact with haptens: evidence using a mouse model of primary ACD

Allergic contact dermatitis is a T cell-mediated delayed type hypersensitivity reaction that occurs upon hapten challenge in sensitized individuals. The inflammatory response in classical allergic contact dermatitis requires both a sensitization phase and an elicitation phase responsible for the recruitment and activation of specific T cells at the site of hapten skin challenge. Conversely, previously unsensitized patients may develop a "primary allergic contact dermatitis" after the first skin contact with potent contact sensitizers leading to a skin inflammation with all the features of classical allergic contact dermatitis. In this study we used an experimental murine model, referred to as contact hypersensitivity, to study the pathophysiology of primary allergic contact dermatitis and its relationship to classical allergic contact dermatitis. We show that one epicutaneous application of a nonirritant dose of hapten (2,4-dini-trofluorobenzene, fluorescein isothiocyanate) was sufficient to induce an optimal allergic contact dermatitis reaction at the site of primary contact with the hapten without subsequent challenge. As in classical allergic contact dermatitis, the skin inflammation in primary allergic contact dermatitis was mediated by interferon-gamma producing, CD8+ effector T cells that were induced in the draining lymph nodes at day 5 postsensitization and downregulated by CD4+ T cells. Reverse transcription-polymerase chain reaction analysis revealed that the primary allergic contact dermatitis reaction was mediated by a recruitment of CD8+ T cells at the sensitization skin site at day 6 postsensitization. Analysis of the fate of the hapten fluorescein isothiocyanate applied once on the skin revealed its persistence in the epidermis for up to 14 d after skin painting. These results suggest that the development of primary allergic contact dermatitis (i.e., without secondary challenge) is associated with persistence of the hapten in the skin, which allows the recruitment and activation of CD8+ T cells at the site of the single hapten application.

Intra-individual comparison of the cutaneous safety and efficacy of calcitriol 3 microg g(-1) ointment and calcipotriol 50 microg g(-1) ointment on chronic plaque psoriasis localized in facial, hairline, retroauricular or flexural areas

BACKGROUND

Psoriasis involving sensitive skin areas remains difficult to treat because of the side-effects of topical corticosteroids and the irritancy potential of vitamin D3 derivatives. Several clinical trials have demonstrated that calcitriol, the naturally occurring and hormonally active form of vitamin D3, is effective and safe at the dose of 3 microg g(-1) for the treatment of psoriasis affecting the trunk and limbs.

METHODS

We compared the safety and efficacy of calcitriol 3 microg g(-1) ointment and calcipotriol 50 microg g(-1) ointment in a multicentre, randomized, investigator-blinded, left-right comparison in mild to moderate chronic plaque psoriasis affecting sensitive areas, defined as being the face, hairline, retroauricular and flexural areas. One pair of symmetrical and bilateral target lesions was selected from each area and assessed for perilesional erythema, oedema, and stinging/burning. Global assessment of local tolerability and global improvement were rated by the investigator, and the subjects were asked to evaluate the tolerability and efficacy of each product and to express their global preference.

RESULTS

In the 75 subjects, calcitriol and calcipotriol both led to clearing of at least one target lesion in 21 (28%) of the subjects each. Perilesional erythema (P < 0.001), perilesional oedema (P < 0.02) and stinging/burning (P < 0.001) were all significantly less severe with calcitriol than with calcipotriol. The subjects' evaluation of local tolerability was significantly (P < 0.0001) in favour of calcitriol. Ten treatment-related dermatological events occurred in eight subjects, including one subject who experienced skin discomfort on both sides. All other events occurred only on the calcipotriol-treated side (irritant dermatitis, six subjects; contact dermatitis, one subject). Global assessment of improvement from baseline by the investigators was significantly greater for the calcitriol-treated lesions (P < 0.02). The subjects' global preference was significantly in favour of calcitriol (P < 0.02).

CONCLUSIONS

In the present study, calcitriol ointment was found to be better tolerated and would appear to be more effective than calcipotriol ointment in the treatment of psoriasis in sensitive areas.

Signaling from epithelial to dendritic cells of the thyroid gland: evidence for thyrocyte-derived factors controlling the survival, multiplication, and endocytic activity of dendritic cells

Intrathyroidal dendritic cells (DC) isolated at the same time and then cultured with thyrocytes in the presence of thyrotropin (TSH) keep a phenotype of immature DC (Croizet et al, 2000). As DC from other sources are known to undergo a rapid maturation in vitro, we hypothesized that the maintenance of thyroid-derived DC in an immature state might be caused by thyrocytes-DC interactions. In this study, we investigated whether thyroid-derived DC could change their phenotype in response to TSH stimulation of thyrocytes. Over an 8-day period of culture, the population of DC increased 2- to 3-fold in the presence of TSH and decreased by more than 75% in the absence of TSH. The increase in the DC population was related to DC proliferation, whereas the reduction of the number of DC was secondary to a loss of cell-substrate adhesion and subsequent cell death. In the presence of TSH, DC acquired and maintained a high capacity for internalizing labeled ligands, expressed the mannose receptor, and exposed MHC class II molecules at the cell surface. On the contrary, DC cultured without TSH were devoid of endocytic activity and mannose receptor and, after 2 days, no longer exposed MHC class II molecules at the cell surface. Using conditioned media and enriched DC populations, we show that thyrocytes, in response to TSH, produce soluble factors capable of activating proliferation and endocytic activity of DC. Exogenous granulocyte/macrophage-colony stimulating factor and transforming growth factor-beta, known to be produced by thyrocytes, reproduced the effects of conditioned media. These data, giving evidence of a hormone-regulated signaling process between epithelial and dendritic cells in vitro, suggest that thyrocytes could promote the maintenance of a population of immature DC within the thyroid gland.

Drug-induced urticaria

The occurrence of acute urticaria during treatment with drugs is a frequent event which poses two problems: 1) is the urticaria connected with the drug administration or with the underlying pathology which led to the prescription of the drug; 2) is the urticaria allergic in origin, i.e. due to specific immunity triggers, in particular IgE directed against the drug, or is the urticaria pseudo-allergic in origin, i.e. due to non-specific activation of mastocytes [1]? This question is of major importance because allergic events caused by IgE are potentially fatal while pseudo-allergic events are only rarely life-threatening. In this article we will not deal with contact urticaria where the cause is easily identifiable [2].

Mechanism of measles virus-induced suppression of inflammatory immune responses

Measles virus (MV) causes profound immunosuppression, resulting in high infant mortality. The mechanisms are poorly understood, largely due to the lack of a suitable animal model. Here, we report that particular MV proteins, in the absence of MV replication, could generate a systemic immunosuppression in mice through two pathways: (1) via MV-nucleoprotein and its receptor FcgammaR on dendritic cells; and (2) via virus envelope glycoproteins and the MV-hemagglutinin cellular receptor, CD46. The effects comprise reduced hypersensitivity responses associated with impaired function of dendritic cells, decreased production of IL-12, and the loss of antigen-specific T cell proliferation. These results introduce a novel model for testing the immunosuppressive potential of anti-measles vaccines and reveal a specific mechanism of MV-induced modulation of inflammatory reactions.

The human anti-bullous pemphigoid monoclonal autoantibody P22 is encoded by genes of the IGHV4 and IGLV4 families

We identified, cloned, and biochemically characterized the full-length cDNAs encoding the heavy and light chains of a human monoclonal antibody (mAb) from the Epstein-Barr virus (EBV)-cell line P22. The cell line P22, which originated from a patient with bullous pemphigoid (an autoimmune disease causing skin blistering) expressed immunoglobulin-G (IgG) with a lambda light chain. Although the variable heavy (IGHV) chain gene family could not be assigned by IGHV repertoire analysis, the determination of its nucleotide sequence demonstrated that the heavy chain of P22 belonged to the IGHV4 family. The limited IGHV4 gene usage by memory IgG, IGA and IgE-expressing cells supports the notion of the autoreactivity-associated IGHV4 genes and stresses the strong selection pressure within germinal centres towards IGHV4 family. Alignment of P22 IGHV4 cDNA sequence to germline sequences from gene databases, revealed a remarkable divergence, suggesting that the heavy chain of the P22 mAb encodes a distinct IGHV4 gene. The variable light chain (IGLV) encodes a IGLV4 gene and is 98% similar to a previously reported IGLV gene. Furthermore, fluorescent staining with the recombinant mAb showed the same reactivity to that of the native antibody. The data reported herein, (a) reveal an autoantibody encoding a distinct IGHV4 gene, (b) confirm the notion that autoantibodies preferentially use IGHV4 genes, and (c) hypothesize that somatic hypermutation within GC may be a mechanism by which autoreactive B lymphocytes escape negative selection.

Clonal organization in the postnatal mouse central nervous system is prefigured in the embryonic neuroepithelium

We have used the LaacZ clonal method of cell labeling of neuronal ancestors and report that the spatial organization of neuronal cells in the post-natal CNS shares striking similarities to that in the embryonic neuroepithelium, from the spinal cord to the diencephalon. The maintenance of the organization occurs despite massive cell divisions and morphogenetic movements. We deduce that the cellular and architectural organization in the mouse CNS results from a succession of patterns of oriented cell dispersion, a general arrest of cell dispersion in the neuroepithelium, and then well-documented radial neuronal migration. The arrest of cell dispersion in the neuroepithelium is consistent with the possibility that an important part of the cellular and architectural organization of the mature CNS requires conservation of spatial relationship between cells and supports the hypothesis of a transition from global and sparse to local and dense cell interactions occurring early within the neuroepithelium.

Culture of dendritic cells from a nonlymphoid organ, the thyroid gland: evidence for TNFalpha-dependent phenotypic changes of thyroid-derived dendritic cells

Because they are sparsely distributed in tissues, dendritic cells (DC) present in nonlymphoid organs are difficult to isolate. Only DC from skin and lung have been successfully studied in culture. The objective of the present work was to investigate the possibility of isolating and culturing DC from an endocrine organ, the thyroid gland, which is particularly susceptible to the development of autoimmune processes. The study was conducted on pig thyroid glands to have sufficient amounts of starting material. This choice required the characterization of immunological reagents capable of recognizing DC markers in the pig species. Using a discontinuous trypsinization procedure, a DC population representing 2% to 3% of the thyroid cell suspension was reproducibly obtained. Isolated DC quantitatively attached to tissue culture-treated dishes and segregated from thyrocytes. DC identified as cells expressing major histocompatibility complex class II molecules, the mannose receptor, and the S100 protein were found to have a high capacity to internalize labeled ligands, dextran, and mannosylated albumin. These cells had a phenotype of immature DC. Secondarily, a fraction of DC detached from culture dishes, and floating DC had low or no endocytic activity, a characteristic of mature DC. Treatment of DC/thyrocytes cocultures with tumor necrosis factor alpha (TNFalpha) activated the transformation of immature DC into mature DC. These data show that DC isolated from the thyroid gland can be maintained immature or activated to undergo maturation in primary culture. The procedure of cell isolation and culture should be adaptable to human thyroid tissue for in vitro analyses of DC-mediated immune responses.

The popliteal lymph node response to streptozotocin is under type 1, MHC class-I restricted, CD8(+) T-cell control

The popliteal lymph node (PLN) assay has been proposed to predict the 'autoimmunogenic' potential of xenobiotics. A better understanding of the processes involved in PLN responses is needed to establish the value of this assay for preclinical safety evaluation. In order to determine whether PLN responses involve CD4(+) or CD8(+) T-cells, the effects of streptozotocin (STZ), a prototypic immunotoxic compound, were analyzed after injection into the hind footpad of C57 BL/6 mice and major histocompatibility complex (MHC) class I or II deficient mice. The involvement of type 1 or type 2 cell control on the production of cytokine mRNAs was analyzed in lymph node cells by quantitative RT-PCR, together with the analysis of a wide range of cytokine mRNAs after STZ injection (IL-1alpha, IL-1beta, TNF-alpha, IFN-gamma, IL-2, IL-2 receptor, IL-4, IL-5, IL-6, IL-10 and IL-12). We have found that mice depleted in CD8(+) T-cells did not respond to STZ, whereas mice depleted in CD4(+) T-cells exhibited the expected positive PLN responses, with increased weight and cellularity indices. STZ induced a low production of interleukin (IL)-2 mRNAs, a mild increase in IL-1alpha and IL-6 mRNAs production, and a dramatic increase in IFN-gamma, IL-1beta, TNF-alpha, IL-12 and IL-2 receptor mRNAs, which correlated with positive PLN responses. No effects on IL-4, IL-5 and IL-10 mRNAs synthesis were noted. In CD8(+) T-cell deficient mice, there was no production of IFN-gamma or IL-6 mRNAs. These results suggest that PLN responses to STZ are under the control of type 1, MHC class-I-restricted, CD8(+) T-cells. This is in accordance to the known physiopathology of STZ-induced diabetes. Additional studies are necessary to establish the mechanism of CD8+ T-cell activation.

Sequential histological and immunohistochemical study of the skin of the first human hand allograft

BACKGROUND

On September 1998, the first human hand allograft was successfully performed in Lyon.

METHODS

A 48-year-old white man who had suffered accidental amputation of the arm in 1984, received a forearm and hand allograft from a 42-year-old white male cadaveric heart-beating donor. Immunosuppressive therapy included prednisone, mycophenolate mofetil, FK506, and antithymocyte globulins. Sequential skin biopsies were taken from the grafted limb and examined (immuno)histologically to detect a possible graft rejection and to evaluate the structural integrity of the skin of the allograft.

RESULTS

The skin showed histologically a normal appearance, except on days 57 and 63, when a mononuclear perivascular cell infiltrate was observed in the dermis; this appeared concomitantly with erythematous lesions of the skin that developed after a slight decrease of the immunosuppressive treatment. These changes were considered as signs of graft rejection, and were reversed by an increase of the immunosuppressive treatment. No skin necrosis was seen at any time. Immunohistochemically, the main cell types of the skin were present throughout the study. From day 77 onward the epidermis of the grafted hand harbored some epidermal Langerhans cells of recipient's origin.

CONCLUSION

This study shows that the skin of the hand allograft maintains overall a normal histological structure and contains most essential cell types, including cells of recipient origin, such as Langerhans cells. Furthermore, it shows that in this system of composite tissue transplantation, skin biopsies may reveal a starting graft rejection, before the appearance of clinically obvious lesions.

Different clonal dispersion in the rostral and caudal mouse central nervous system

We have performed a systematic clonal analysis to describe the modes of growth, dispersion and production of cells during the development of the mouse neural system. We have used mice expressing a LaacZ reporter gene under the control of the neuron specific enolase promoter to randomly generate LacZ clones in the central nervous system (CNS). We present evidence for (1) a pool of CNS founder cells that is not regionalized, i.e. give descendants dispersed along the entire A-P axis, (2) an early separation between pools of precursors for the anterior and posterior CNS and (3) distinct modes of production of progenitors in these two domains. More specifically, cell growth and dispersion of the progenitors follow a relatively coherent pattern throughout the anterior CNS, a mode that leads to a progressive regionalization of cell fates. In contrast, cell growth of progenitors of the SC appears to involve self-renewing stem cells that progress caudally during regression of the mode. Therefore, at least part of the area surrounding the node is composed of precursors with self-renewing properties and the development of the trunk is dependent on pools of stem cells regressing from A to P. Taken together with our analysis of the cell growth changes associated with neuromere formation (Mathis, L., Sieur, J., Voiculescu, O., Charnay, P. and Nicolas, J. F. (1999) Development 126, 4095–4106), our results suggest that major transitions in CNS development correspond to changes in cell behavior and may provide a link between morphogenesis and genetic patterning mechanisms (i.e. formation of the body plan).

Oral administration of hapten inhibits in vivo induction of specific cytotoxic CD8+ T cells mediating tissue inflammation: a role for regulatory CD4+ T cells

We investigated whether oral tolerance could block the development of an inflammatory response mediated by CD8+ T cells, using a mouse model of oral tolerance of contact sensitivity (CS) to the hapten 2, 4-dinitrofluorobenzene (DNFB). In this system, the skin inflammatory response is initiated by hapten-specific class I-restricted cytotoxic CD8+ T (CTL) cells, independently of CD4 help. Oral delivery of DNFB before skin sensitization blocked the CS response by impairing the development of DNFB-specific CD8+ effector T cells in secondary lymphoid organs. This was shown by complete inhibition of DNFB-specific CTL and proliferative responses of CD8+ T cells, lack of specific IFN-gamma-producing CD8+ T cells, and inability of CD8+ T cells to transfer CS in RAG20/0 mice. RT-PCR and immunohistochemical analysis confirmed that recruitment of CD8+ effectors of CS in the skin at the site of hapten challenge was impaired in orally tolerized mice. Sequential anti-CD4 Ab treatment showed that only depletion of CD4+ T cells during the afferent phase of CS abrogated oral tolerance induction by restoring high numbers of specific CD8+ effectors in lymphoid organs, whereas CD4 depletion during the efferent phase of CS did not affect oral tolerance. These data demonstrate that a single intragastric administration of hapten can block in vivo induction of DNFB-specific CD8+ CTL responsible for tissue inflammation and that a subset of regulatory CD4+ T cells mediate oral tolerance by inhibiting expansion of specific CD8+ effectors in lymph nodes.

[LagoZ and LagZ, 2 genes depleted of CpG dinucleotides, derived from the LacZ gene for the study of epigenetic control]

The methylation of 5'CpG 3' dinucleotides within genes creates potential targets for protein complexes that bind to methylated DNA sequences and to histone deacetylases (MBD-HDAC). This can lead to transcriptional repression by modification of chromatic. To test the importance of this repression in vivo and to determine when during development these epigenetic controls are placed on genes, two novel genes have been engineered by directed mutagenesis of the CpG-rich LacZ gene that are depleted of (LagZ) or completely lacking (LagoZ) CpG sequences. We report that the expression (transcriptional and translational) of the three genes is indistinguishable in transient assays in cleaving mouse embryos. Therefore, the complete absence of CpG sequences within three kilobases of coding sequence is compatible with its maintenance in the nucleus and with its expression. These molecules can now be used to study the ontogenesis of the CpG-dependent repressive system in intact organisms.

[Biological diagnosis of immediate drug allergy. Comparative study of histamine liberation tests and CD63 expression by flow cytometry (preliminary results)]

The diagnosis of drug allergy is mainly based upon a detailed clinical history, positive skin tests (ST) and detection of specific IgE. In case of discrepant results, in vitro investigations to identify the responsible drug are needed. The histamine release test (HR) is usually performed. Nevertheless, its clinical benefit remains controversial. Flow cytometric methods (FCM) for the study of allergen induced basophil activation have been recently described. We assessed their usefulness in the diagnosis of drug allergy in comparison to HR results. Eighteen patients were included and 24 drugs (mainly antibiotics and muscle relaxant drugs) were tested. On the basis of clinical signs, 15 patients were classified as allergic (18 drugs). Sensitivity of biological investigations were found as follows: 71% (ST), 71% (FCM) and 24% (HR). This suggests performing FCM rather than HR. In addition, HR is more costly in terms of both reagents and laboratory technician time. Thus, CD63 detection by FCM seems to be a more reliable method in the clinical immunology laboratory. Additional data are needed to validate these preliminary results (sensitivity and specificity, especially in atopic patients) and to assess the interest of the method to investigate drug allergy due to other types of molecules.

Successive patterns of clonal cell dispersion in relation to neuromeric subdivision in the mouse neuroepithelium

We made use of the laacz procedure of single-cell labelling to visualize clones labelled before neuromere formation, in 12.5-day mouse embryos. This allowed us to deduce two successive phases of cell dispersion in the formation of the rhombencephalon: an initial anterior-posterior (AP) cell dispersion, followed by an asymmetrical dorsoventral (DV) cell distribution during which AP cell dispersion occurs in territories smaller than one rhombomere. We conclude that the general arrest of AP cell dispersion precedes the onset of morphological segmentation and is not imposed by the interface between adjacent rhombomeres. This demonstrates a major change in the mode of epithelial growth that precedes or accompanies the formation of neuromeres. We also deduced that the period of DV cell dispersion in the neuroepithelium is followed by a coherent growth phase. These results suggest a cell organization on a Cartesian grid, the coordinates of which correspond to the AP and DV axis of the neural tube. A similar sequence of AP cell dispersion followed by an arrest of AP cell dispersion, a preferential DV cell dispersion and then by a coherent neuroepithelial growth, is also observed in the spinal cord and mesencephalon. This demonstrates that a similar cascade of cell events occurs in these different domains of the CNS. In the prosencephalon, differences in spatial constraints may explain the variability in the orientation of cell clusters. Genetic and clonal patterning in the AP and DV dimensions follow the same spatial sequence. An interesting possibility is that these successive patterns of cell growth facilitate the acquisition of positional information.

T-cell repertoire analysis in chronic plaque psoriasis suggests an antigen-specific immune response

Psoriasis is a chronic inflammatory cutaneous disease of unknown etiology. Activation of T cells is thought to play a major role in the pathophysiology of psoriasis. In order to gain insight into the nature of the antigen (superantigen or nominal protein antigen) involved in psoriatic lesions, we have used a RT-PCR method to analyze the frequency of the 24 T cell receptor V beta chain (TCRBV) subfamilies and the size of the antigen-binding region (CDR3), using the immunoscope assay, in skin lesions of patients with chronic plaque-type psoriasis. Semi-quantitative analysis showed that no significant difference in V beta subfamily usage could be detected in T lymphocytes infiltrating lesional skin as compared to blood lymphocytes. Alternatively, determination of the size distribution of the CDR3 of all the V beta subfamilies revealed only in psoriatic skin a marked TCR oligoclonality defined by the presence in 3 to 5 V beta subfamilies of a single predominant CDR3 size which was associated with a unique V beta-J beta combination. Identical patterns of CDR3 length and V beta-J beta combination profiles were found in symetrical lesional sites from two psoriatic patients. This type of skewed CDR3 size profile is reminiscent of a local stimulation of T lymphocytes by nominal protein antigens. These data suggest that T lymphocytes infiltrating plaque-type psoriatic skin comprise expansions of oligoclonal T cells in response to stimulation by an antigen present in the skin.

Contact dermatitis II. Clinical aspects and diagnosis

Contact dermatitis (CD) is an altered state of skin reactivity induced by exposure to an external agent. "Eczema" and "dermatitis" are often used synonymously to denote a polymorphic pattern of inflammation of the skin characterized, at least in its acute phase, by erythema, vesiculation and pruritus. Substances that induce CD after single or multiple exposures may be irritant or allergic in nature. The clinical presentation may vary depending on the identity of the triggering agent and the reactivity of the subject, but in all cases the lesions are primarily confined to the site of contact. According to the mechanism of elicitation, the following types of contact reactions may be distinguished: (1) allergic contact dermatitis (ACD); (2) irritant contact dermatitis (ICD); (3) phototoxic and photoallergic contact dermatitis, and (4) immediate type contact reactions. The present review will focus on allergic contact dermatitis. ACD is the clinical presentation of contact sensitivity in humans. The pathophysiology of the contact sensitivity reaction has been reviewed in a preceding issue of this journal [1].

Cytotoxicity is mandatory for CD8(+) T cell-mediated contact hypersensitivity

Contact hypersensitivity (CHS) is a T cell-mediated skin inflammation induced by epicutaneous exposure to haptens in sensitized individuals. We have previously reported that CHS to dinitrofluorobenzene in mice is mediated by major histocompatibility complex (MHC) class I-restricted CD8(+) T cells. In this study, we show that CD8(+) T cells mediate the skin inflammation through their cytotoxic activity. The contribution of specific cytotoxic T lymphocytes (CTLs) to the CHS reaction was examined both in vivo and in vitro, using mice deficient in perforin and/or Fas/Fas ligand (FasL) pathways involved in cytotoxicity. Mice double deficient in perforin and FasL were able to develop hapten-specific CD8(+) T cells in the lymphoid organs but did not show CHS reaction. However, they did not generate hapten-specific CTLs, demonstrating that the CHS reaction is dependent on cytotoxic activity. In contrast, Fas-deficient lpr mice, FasL-deficient gld mice, and perforin-deficient mice developed a normal CHS reaction and were able to generate hapten-specific CTLs, suggesting that CHS requires either the Fas/FasL or the perforin pathway. This was confirmed by in vitro studies showing that the hapten-specific CTL activity was exclusively mediated by MHC class I-restricted CD8(+) T cells which could use either the perforin or the Fas/FasL pathway for their lytic activity. Thus, cytotoxic CD8(+) T cells, commonly implicated in the host defence against tumors and viral infections, could also mediate harmful delayed-type hypersensitivity reactions.

Relief of a repressed gene expression state in the mouse 1-cell embryo requires DNA replication

In the mouse, transcriptional permissiveness is established in the fertilized egg prior to the activation of zygotic genes at the 2-cell stage. Therefore, gene inactivity initiated at the end of gametogenesis results from a complex process, involving more than an inhibition of the basal transcriptional apparatus. We have examined the ability of the first intron (I1) of the human hypoxanthine phosphoribosyl transferase gene, which functions as an enhancer in embryonic stem cells, to activate a reporter gene when placed proximally to or at a distance from the HSV-tk promoter, or when integrated into the mouse genome as part of a stable transgene. In microinjected embryos, I1 functions as an enhancer sequence; however, its competence for long-range activation appears only after the late 1-cell stage and depends on the first DNA replication. Moreover, activation of microinjected transgenes from proximal enhancers occurs in the late 2-cell embryo and in the male pronucleus of 1-cell embryos blocked for DNA replication; whereas, for integrated transgenes, proximal enhancer activity is subject to position effects in the 2-cell embryo and first occurs at the 2- or 4-cell stage, but only after completion of DNA replication. Therefore, the absence of long-range activation and a non-permissive genomic state (the relief of which both depend on DNA replication), together with an inactive transcriptional apparatus, appear to converge to prevent any gene activity in the 1-cell embryo. We propose that the embryo exploits the process of DNA replication to relieve the transcriptionally repressive state that was initially established to fulfil two purposes: (1) to arrest maternal gene expression in the maturing oocyte and (2) to protect the unicellular egg and 1-cell embryo from premature differentiation. Reactivation of gene expression by DNA replication would therefore serve to coordinate cell proliferation and differentiation in the preimplantation embryo.

[Physiopathology of eczema]

Eczema is a skin inflammatory reaction mediated by antigen-specific T cells. Two main disorders belong to this group: contact dermatitis and atopic dermatitis. The pathophysiological mecanisms involved in both disorders are similar and include, at the cellular level, three elements: the antigen (hapten or environmental antigen), antigen-presenting cells belonging to the group of dendritic cells and antigen-specific T cells. The Langerhans cell responsible for antigen handling and presentation to specific T cells appears to play a central role for the generation of the inflammatory reaction.