T cell Vbeta repertoires in childhood vasculitides

Mycophenolate Mofetil Versus Cyclophosphamide for Remission Induction in Childhood Polyarteritis Nodosa: An Open-Label, Randomized, Bayesian Noninferiority Trial

OBJECTIVE

Cyclophosphamide (CYC) is used in clinical practice off-label for the induction of remission in childhood polyarteritis nodosa (PAN). Mycophenolate mofetil (MMF) might offer a less toxic alternative. This study was undertaken to explore the relative effectiveness of CYC and MMF treatment in a randomized controlled trial (RCT).

METHODS

This was an international, open-label, Bayesian RCT to investigate the relative effectiveness of CYC and MMF for remission induction in childhood PAN. Eleven patients with newly diagnosed childhood PAN were randomized (1:1) to receive MMF or intravenous CYC; all patients received the same glucocorticoid regimen. The primary end point was remission within 6 months while compliant with glucocorticoid taper. Bayesian distributions for remission rates were established a priori for MMF and CYC by experienced clinicians and updated to posterior distributions on trial completion.

RESULTS

Baseline disease activity and features were similar between the 2 treatment groups. The primary end point was met in 4 of 6 patients (67%) in the MMF group and 4 of 5 patients (80%) in the CYC group. Time to remission was shorter in the MMF group compared to the CYC group (median 7.1 weeks versus 17.6 weeks). No relapses occurred in either group within 18 months. Two serious infections were found to be likely linked to MMF treatment. Physical and psychosocial quality-of-life scores were superior in the MMF group compared to the CYC group at 6 months and 18 months. Combining the prior expert opinion with results from the present study provided posterior estimates of remission of 71% for MMF (90% credibility interval [90% CrI] 51, 83) and 75% for CYC (90% CrI 57, 86).

CONCLUSION

The present results, taken together with prior opinion, indicate that rates of remission induction in childhood PAN are similar with MMF treatment and CYC treatment, and MMF treatment might be associated with better health-related quality of life than CYC treatment.

Update on association between Kawasaki disease and infection

The relationship between infection and Kawasaki disease (KD) remains unclear. Infection has long been considered a key predisposing factor for KD. Bacterial and viral agents may be related to the onset of KD because of superantigen and cytokine production. Various bacterial and viral infections have been reported to be associated with KD, but the actual mechanism remains unknown. The higher association between KD and enterovirus has been well documented by using Taiwan National Health Insurance Research Database. However, no evidence has been obtained that various bacterial and viral infections induce KD. Comprehensive research, including infectious agents, should be conducted to elucidate the pathogenesis of KD.

Distribution of distinct subsets of circulating T follicular helper cells in Kawasaki disease

Background

Kawasaki disease (KD) is an acute febrile vasculitis that primarily affects children. Previous studies have shown that both innate and adapt immune systems are involved in the immunopathogenesis of KD. The following study analyzes the distribution of the subsets of Circulating T follicular helper cells (cTfh cells) in KD patients with and without coronary artery lesions (CALs).

Methods

Twenty KD patients and fifteen healthy sex- and age- matched children were enrolled. Patients were divided into two groups depending on CALs. Blood samples were collected respectively before and after intravenous immunoglobulin (IVIG) administration. Circulating Tfh cells were categorized into three subsets by flow cytometry including cTfh1 (CXCR3 + CCR6-), cTfh2 (CXCR3-CCX6-) and cTfh17 (CXCR3-CCR6+) cells in circulating CD3 + CD4 + CXCR5 + CD45RA- T cells. Cytometric bead arrays were used to analyze the level of IFN-γ, IL-4 and IL-17A.

Results

We found that frequency of cTfh2 cells was significantly elevated in KD patients before IVIG administration with low expression of cTfh1 cells, where the ratio of cTfh2 + cTfh17/cTfh1 significantly increased. Levels of IFN-γ, IL-4 and IL-17A in KD were significantly higher compared to controls. Further analysis showed that cTfh1 cells were negatively correlated with serum CRP, whereas cTfh2 cells were positively correlated with serum CRP and ESR. Comparison of different groups showed that frequency of cTfh1 cells in CALs+ group were significantly lower compared to CALs- group. In contrast, cTfh2 cells in CALs+ group significantly increased. After IVIG administration, frequency of cTfh2 cells and the ratio significantly decreased while the frequency of cTfh1 cells significantly increased. Meanwhile, all levels of cytokines decreased.

Conclusions

Our data demonstrated that cTfh1 and cTfh2 cells participate in the pathogenesis of KD, and that the two subsets might be associated with CALs.

Variation in IL-21-secreting circulating follicular helper T cells in Kawasaki disease

Objective

Circulating follicular helper T (cTfh) cells are a specialized subset of CD4⁺ T cells that express the CXC-chemokine receptor 5 (CXCR5). These cells exhibit immune activities by inducing B cell differentiation and proliferation via the secretion of interleukin (IL)-21. Multiple studies have demonstrated that cTfh cells are associated with the progression and severity of numerous diseases. To investigate the role of cTfh cells in the development of Kawasaki disease (KD), we analyzed the distinct subpopulations of cTfh cells and serum IL-21 levels in different phases of KD.

Methods

According to the differential expression of inducible co-stimulator (ICOS) and programmed cell death protein 1 (PD-1), cTfh cells were divided into distinct subsets. We used flow cytometry and flow cytometric bead arrays (CBA) to analyze subsets of CD4⁺CXCR5⁺ T cells and serum IL-21 levels. The samples were collected from control subjects and Kawasaki disease patients in the acute and remission phases.

Results

In the acute phase (AP), the percentages of ICOS^highPD-1^high, ICOS⁺PD-1⁺, ICOS⁻PD-1⁺, CD45RA⁻IL-21⁺ cTfh cells and serum IL-21 levels significantly increased. Furthermore, the percentages of ICOS^highPD-1^high and ICOS⁺PD-1⁺ cTfh cells positively correlated with erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) values, whereas the percentage of ICOS⁻PD-1⁺ cTfh cells indicated negative correlations. The percentages of ICOS⁺PD-1⁺, ICOS^highPD-1^high and CD45RA⁻IL-21⁺ cTfh cells correlated positively with serum IL-21 levels. In the remission phase (RP), the percentages of ICOS⁻PD-1⁺, CD45RA⁻IL-21⁺ cTfh cells and serum IL-21 levels were significantly decreased. In contrast, the percentages of ICOS⁺PD-1⁺, ICOS^highPD-1^high, and ICOS⁺PD-1⁻ cTfh cells were further increased. Among these subsets, only CD45RA⁻IL-21⁺ cTfh cells correlated positively with serum IL-21 levels.

Conclusions

The present study is the first investigation that examined the distribution of circulating cTfh cell subsets in Kawasaki disease. Both cTfh cells and serum IL-21 are essential to the pathogenesis of KD. Our study provides further understanding of the immune response involved in KD and offers novel insights in the pathogenetic mechanism of this disease.

Electronic supplementary material

The online version of this article (10.1186/s12865-018-0282-8) contains supplementary material, which is available to authorized users.

Isolation of vascular smooth muscle antigen-reactive CD4(+)αβTh1 clones that induce pulmonary vasculitis in MRL/Mp-Fas(+/+) mice

Here, we established CD4(+)αβTh1 clones specific for rat vascular smooth muscle antigen (VSMAg) that induced vasculitis lesions in the lungs of MRL/Mp-Fas(+/+) mice following adoptive transfer. Six different T cell clones, MV1b1 (Vβ1), MV1b4 (Vβ4), MV1b8.3 (Vβ8.3), MV1b61 (Vβ6), MV1b62 (Vβ6), and MV1b63 (Vβ6), were isolated from the MV1 T cell line from the regional lymph nodes of immunized MRL/Mp-Fas(+/+) mice; the three (Vβ6) clones had unique CDR3 amino acid sequences. Following stimulation with VSMAg-pulsed antigen presenting cells, MV1b61 and MV1b62 failed to secrete interferon-γ and tumor necrosis factor-α, although the other four clones secreted high levels of both cytokines. In adoptive transfer experiments, MV1b61 and MV1b62 did not induce organ involvement including pulmonary vasculitis. In contrast, MV1b1, MV1b4, MV1b8.3, and MV1b63 induced perivascular mononuclear cell infiltration in pulmonary small arteries. These clones may provide useful tools for investigating the underlying mechanisms of vasculitis syndromes and for developing therapeutic strategies.

T-cell receptor phenotype pattern in atopic children using commercial fluorescently labeled antibodies against 21 human class-specific v segments for the tcrβ chain (vβ) of peripheral blood: a cross sectional study

BACKGROUND

T-cell receptor (TCR) repertoire development is an integral part of the adaptive immune response. T-cell activation requires recognition of appropriately processed antigens by the TCR. Development of a diverse repertoire of TCRs is therefore essential to ensure adequate protection from potential threats. The majority of T-cells in peripheral blood have TCRs composed of an alpha and a beta chain. At the DNA level, the TCR genes are formed through directed recombination from germline sequences-the so-called VDJ recombination [variable (V) joining (J) diversity (D) gene segments] which results in variations in the repertoire. The most variable part of TCRs is the Vβ region (VβTCR), which has multiple V segment families that can be quantitatively measured. However, only sparse data exists on the normal levels of the VβTCR repertoire in healthy children. We aimed to establish normal values for the VβTCR repertoire in atopic children without immunodeficiency.

METHODS

Fifty-three children were recruited from food allergy, drug allergy, chronic urticaria and anaphylaxis registries and were divided into groups based on age: >0-2 years, 3-6 years, and 6-18 years. We used commercially available and fluorescently labeled antibodies against 21 human class-specific V segments of the TCRβ chain (Vβ) to study in peripheral blood the quantitative pattern of Vβ variation by flow cytometry.

RESULTS

Children of all ages exhibited a similar pattern of TCR Vβ expression. Vβ 2 was the most commonly expressed family in all three age groups [9.5 % (95 % CI, 8.9, 10 %), 8.8 % (95 % CI, 7.4, 10.2 %) and 7.6 % (7.0, 8.3 %) respectively]. However, the percentage of Vβ 2 decreased in older children and the percentage of Vβ 1 was higher in males. TCR Vβ expression in our sample of atopic children did not differ substantially from previously published levels in non-atopic cohorts.

CONCLUSION

TCR Vβ diversity follows a predictable and comparable pattern in atopic and healthy non-atopic children. Establishing normal levels for healthy children with and without atopy will contribute to a better definition of Vβ receptor deviation in children with primary immunodeficiency and/or immunodysregulation conditions.

Mild forms of toxic shock syndrome toxin-1-mediated exanthematous disease related to Staphylococcus aureus infection

The present report describes three patients with toxic shock syndrome toxin (TSST)-1-associated exanthematous disease. In all patients, fever and systemic erythema without hemodynamic disturbance occurred following cellulitis of the lower limbs. At the site of infection, TSST-1 producing Methicillin-susceptible Staphylococcus aureus was detected. They defervesced and erythema resolved in response to administration of an antimicrobial drug, thereby avoiding severe illness. These patients did not meet the criteria for a clinical diagnosis of toxic shock syndrome. Measurement of T-cell receptor Vβ2-positive T cells in the peripheral blood early after onset of symptoms was useful for diagnosis.

The molecular and functional characterization of clonally expanded CD8+ TCR BV T cells in eosinophilic granulomatosis with polyangiitis (EGPA)

In eosinophilic granulomatosis with polyangiitis (EGPA) clonally expanded T cells might concur in granuloma formation and vascular injury. The TCR β-variable (BV) chain repertoire and third complementarity determining region (CDR3) of peripheral CD4+ and CD8+ cells in EGPA patients and age-matched controls and the expression of cytokines and chemokine receptors were investigated. The CD8+ lymphocytes of EGPA patients showed an increased frequency of BV expansions with a skewed profile of BV CDR3 lengths, increased CCR5 and CXCR3 expression and increased INFγ and TNFα production. In two patients, the TCR CDR3 cDNA sequences of the expanded BV family were identified. The CD4+ lymphocytes of EGPA patients revealed a higher expression of CRTH2 and increased production of IL-5. In conclusion, CD4+ T cells display a Th2 profile and CD8+ T cells are clonally expanded in EGPA and have a proinflammatory phenotype, suggesting their pathogenic role in vasculitic damage.

Update on Kawasaki disease: epidemiology, aetiology and pathogenesis

Kawasaki disease is an acute systemic vasculitis predominantly affecting young children. It is due to an abnormal host response to as yet unidentified infectious trigger(s). Kawasaki disease may cause coronary artery damage, long-term cardiovascular morbidity and occasionally mortality, especially if the diagnosis is missed or timely treatment is not given. This is the first of two updates on Kawasaki disease. Here we review recent advances in epidemiology, possible aetiologies, host susceptibility and pathogenesis of this fascinating condition.

Flow cytometric analysis of the CD4+ TCR Vβ repertoire in the peripheral blood of children with type 1 diabetes mellitus, systemic lupus erythematosus and age-matched healthy controls

BACKGROUND

Data regarding the quantitative expression of TCR Vβ subpopulations in children with autoimmune diseases provided interesting and sometimes conflicting results. The aim of the present study was to assess by comparative flow cytometric analysis the peripheral blood CD4+ TCR Vβ repertoire of children with an organ-specific autoimmune disorder, such as type 1 diabetes mellitus (T1DM), in comparison to children with a systemic autoimmune disease, such as Systemic Lupus Erythematosus (SLE) in comparison to healthy age-matched controls of the same ethnic origin. The CD4+ TCR Vβ repertoire was analysed by flow cytometry in three groups of participants: a) fifteen newly diagnosed children with T1DM (mean age: 9.2 ± 4.78 years old), b) nine newly diagnosed children with SLE, positive for ANA and anti-dsDNA, prior to treatment (mean age: 12.8 ±1.76 years old) and c) 31 healthy age-matched controls (mean age: 6.58 ± 3.65 years old), all of Hellenic origin.

RESULTS

CD4 + TCR Vβ abnormalities (± 3SD of controls) were observed mainly in SLE patients. Statistical analysis revealed that the CD4 + Vβ4 chain was significantly increased in patients with T1DM (p < 0.001), whereas CD4 + Vβ16 one was significantly increased in SLE patients (p < 0.001) compared to controls.

CONCLUSIONS

CD4 + Vβ4 and CD4 + Vβ16 chains could be possibly involved in the cascade of events precipitating the pathogenesis of T1DM and SLE in children, respectively.

Kawasaki disease in ghana: case reports from Korle Bu teaching hospital

Kawasaki disease, an acute febrile vasculitis, predominantly affects children under the age of 5 years and is thought to be a rare disease in the developing world. It has previously never been reported in Ghana. We report 3 cases from February, 2007 to February, 2008. This potentially serious disease has no definitive diagnostic test and it is not unusual for diagnosis to be delayed with serious consequences. Any child with irritability and persisting fever (>5 days) not responding to antipyretics and antibiotics, accompanied by a rash and non purulent conjunctivitis should be suspected to have Kawasaki disease.

Mycobacterium tuberculosis culture filtrate protein 10-specific effector/memory CD4⁺ and CD8⁺ T cells in tubercular pleural fluid, with biased usage of T cell receptor Vβ chains

T cell-mediated immunity is critical for the control of Mycobacterium tuberculosis infection. Identifying the precise immune mechanisms that lead to control of initial M. tuberculosis infection and preventing reactivation of latent infection are crucial for combating tuberculosis. However, a detailed understanding of the role of T cells in the immune response to infection has been hindered. In addition, there are few flow cytometry studies characterizing the Vβ repertoires of T cell receptors (TCRs) at local sites of M. tuberculosis infection in adult tuberculosis. In this study, we used culture filtrate protein 10 (CFP-10) from M. tuberculosis to characterize T cells at local sites of infection. We simultaneously analyzed the correlation of the production of cytokines with TCR Vβ repertoires in CFP-10-specific CD4(+) and CD8(+) T cell subsets. For the first time, we demonstrate that CFP-10-specific CD4(+) or CD8(+) T cells from tubercular pleural fluid can produce high levels of gamma interferon (IFN-γ) and tumor necrosis factor alpha (TNF-α) and upregulate the expression of CD107a/b on the cell surface. The CFP-10-specific cells were effector/memory cells with a CD45RO(+) CD62L(-) CCR7(-) CD27(-) expression profile. In addition, we found CFP-10-specific CD4(+) and CD8(+) T cells in tubercular pleural fluid, with biased usage of TCR Vβ9, Vβ12, or Vβ7.2. Our findings of CFP-10-specific CD4(+) and CD8(+) T cells in tubercular pleural fluid are critical for understanding the mechanisms of the local cellular immune response and developing more effective therapeutic interventions in cases of M. tuberculosis infection.

Medium-size-vessel vasculitis

Medium-size-artery vasculitides do occur in childhood and manifest, in the main, as polyarteritis nodosa (PAN), cutaneous PAN and Kawasaki disease. Of these, PAN is the most serious, with high morbidity and not inconsequential mortality rates. New classification criteria for PAN have been validated that will have value in epidemiological studies and clinical trials. Renal involvement is common and recent therapeutic advances may result in improved treatment options. Cutaneous PAN is a milder disease characterised by periodic exacerbations and often associated with streptococcal infection. There is controversy as to whether this is a separate entity or part of the systemic PAN spectrum. Kawasaki disease is an acute self-limiting systemic vasculitis, the second commonest vasculitis in childhood and the commonest cause of childhood-acquired heart disease. Renal manifestations occur and include tubulointerstitial nephritis and renal failure. An infectious trigger and a genetic predisposition seem likely. Intravenous immunoglobulin (IV-Ig) and aspirin are effective therapeutically, but in resistant cases, either steroid or infliximab have a role. Greater understanding of the pathogenetic mechanisms involved in these three types of vasculitis and better long-term follow-up data will lead to improved therapy and prediction of prognosis.

Efficient characterization of the TCR repertoire in lymph nodes by flow cytometry

Analysis of the T-cell receptor (TCR) repertoire by flow cytometry proved to be relevant for investigating T-cell diversity and detecting reactive cells in blood samples. We used this approach to characterize non-malignant T-lymphocytes in lymph nodes and give insights into their origin. The TCR repertoire of CD4+ and CD8+ T-cells from 81 lymph nodes was analyzed with a four-color flow cytometer using a wide panel of 25 anti-Vbeta monoclonal antibodies. Flow cytometry proved to be a useful and informative technique. We demonstrated a diversified TCR-Vbeta repertoire, and only low level expansions, in 53% of the samples. They involved nearly all Vbeta families, were more frequent in the CD8+ subset of older patients, but were not related to pathology. No evidence could be demonstrated in favor of stimulation by common antigens. Interestingly, the TCR-Vbeta repertoire proved to be very similar in lymph nodes and blood samples. Our results argue that in the cases studied, lymph node enlargement is mainly due to an increased homing of circulating T-cells. They also provide reference values for expression of 25 TCR-Vbeta in lymph nodes, which could serve as a basis for further applications in diagnosis of T-cell lymphoproliferative disorders.

Vasculitis in children

Primary systemic vasculitides of the young are relatively rare diseases, but can have a significant morbidity and mortality. The purpose of this review is to provide an overview of the paediatric vasculitides. Vasculitides that predominantly affect children will be considered in more detail than vasculitic diseases that although are seen in children affect adults more commonly, such as the ANCA associated vasculitides. New classification criteria for childhood vasculitis have recently been proposed and are currently undergoing validation. Epidemiological clues continue to implicate infectious triggers in Kawasaki Disease and Henoch Schönlein purpura. Several genetic polymorphisms have now been described in the vasculitides that may be relevant in terms of disease predisposition or development of disease complications. Treatment regimens continue to improve, with the use of different immunosuppressive medications and newer therapeutic approaches such as biologic agents. However new challenges are looming in regards to the role of inflammation in endothelial health and the long term cardiovascular morbidity for children with primary systemic vasculitis. International multicenter collaboration is of utmost importance in order for us to further advance our understanding and improve the treatment and outcome of systemic vasculitis in the young.

Quantitative detection of circulating endothelial cells in vasculitis: comparison of flow cytometry and immunomagnetic bead extraction

BACKGROUND

Circulating endothelial cells (CECs) are biomarkers for endothelial cell (EC) injury and are quantified using immunomagnetic bead extraction (IBE), or flow cytometry (FC). Reports suggest that there is good agreement between these methods for CEC quantification.

OBJECTIVES

We examined levels of agreement between these techniques in children with systemic vasculitis.

METHODS

We added HUVEC or human pulmonary artery EC to whole blood to optimize FC gating strategies for EC. EC-optimized FC was then compared with IBE for CEC enumeration in 25 children with vasculitis and 20 healthy controls.

RESULTS

Using Bland-Altman analysis, agreement between IBE and EC-optimized FC was poor in children with vasculitis (n = 25) and healthy controls (n = 20): IBE consistently detected higher values than the EC-optimized FC method: the mean difference between the two techniques was 60 CECs mL(-1), 95% CI +/-374 CECs mL(-1) (paired analyses of 45 individuals). Agreement was poorest for vasculitis patients: mean difference (IBE - EC-optimized FC) 120 CECs mL(-1), 95% CI +/-460 CECs mL(-1) (P = 0.018). We identified three reasons for this discrepancy: (i) sub-optimal FC gating parameters previously used for detecting CECs; (ii) inherent lack of sensitivity of FC compared with IBE for CEC rare event detection; and (iii) use of lysis buffers required for FC causing CEC lysis.

CONCLUSIONS

There was poor agreement between EC-optimized FC and IBE for the quantification of CECs from children with active vasculitis and controls. We emphasize that in this clinical setting the two techniques are not directly comparable when comparing results obtained using these different methodologies.

Clonal CD8+ TCR-Vbeta expanded populations with effector memory phenotype in Churg Strauss syndrome

Churg Strauss Syndrome (CSS) is a systemic vasculitis in which oligoclonal T cell expansions might be involved in the pathogenesis. Combined analysis of TCR-Vbeta expression profile by flow cytometry and of TCR gene rearrangement by heteroduplex PCR was used to detect and characterize T cell expansions in 8 CSS patients, 10 asthmatics and 42 healthy subjects. In all CSS patients one or two Vbeta families were expanded among CD8+ cells, with an effector memory phenotype apt to populate tissues and inflammatory sites. Heteroduplex PCR showed the presence of one or more clonal TCR rearrangements, which reveals monoclonal or oligoclonal T cells subpopulations. After purification with a Vbeta specific monoclonal antibody, each CD8+/Vbeta+ expanded family showed a single TCR rearrangement, clearly suggestive of monoclonality. All CD8+ expansions were detectable throughout the disease course. TCR-Vbeta expanded or deleted populations were not observed in asthmatic patients. Clonal CD8+/Vbeta+ T cell expansions might be useful as a disease marker.

HLA class II transgenic mice mimic human inflammatory diseases

Population studies have shown that among all the genetic factors linked with autoimmune disease development, MHC class II genes on chromosome 6 accounts for majority of familial clustering in the common autoimmune diseases. Despite the highly polymorphic nature of HLA class II genes, majority of autoimmune diseases are linked to a limited set of class II-DR or -DQ alleles. Thus a more detailed study of these HLA-DR and -DQ alleles were needed to understand their role in genetic predisposition and pathogenesis of autoimmune diseases. Although in vitro studies using class-II restricted CD4 T cells and purified class II molecules have helped us in understanding some aspects of HLA class-II association with disease, it is difficult to study the role of class II genes in vivo because of heterogeneity of human population, complexity of MHC, and strong linkage disequilibrium among different class II genes. To overcome this problem, we pioneered the generation of HLA-class II transgenic mice to study role of these molecule in inflammatory disease. These HLA class II transgenic mice were used to develop novel in vivo disease model for common autoimmune diseases such as rheumatoid arthritis, multiple sclerosis, insulin-dependent diabetes mellitus, myasthenia gravis, celiac disease, autoimmune relapsing polychondritis, autoimmune myocarditis, thyroiditis, uveitis, as well as other inflammatory disease such as allergy, tuberculosis and toxic shock syndrome. As the T-cell repertoire in these humanized HLA transgenic mice are shaped by human class II molecules, they show the same HLA restriction as humans, implicate potential triggering mechanism and autoantigens, and identify similar antigenic epitopes seen in human. This review describes the value of these humanized transgenic mice in deciphering role of HLA class II molecules in immunopathogenesis of inflammatory diseases.

T cell activation profiles in Kawasaki syndrome

Superantigens (SAgs) are potent stimulators of T cells bearing specific Vbeta T cell receptors (TCR) and may play a role in the pathogenesis of Kawasaki syndrome (KS), although despite 15 years of intense study this area remains controversial. Because SAgs can cause Vbeta restricted T cell activation in the absence of Vbeta skewing the aims of this study were to describe a flow cytometric protocol to study both CD4 and CD8 Vbeta repertoires, and CD69 expression across the CD4 and CD8 Vbeta repertoire in children with KS. Sixteen children with KS were studied. There was no significant increase in overall peripheral blood CD4 or CD8 T cell activation as determined by CD69 expression. However, Vbeta restricted CD4 and/or CD8 activation was observed in eight of 11 (72%) of the KS patients, a finding not observed in healthy controls. Thirteen of 16 (81%) of the KS patients had evidence of either Vbeta skewing (particularly CD4 Vbeta2 and Vbeta5.1) and/or Vbeta restricted activation. Three patients had Vbeta restricted activation in the absence of skewing. We suggest that these preliminary observations highlight the many layers of complexity when considering T cell activation in KS, which could explain some of the conflicting studies regarding peripheral blood T cell activation and Vbeta skewing. It is likely that in order to move forward with this debate a combination of detailed microbiological, immunological and molecular techniques applied to individual patients will be required ultimately to prove or refute the SAg hypothesis of KS.

Vasculitis in children

Vasculitis is rare in children, and, apart from HSP and perhaps KD, most practicing pediatricians will never encounter a case. Nonetheless, progress in the diagnosis and treatment of these conditions has afforded most children with vasculitis a reasonably good prognosis. Accordingly, it is important to consider vasculitis as a potential cause of unexplained inflammation, perplexing rashes, or strange combinations of symptoms. Although evaluation and management of suspected vasculitis are difficult in the best of situations, they are impossible if the diagnosis is not considered.

The role of superantigens of group A Streptococcus and Staphylococcus aureus in Kawasaki disease

PURPOSE OF REVIEW

Since the first suggestion of a superantigen hypothesis for Kawasaki disease over a decade ago, debate on the aetiology remains inconclusive. This article reviews recent publications that address the role of superantigens of group A Streptococcus and Staphylococcus aureus in the pathogenesis of Kawasaki disease.

RECENT FINDINGS

Over the past few years, new superantigens produced by group A Streptococcus and S. aureus have been increasingly identified, bringing the total known number to more than 30. Several studies on T-cell Vbeta repertoires and seroloepidemiology have demonstrated evidence for the involvement of single or multiple superantigens produced by the two pathogens. The associated superantigens differed in those studies, including streptococcal pyrogenic toxins A and C, staphylococcal enterotoxins A-C, and toxic shock syndrome toxin 1. These disparate findings suggest that the inflammation of Kawasaki disease does not result from a single agent but rather a final common inflammatory pathway in genetically susceptible individuals after numerous infectious agents.

SUMMARY

Certain staphylococcal and streptococcal superantigens are suggested to be responsible for the development of Kawasaki disease. A better understanding of the precise role of the causative agents will lead to accurate diagnosis, more targeted therapy and an improvement of coronary outcomes.

Kawasaki disease: diagnosis, management and cardiac sequelae

Kawasaki disease (KD) is an acute self-limiting systemic vasculitis of unknown etiology and the most common cause of acquired coronary disease in children aged 6 months to 5 years. The inflammatory process results in coronary arteritis, aneurysmal lesions, arterial thrombotic occlusion or even sudden death. The diagnostic tests are unknown but treatment with immunoglobulin and aspirin is effective at reducing cardiac complications from 25 to 4.7% in the UK. Myocardial, endocardial or pericardial inflammation may occur acutely or many years later and abnormalities of myocardial blood flow may require ongoing medication, interventional catheterization or even cardiac surgery. There are several new drugs that may have important roles to play in managing KD in children and young adults.

What's new in the aetiopathogenesis of vasculitis?

The cause of the majority of childhood vasculitides is unknown although it is likely that a complex interaction between environmental factors and inherited host responses trigger the disease and determine the vasculitis phenotype. Epidemiological clues continue to implicate infectious triggers in Kawasaki syndrome (KS) and Henoch Schonlein purpura (HSP). Several genetic polymorphisms have now been described in KS and HSP which predispose to disease or predict disease severity. Anti-neutrophil cytoplasmic antibodies (ANCA) are now known to be directly involved in the pathogenesis of vascular injury in ANCA-associated vasculitides, although why some individuals develop ANCA in the first instance is not yet understood. Endothelial injury and repair are active areas of research in vasculitis. It is now possible to track endothelial injury non-invasively in children with vasculitis using surrogate markers of endothelial injury. The vasculogenic pathways involved in vascular repair following vasculitis, including endothelial progenitor cells, are beginning to be studied. It is anticipated that an improved understanding of the aetiopathogenesis of vasculitis in the young will ultimately shape future novel diagnostic and therapeutic approaches and will help us predict which children may develop premature arteriosclerosis in later life.

Cutaneous Vasculitis Update: Diagnostic Criteria, Classification, Epidemiology, Etiology, Pathogenesis, Evaluation and Prognosis

Vasculitis, inflammation of the vessel wall, can result in mural destruction with hemorrhage, aneurysm formation, and infarction, or intimal-medial hyperplasia and subsequent stenosis leading to tissue ischemia. The skin, in part due to its large vascular bed, exposure to cold temperatures, and frequent presence of stasis, is involved in many distinct as well as un-named vasculitic syndromes that vary from localized and self-limited to generalized and life-threatening with multi-organ disease. To exclude mimics of vasculitis, diagnosis of cutaneous vasculitis requires biopsy confirmation where its acute signs (fibrinoid necrosis), chronic signs (endarteritis obliterans), or past signs (acellular scar of healed arteritis) must be recognized and presence of extravascular findings such as patterned fibrosis or collagenolytic granulomas noted. Although vasculitis can be classified by etiology, many cases have no identifiable cause, and a single etiologic agent can elicit several distinct clinicopathologic expressions of vasculitis. Therefore, the classification of cutaneous vasculitis is best approached morphologically by determining vessel size and principal inflammatory response. These histologic patterns roughly correlate with pathogenic mechanisms that, when coupled with direct immunofluorescent examination, anti-neutrophil cytoplasmic antibody (ANCA) status, and findings from work-up for systemic disease, allow for specific diagnosis, and ultimately, more effective therapy. Herein, we review cutaneous vasculitis focusing on diagnostic criteria, classification, epidemiology, etiology, pathogenesis, and evaluation of the cutaneous vasculitis patient.

Immunological profile of peripheral blood lymphocytes and monocytes/macrophages in Kawasaki disease

Kawasaki disease (KD) is an acute illness of early childhood characterized by prolonged fever, diffuse mucosal inflammation, indurative oedema of the hands and feet, a polymorphous skin rash and nonsuppurative lymphadenopathy. The histopathological findings in KD comprise panvasculitis with endothelial necrosis, and the infiltration of mononuclear cells into small and medium-sized blood vessels. The levels of many proinflammatory cytokines, chemokines and adhesion molecules can be elevated in sera from children with KD at the acute stage. Although many immunological studies on KD involving peripheral blood have been reported, the data obtained remain controversial. This review focuses on the immune response of peripheral blood lymphocytes and monocytes/macrophages during acute KD.

Vasculitis in children

This article provides a general overview of vasculitis, situations in which the diagnosis should be considered, diagnostic methods, and therapeutic considerations. Details and treatments unique to specific vasculitides are also reviewed.

Coronary artery changes in patients with Kawasaki disease

Kawasaki disease (KD) is an acute, self-limiting, systemic vasculitis of unknown aetiology, which most commonly occurs in children aged 6 mo to 5 y, with a peak incidence at 9-11 mo. The inflammatory process preferentially involves the coronary arteries, potentially resulting in coronary arteritis, aneurysmal lesions, arterial thrombotic occlusion and sudden death. Kawasaki disease is the most common cause of acquired coronary vessel abnormalities in children. The cause of KD is not known, but evidence is presented for an inflammatory response and a genetic predisposition. The diagnostic tests are not yet defined, but treatment with immunoglobulin and aspirin is effective at reducing the risk of cardiac complications from 25% to 4.7% in the UK. Sequelae may occur, either acutely with myocardial, endocardial or pericardial inflammation, or many years after the original illness. There may be abnormalities of myocardial blood flow as assessed by MRI, radio-nucleide studies or echo Doppler. Such abnormalities of coronary arteries may require ongoing medication, interventional catheterization or even cardiac surgery. In the future, we hope to have more accurate diagnostic tests or prophylaxis against the disease, in addition to improved means of determining the susceptibility to or presence of long-term complications.

Update on childhood vasculitides

PURPOSE OF REVIEW

The purpose of this review is to provide an update on the new developments in pediatric vasculitis.

RECENT FINDINGS

Because most childhood vasculitides are rare, few large systematic studies have been done. Studies of Henoch-Schönlein purpura have focused on pathogenesis and outcome. Genetic associations and molecular changes occurring during Henoch-Schönlein purpura, including cytokines, and endothelial and nitric oxide metabolism are discussed. Risk factors for renal involvement and poor renal outcome are described. Uncontrolled series of treatment protocols for severe Henoch-Schönlein purpura nephritis are mentioned. Several studies have focused on the pathogenesis of other primary vasculitides, especially polyarteritis nodosa. Series describing the clinical manifestations of childhood vasculitis and case reports of uncommon manifestations of vasculitis in children are presented. The efficacy of new therapies, including the use of thalidomide and biologic modifiers, has been shown in individual childhood cases; however, there are no controlled studies of these agents.

SUMMARY

Besides studies of Henoch-Schönlein purpura, advances in pediatric vasculitis are few as a result of the rarity of most vasculitides in childhood. Multicenter collaboration is necessary to substantially increase the scientific base of investigating and treating childhood vasculitis.

Kawasaki disease and toxic shock syndrome--at last the etiology is clear?

A decade after the superantigen hypothesis for KD was first suggested, it has still not been either proven or refuted conclusively. Although initial optimism for the hypothesis was quashed by a series of published papers apparently refuting the idea, in the last few years there have been a number of good studies providing evidence in support of the superantigen hypothesis. Whether this renewed enthusiasm is justified will hopefully become clear in the near future. Ultimately, accurate diagnosis, more targeted treatment, and preventative strategies depend on the unraveling of the immunopathogenesis of this disease.

Vbeta-restricted T cell adherence to endothelial cells: a mechanism for superantigen-dependent vascular injury

OBJECTIVE

To investigate the potential for endothelial cells to operate as superantigen-presenting cells for T cells and the potential for such an interaction to cause endothelial cell activation and injury.

METHODS

Class II major histocompatibility complex (MHC)-positive human umbilical vein endothelial cells (HUVECs) were cocultured for 4 hours with purified T cells and the superantigens staphylococcal enterotoxin B (SEB) or toxic shock syndrome toxin 1 (TSST-1). After staining with fluorescence-conjugated monoclonal antibodies, flow cytometric analysis was performed on the HUVECs and T cells to examine V(beta)-restricted T cell adherence to the endothelial cell monolayer, V(beta)-restricted T cell activation (CD69 up-regulation), surface expression of endothelial cell activation markers, and generation of endothelial microparticles (EMPs).

RESULTS

Coculture of purified T cells with class II MHC-positive HUVECs and either TSST-1 or SEB resulted in V(beta)-restricted CD69 up-regulation by CD4 and CD8 cells (V(beta)2 activation for TSST-1; V(beta)3, V(beta)5.1, and V(beta)12 activation for SEB). Additionally, there was CD4 and CD8 T cell V(beta)-restricted adherence to the HUVEC monolayer at 4 hours. Expression of intercellular adhesion molecule 1, E-selectin, and vascular cell adhesion molecule 1 was up-regulated on the class II MHC-positive HUVECs following exposure to superantigen in the presence of T cells, and there was increased EMP release from activated HUVECs, which occurred earlier and was of greater magnitude than that observed in response to tumor necrosis factor alpha.

CONCLUSION

Class II MHC-positive endothelial cells operate as competent superantigen-presenting cells for CD4 and CD8 lymphocytes in vitro. Dual signaling between endothelial cells and T cells results in V(beta)-restricted activation and adherence to endothelial monolayers and endothelial cell activation and release of EMPs expressing inducible cell adhesion molecules. It is proposed that this mechanism could account in part for the vascular injury associated with superantigen-mediated diseases including Kawasaki disease.

Endothelial and platelet microparticles in vasculitis of the young

OBJECTIVE

Microparticles are released from endothelial cells in response to a variety of injurious stimuli and recently have been shown to be increased in a number of diseases associated with endothelial dysfunction. This study examined endothelial microparticle (EMP) and platelet microparticle (PMP) profiles in children with systemic vasculitis to test the hypothesis that EMPs may provide a noninvasive means of examining endothelial activation or injury.

METHODS

The study cohort comprised 39 children with systemic vasculitis at various stages of disease activity, 24 control children with febrile disease, and a control group of 43 healthy subjects. Plasma was ultracentrifuged at 17,000g for 60 minutes, and the microparticle pellets were examined using flow cytometry.

RESULTS

Plasma from patients with active systemic vasculitis contained significantly higher numbers of E-selectin-positive EMPs compared with that from patients in remission, healthy controls, or febrile disease controls (P = 0.000 for each). A similar result was obtained for the numbers of EMPs expressing the marker CD105. There was also a significant increase in PMPs expressing CD42a in the active vasculitis group as compared with the other groups, but this difference was not significant for PMPs expressing P-selectin. The EMP counts correlated with the Birmingham Vasculitis Activity Score and the acute-phase reactant levels in the patients with systemic vasculitis, but there was a poor correlation overall between EMP counts and the acute-phase reactant levels in the febrile disease controls.

CONCLUSION

EMPs may provide a window to the activated endothelium and could provide important pathophysiologic insights into the vascular injury associated with vasculitis of the young.