The meaning of clinical remission in polyarticular juvenile idiopathic arthritis: gene expression profiling in peripheral blood mononuclear cells identifies distinct disease states

OBJECTIVE

The development of biomarkers to predict response to therapy in polyarticular juvenile idiopathic arthritis (JIA) is an important issue in pediatric rheumatology. A critical step in this process is determining whether there is biologic meaning to clinically derived terms such as "active disease" and "remission." The aim of this study was to use a systems biology approach to address this question.

METHODS

We performed gene transcriptional profiling on children who fulfilled the criteria for specific disease states as defined by the consensus criteria developed by Wallace and colleagues. The study group comprised children with active disease (n = 14), children with clinical remission on medication (CRM; n = 9), children with clinical remission off medication (CR; n = 6), and healthy control children (n = 13). Transcriptional profiles in peripheral blood mononuclear cells (PBMCs) were obtained using Affymetrix U133 Plus 2.0 arrays.

RESULTS

Hierarchical cluster analysis and predictive modeling demonstrated that the clinically derived criteria represent biologically distinct states. Minimal differences were seen between children with active disease and those with disease in CRM. Thus, underlying immune/inflammatory abnormalities persist despite a response to therapy. The PBMC transcriptional profiles of children whose disease was in remission did not return to normal but revealed networks of proinflammatory and antiinflammatory genes, suggesting that remission is a state of homeostasis, not a return to a normal state.

CONCLUSION

Gene transcriptional profiling of PBMCs revealed that clinically derived criteria for JIA disease states reflect underlying biology. We also demonstrated that neither CRM nor CR status results in resolution of the underlying inflammatory process, but that these conditions are more likely to be states of balanced homeostasis between proinflammatory and antiinflammatory mechanisms.

Disease-associated pathophysiologic structures in pediatric rheumatic diseases show characteristics of scale-free networks seen in physiologic systems: implications for pathogenesis and treatment

BACKGROUND

While standard reductionist approaches have provided some insights into specific gene polymorphisms and molecular pathways involved in disease pathogenesis, our understanding of complex traits such as atherosclerosis or type 2 diabetes remains incomplete. Gene expression profiling provides an unprecedented opportunity to understand complex human diseases by providing a global view of the multiple interactions across the genome that are likely to contribute to disease pathogenesis. Thus, the goal of gene expression profiling is not to generate lists of differentially expressed genes, but to identify the physiologic or pathogenic processes and structures represented in the expression profile.

METHODS

RNA was separately extracted from peripheral blood neutrophils and mononuclear leukocytes, labeled, and hybridized to genome level microarrays to generate expression profiles of children with polyarticular juvenile idiopathic arthritis, juvenile dermatomyositis relative to childhood controls. Statistically significantly differentially expressed genes were identified from samples of each disease relative to controls. Functional network analysis identified interactions between products of these differentially expressed genes.

RESULTS

In silico models of both diseases demonstrated similar features with properties of scale-free networks previously described in physiologic systems. These networks were observable in both cells of the innate immune system (neutrophils) and cells of the adaptive immune system (peripheral blood mononuclear cells).

CONCLUSION

Genome-level transcriptional profiling from childhood onset rheumatic diseases suggested complex interactions in two arms of the immune system in both diseases. The disease associated networks showed scale-free network patterns similar to those reported in normal physiology. We postulate that these features have important implications for therapy as such networks are relatively resistant to perturbation.

Commentary - ordering lab tests for suspected rheumatic disease

One of the least-appreciated advances in pediatric rheumatology over the past 25 years has been the delineation of the many ways in which children with rheumatic disease differ from adults with the same illnesses. Furthermore, we are now learning that paradigms that are useful in evaluating adults with musculoskeletal complaints have limited utility in children. Nowhere is that more true than in the use of commonly used laboratory tests, particularly antinuclear antibody (ANA) and rheumatoid factor (RF) assays. This short review will provide the practitioner with the evidence base that supports a more limited use of ANA and RF testing in children.

Reduced nicotinamide adenine dinucleotide phosphate oxidase-independent resistance to Aspergillus fumigatus in alveolar macrophages

The fungal pathogen Aspergillus fumigatus is responsible for increasing numbers of fatal infections in immune-compromised humans. Alveolar macrophages (AM) are important in the innate defense against aspergillosis, but little is known about their molecular responses to fungal conidia in vivo. We examined transcriptional changes and superoxide release by AM from C57BL/6 and gp91(phox)(-/-) mice in response to conidia. Following introduction of conidia into the lung, microarray analysis of AM showed the transcripts most strongly up-regulated in vivo to encode chemokines and additional genes that play a critical role in neutrophil and monocyte recruitment, indicating that activation of phagocytes represents a critical early response of AM to fungal conidia. Of the 73 AM genes showing > or = 2-fold changes, 8 were also increased in gp91(phox)(-/-) mice by conidia and in C57BL/6 mice by polystyrene beads, suggesting a common innate response to particulate matter. Ingenuity analysis of the microarray data from C57BL/6 mice revealed immune cell signaling and gene expression as primary mechanisms of this response. Despite the well-established importance of phagocyte NADPH oxidase in resisting aspergillosis, we found no evidence of this mechanism in AM following introduction of conidia into the mouse lung using transcriptional, luminometry, or NBT staining analysis. In support of these findings, we observed that AM from C57BL/6 and gp91(phox)(-/-) mice inhibit conidial germination equally in vitro. Our results indicate that early transcription in mouse AM exposed to conidia in vivo targets neutrophil recruitment, and that NADPH oxidase-independent mechanisms in AM contribute to inhibition of conidial germination.

Brief Report: Illness Intrusiveness and Adjustment among Native American and Caucasian Parents of Children with Juvenile Rheumatic Diseases

OBJECTIVE

To investigate cognitive appraisal-adjustment relationships in Native American (NA) and Caucasian parents of children diagnosed with juvenile rheumatic diseases.

METHODS

NA (n = 16) and Caucasian (n = 24) parents completed measures of disease status, illness intrusiveness, and adjustment; the rheumatologist provided estimates of disease severity.

RESULTS

Hierarchical regression analysis revealed a moderating effect for racial group membership on the illness intrusiveness-parent adjustment relationship. Specifically, parent-perceived illness intrusiveness was more closely related to poorer adjustment among NA parents relative to Caucasian parents. Post hoc tests indicated that illness intrusiveness was significantly associated with poorer adjustment in NA parents, but was unrelated to parent adjustment in the Caucasian sample.

CONCLUSIONS

Results highlight the importance of examining racial group differences in cognitive appraisal-adjustment outcome relationships. Results are discussed with respect to the need for incorporating cultural issues into pediatric chronic illness research and treatment.

Neutrophils: the forgotten cell in JIA disease pathogenesis

Juvenile idiopathic arthritis (JIA) has long been assumed to be an autoimmune disease, triggered by aberrant recognition of "self" antigens by T-cells. However, systems biology approaches to this family of diseases have suggested complex interactions between innate and adaptive immunity that underlie JIA. In particular, new data suggest an important role for neutrophils in JIA pathogenesis. In this short review, we will discuss the new data that support a role for neutrophils in JIA, discuss regulatory functions that link neutrophils to adaptive immune responses, and discuss future areas of investigation. Above all else, we invite the reader to re-consider the use of the term "autoimmunity" as applied to the family of illnesses we collectively call JIA.

A dynamic model of gene expression in monocytes reveals differences in immediate/early response genes between adult and neonatal cells

Neonatal monocytes display immaturity of numerous functions compared with adult cells. Gene expression arrays provide a promising tool for elucidating mechanisms underlying neonatal immune function. We used a well-established microarray to analyze differences between LPS-stimulated human cord blood and adult monocytes to create dynamic models for interactions to elucidate observed deficiencies in neonatal immune responses.

We identified 168 genes that were differentially expressed between adult and cord monocytes after 45 min incubation with LPS. Of these genes, 95% (159 of 167) were over-expressed in adult relative to cord monocytes. Differentially expressed genes could be sorted into nine groups according to their kinetics of activation. Functional modelling suggested differences between adult and cord blood in the regulation of apoptosis, a finding confirmed using annexin binding assays. We conclude that kinetic studies of gene expression reveal potentially important differences in gene expression dynamics that may provide insight into neonatal innate immunity.

Circulating cytokines in Norwegian patients with psoriatic arthritis determined by a multiplex cytokine array system

OBJECTIVES

Serum cytokines play an important role in the pathogenesis of psoriatic arthritis (PsA) by initiating and perpetuating various cellular and humoral autoimmune processes. The aim of this study was to describe a broad spectrum of T- and B-cell cytokines, growth factors and chemokines in patients with PsA and healthy individuals.

METHODS

A novel protein array system, denoted as multiplex cytokine assay was utilized to measure simultaneously the levels of 23 circulating cytokines of patients with PsA and healthy individuals. Additionally, correlational clustering and discriminant function analysis (DFA), two multivariate, supervised analysis methods were employed to identify a subset of biomarkers in order to describe potential functional inter-relationships among these pathological cytokines and identify biomarkers with prognostic and diagnostic utility.

RESULTS

Univariate analysis demonstrated that serum levels of a complex set of immune and inflammatory modulating cytokines are significantly up-regulated in patients with PsA relative to unaffected controls including interleukin (IL)-10, IL-13, interferen (IFN)-alpha, epidermal growth factor (EGF), vascular endothelial growth factor (VEGF), fibroblast growth factor [CCL3 macrophage inflammatory protein (MIP)-1alpha], CCL4 (MIP-1beta) and CCL11 (Eotaxin), while granulocyte-colony stimulating factor was significantly reduced in PsA patients. Correlational clustering was able to discriminate among, and hence subclassify, patients with varying levels of disease activity, which may prove useful in guiding therapy in these apparently phenotypically distinct disease subsets. DFA identified EGF, IFN-alpha, VEGF, CCL3 (MIP-1alpha) and IL-12p40 as analytes with the strongest discriminatory power among various PsA patients and controls.

CONCLUSIONS

Our findings suggest that these factors modulate PsA pathology and the articular involvement in a synergistic manner. Identifying factors could be used in the development of clinical diagnostic tests, which are valuable to guide evidence-based diagnosis and disease management of PsA.

Soluble factors from LPS- and PHA-activated PBMC induce MAPK, Stat1 and Stat3 phosphorylation in primary cultures of human term placental trophoblasts: implications for infection and prematurity

Infection of the maternal vaginal tract is one of the single most important antecedents of premature labor. We have hypothesized that the abundant local synthesis of pro-inflammatory cytokines that occurs during infection may disrupt the delicate "immunological cross-talk" that must occur between maternal and fetal tissues in order to carry pregnancy to term. These experiments were undertaken as part of a larger study directed at testing that hypothesis. We prepared primary cultures of human trophoblasts from term placentas. Cell cultures were stimulated with conditioned medium from resting, PHA or LPS-activated peripheral blood mononuclear cells (PBMC). Medium with LPS or PHA at the same concentration as that used to stimulate the PBMC was used as an additional control. Lysates were subjected to western blotting for activated forms of the mitogen-activated protein kinases (MAPK), Stat1, and Stat3. Western blotting showed phosphorylation of the Jun kinase (JNK), p38, and Erk1/Erk2 MAPK in trophoblasts incubated with conditioned medium from LPS or PHA-activated PBMC but not from medium from resting PBMC, or with PHA or LPS alone. Phosphorylation could be detected as early as 5 min and was still observable by 10 min, the latest time point tested. Similarly, Stat1 and Stat3 phosphorylation was observed within 10 min of exposure to conditioned medium and was still observable 10 min after exposure. Immunohistochemistry also demonstrated nuclear translocation of both Stat1 and Stat3 after stimulation of trophoblasts with medium from activated PBMC. These findings are compatible with the hypothesis that immunologic balance at the maternal-fetal interface is maintained by ongoing "cross-talk" between the fetus (and fetally-derived tissues) and the maternal immune system. Infection of the maternal vaginal tract may disrupt this delicate immunologic balance, initiating inflammatory events that ultimately result in preterm labor.

Neonatal-onset multisystem inflammatory disease responsive to interleukin-1beta inhibition

BACKGROUND

Neonatal-onset multisystem inflammatory disease is characterized by fever, urticarial rash, aseptic meningitis, deforming arthropathy, hearing loss, and mental retardation. Many patients have mutations in the cold-induced autoinflammatory syndrome 1 (CIAS1) gene, encoding cryopyrin, a protein that regulates inflammation.

METHODS

We selected 18 patients with neonatal-onset multisystem inflammatory disease (12 with identifiable CIAS1 mutations) to receive anakinra, an interleukin-1-receptor antagonist (1 to 2 mg per kilogram of body weight per day subcutaneously). In 11 patients, anakinra was withdrawn at three months until a flare occurred. The primary end points included changes in scores in a daily diary of symptoms, serum levels of amyloid A and C-reactive protein, and the erythrocyte sedimentation rate from baseline to month 3 and from month 3 until a disease flare.

RESULTS

All 18 patients had a rapid response to anakinra, with disappearance of rash. Diary scores improved (P<0.001) and serum amyloid A (from a median of 174 mg to 8 mg per liter), C-reactive protein (from a median of 5.29 mg to 0.34 mg per deciliter), and the erythrocyte sedimentation rate decreased at month 3 (all P<0.001), and remained low at month 6. Magnetic resonance imaging showed improvement in cochlear and leptomeningeal lesions as compared with baseline. Withdrawal of anakinra uniformly resulted in relapse within days; retreatment led to rapid improvement. There were no drug-related serious adverse events.

CONCLUSIONS

Daily injections of anakinra markedly improved clinical and laboratory manifestations in patients with neonatal-onset multisystem inflammatory disease, with or without CIAS1 mutations. (ClinicalTrials.gov number, NCT00069329 [ClinicalTrials.gov].).

hCG Secretion in Human Choriocarcinoma JAR Cells is MAPK but not Stat3 Dependent: Contributions of TNFα and IL-1β to Inflammation-induced hCG Secretion

Inflammatory mediators play critical physiologic roles throughout the course of normal pregnancy. At the same time, uncontrolled inflammation appears to have an adverse affect on pregnancy outcome. Thus, a crucial task of reproductive immunology is to define the mechanisms through which inflammation is controlled at the maternal-fetal interface. We examined the signaling pathways activated in the human choriocarcinoma cell line, JAR, in response to an in vitro model of an inflammatory challenge. We incubated JAR cells with medium from peripheral blood mononuclear cells (PBMC) that had been activated with either LPS or PHA. Conditioned medium from each experimental model induced MAP kinase and Stat3 phosphorylation as well as human chorionic gonadotropin (hCG) secretion from JAR cells. hCG secretion could be blocked by pharmacologic inhibition of MAP kinase but not by inhibition of Stat3 using an siRNA approach. The MAPK activators IL-1beta and TNFalpha both induced hCG secretion from JAR cells, but not the Stat3 activators IFN-gamma and IL-6. Furthermore, hCG secretion induced by conditioned media could be blocked by IL-1 receptor antagonist. We conclude that inflammation at the maternal-fetal interface may involve complex webs of regulatory and counter-regulatory mechanisms that involve multiple cytokines and at least two major, independent cell-signaling systems.

Lactic Acidosis in Gabonese Children with Severe Malaria Is Unrelated to Dehydration

BACKGROUND

Hyperlactatemia is an important and common complication of severe malaria. We investigated changes in fluid compartment volumes in patients with severe malaria and control patients with the use of bioimpedence analysis.

METHODS

We estimated extracellular water and total body water volumes in a total of 180 children: 56 with severe malaria, 94 with moderate malaria, 24 with respiratory tract infection, and 6 with severe diarrhea.

RESULTS

There was a mean (+/-SD) decrease in total body water volume of 17+/-24 mL/kg (or 3% of total body water volume) in patients with severe malaria. This compares with a mean (+/-SD) decrease in total body water volume of 33+/-28 mL/kg (or 6% of total body water volume) in patients with severe diarrhea. There was no increase in extracellular water volume in patients with severe malaria, suggesting no significant intravascular volume depletion in patients with severe malaria. There was no relationship between lactatemia and any changes in fluid compartment volumes.

CONCLUSIONS

The changes in fluid volumes that were observed are unlikely to be of physiological significance in the pathophysiology of severe malaria.

Learned helplessness in children and adolescents with juvenile rheumatic disease

OBJECTIVE

To examine a learned helplessness conceptualization of psychological sequela in children and adolescents with juvenile rheumatic diseases (JRD) via an experimental procedure utilizing behavior-outcome contingent and noncontingent feedback.

METHODS

Thirty-eight children and adolescents with JRD completed measures of transient affect, self-efficacy for functional ability, and causal attributions prior to and immediately following a computerized learned helplessness induction procedure.

RESULTS

Children across contingent and noncontingent feedback conditions experienced decreased positive affect with a slightly more pronounced decline in the noncontingent condition. Noncontingent feedback resulted in poorer internalization of success for problem solving, while contingent feedback resulted in greater internalization of success for problem solving. Additionally, posttreatment control self-efficacy was significantly greater for children in the contingent condition that initially endorsed higher levels of internal task attributions.

CONCLUSIONS

Children with JRD who experience behavior-outcome contingency in their environment may develop increased perceptions of control over functional ability. Furthermore, environmental noncontingency may result in poorer internalization of success, whereas contingent reinforcement may enhance cognitive appraisal mechanisms (i.e., causal attributions) associated with favorable disease outcome. Despite a modest decline in positive affect for children in the noncontingent condition, mood dysfunction is not entirely explicable within the context of noncontingent reinforcement.

Evidence for chronic, peripheral activation of neutrophils in polyarticular juvenile rheumatoid arthritis

Although strong epidemiologic evidence suggests an important role for adaptive immunity in the pathogenesis of polyarticular juvenile rheumatoid arthritis (JRA), there remain many aspects of the disease that suggest equally important contributions of the innate immune system. We used gene expression arrays and computer modeling to examine the function in neutrophils of 25 children with polyarticular JRA. Computer analysis identified 712 genes that were differentially expressed between patients and healthy controls. Computer-assisted analysis of the differentially expressed genes demonstrated functional connections linked to both interleukin (IL)-8- and interferon-gamma (IFN-gamma)-regulated processes. Of special note is that the gene expression fingerprint of children with active JRA remained essentially unchanged even after they had responded to therapy. This result differed markedly from our previously reported work, in which gene expression profiles in buffy coats of children with polyarticular JRA reverted to normal after disease control was achieved pharmacologically. These findings suggest that JRA neutrophils remain in an activated state even during disease quiescence. Computer modeling of array data further demonstrated disruption of gene regulatory networks in clusters of genes modulated by IFN-gamma and IL-8. These cytokines have previously been shown to independently regulate the frequency (IFN-gamma) and amplitude (IL-8) of the oscillations of key metabolites in neutrophils, including nicotinamide adenine dinucleotide (phosphate) (NAD(P)H) and superoxide ion. Using real-time, high-speed, single-cell photoimaging, we observed that 6/6 JRA patients displayed a characteristic defect in 12% to 23% of the neutrophils tested. Reagents known to induce only frequency fluctuations of NAD(P)H and superoxide ion induced both frequency and amplitude fluctuations in JRA neutrophils. This is a novel finding that was observed in children with both active (n = 4) and inactive (n = 2) JRA. A subpopulation of polyarticular JRA neutrophils are in a chronic, activated state, a state that persists when the disease is well controlled pharmacologically. Furthermore, polyarticular JRA neutrophils exhibit an intrinsic defect in the regulation of metabolic oscillations and superoxide ion production. Our data are consistent with the hypothesis that neutrophils play an essential role in the pathogenesis of polyarticular JRA.

Gene expression profiling in pediatric rheumatic disease: what have we learned? what can we learn?

PURPOSE OF THIS REVIEW

Gene expression profiling is emerging as a promising methodology in pediatric rheumatology research. There is considerable interest in using this technology as the basis for diagnostic assays. This review will summarize the new knowledge.

RECENT FINDINGS

Most gene expression studies of children have been exploratory in nature. However, preliminary gene expression studies in juvenile dermatomyositis, systemic lupus erythematosus, and chronic forms of arthritis demonstrate both the promise and limits of this technology. It seems likely that gene expression profiling will significantly enhance our understanding of the immunopathology of childhood-onset rheumatic diseases; however, considerable impediments must be overcome before these assays move into the clinical arena.

SUMMARY

Gene expression profiling carries considerable potential to provide novel insights into the rheumatic diseases of childhood. Future developments will determine whether these technologies provide new clinical diagnostic or prognostic tools.

Activated peripheral blood mononuclear cells induce p44/42 mitogen-activated protein kinase phosphorylation in trophoblast-like JAR cells

Mammalian pregnancy bears many similarities to transplantation, since the fetus is semi-allogenic to mother. Thus, mammals have developed numerous mechanisms to protect the developing fetus from maternal immunologic recognition and attack. We have previously shown that human choriocarcinoma JAR cells, which resemble first trimester trophoblasts, regulate several important mRNAs in activated peripheral blood mononuclear cells (PBMC). We now provide further evidence that communication between maternal and fetal tissues is bi-directional, and that activation of PBMC leads to activation of specific signaling pathways in JAR cells. Activated PBMC were co-cultured with JAR cells for specific time intervals, after which JAR cells were lysed and subjected to western blotting for activated forms of the JNK, Erk 1-2, and p38 mitogen-activated protein kinases (MAPK). Phosphorylation of Erk 1-2, but not JNK or p38, was induced in co-cultures of PBMC and JAR cells. These results were also obtained when JAR cells were incubated with conditioned medium from activated, but not resting, PBMC. Results were confirmed using specific MAPK reporter constructs, using luciferase activity as a measure of Elk-1 phosphorylation. Erk 1-2 phosphorylation was not required for JAR cells to inhibit IL-2 production in activated PBMC. Addition of the specific MAPK inhibitor UO126 to JAR cells prior to the addition of activated PBMC to the cultures did not abolish the capacity of JAR cells to inhibit IL-2 mRNA expression in PBMC. We conclude that there is likely to be significant bi-directional signaling between leukocytes and trophoblasts at the maternal-fetal interface. We propose the existence of a delicate maternal-fetal immunologic homeostasis based on these experimental results.

Hypervariable genes--experimental error or hidden dynamics

In a homogeneous group of samples, not all genes of high variability stem from experimental errors in microarray experiments. These expression variations can be attributed to many factors including natural biological oscillations or metabolic processes. The behavior of these genes can tease out important clues about naturally occurring dynamic processes in the organism or experimental system under study. We developed a statistical procedure for the selection of genes with high variability denoted hypervariable (HV) genes. After the exclusion of low expressed genes and a stabilizing log-transformation, the majority of genes have comparable residual variability. Based on an F-test, HV genes are selected as having a statistically significant difference from the majority of variability stabilized genes measured by the 'reference group'. A novel F-test clustering technique, further noted as 'F-means clustering', groups HV genes with similar variability patterns, presumably from their participation in a common dynamic biological process. F-means clustering establishes, for the first time, groups of co-expressed HV genes and is illustrated with microarray data from patients with juvenile rheumatoid arthritis and healthy controls.

Cord blood and adult T cells show different responses to C1q-bearing immune complexes

We have previously shown that T cells can be activated through cell-surface C1q receptors, resulting in secretion of interferon-gamma (IFN-gamma) and tumor necrosis factor alpha (TNFalpha), further demonstrating the intimate linkage between innate and adaptive immunity. In this current report, we sought to determine whether: (1) T cell responses to C1q-bearing immune complexes are dependent on the maturational status of the T cells and (2) whether signaling through the C1q receptor on T cells modulates conventional activation mediated through the conventional T cell receptor (TCR)/CD3 signaling complex. We first examined the capacity of neonatal T cells to respond to C1q-bearing immune complexes using IFNgamma, IL-2, and MIF secretion as measures of activation (MIF was chosen because of its crucial role in coordinating innate and adaptive immunity). Neonatal T cells produced significantly less IFNgamma but not IL-2, when stimulated by C1q immune complexes compared with adult T cells. MIF levels did not exceed background levels in these experiments. Next, we examined the capacity of C1q-bearing immune complexes to regulate signaling through the conventional TCR/CD3 signaling complex. Pre-incubating adult T cells with C1q-bearing immune complexes significantly reduced IFNgamma secretion when those same cells were subsequently stimulated with anti-CD3 and anti-CD28 monoclonal antibodies. Pre-incubation of neonatal T-cells with C1q-bearing immune complexes had no effect on IFNgamma secretion, although IFNgamma secretion was lower than that found in adult T cells for each experimental condition. We speculate that reduced IFNgamma secretion after pre-incubation with C1q immune complexes may be due to IL-10 secretion, which was observed in C1q-stimulated adult (but not neonatal) T cells.

CONCLUSIONS

C1q-bearing immune complexes exert complex effects on mature T cells that include both pro- and anti-inflammatory responses. Immunologic maturation is required for these effects, as cord blood T cells are relatively hyporesponsive to C1q-bearing immune complexes compared with adult T cells.

Chronic arthritis in children and adolescents in two Indian health service user populations

Background

High prevalence rates for rheumatoid arthritis, spondyloarthopathies, and systemic lupus erythematosus have been described in American Indian and Alaskan Native adults. The impact of these diseases on American Indian children has not been investigated.

Methods

We used International Classification of Diseases-9 (ICD-9) codes to search two Indian Health Service (IHS) patient registration databases over the years 1998–2000, searching for individuals 19 years of age or younger with specific ICD-9-specified diagnoses. Crude estimates for disease prevalence were made based on the number of individuals identified with these diagnoses within the database.

Results

Rheumatoid arthritis (RA) / juvenile rheumatoid arthritis (JRA) was the most frequent diagnosis given. The prevalence rate for JRA in the Oklahoma City Area was estimated as 53 per 100,000 individuals at risk, while in the Billings Area, the estimated prevalence was nearly twice that, at 115 per 100,000. These rates are considerably higher than those reported in the most recent European studies.

Conclusion

Chronic arthritis in childhood represents an important, though unrecognized, chronic health challenge within the American Indian population living in the United States.

Clinical utility of antinuclear antibody tests in children

BACKGROUND

Antinuclear antibody (ANA) tests are frequently used to screen children for chronic inflammatory diseases such as systemic lupus erythematosus (SLE). However, the diagnostic utility of this test is limited because of the large number of healthy children who have low-titer positive tests. We sought to determine the clinical utility of ANA tests in screening children for rheumatic disease and to determine whether there are specific signs or symptoms that enhance the clinical utility of ANA tests in children.

METHODS

We undertook a retrospective analysis of 509 new patient referrals. Charts of patients referred because of results of ANA testing were selected for further analysis. Children with JRA, SLE, and other conditions were compared using demographic data, chief complaints at the time of presentation, and ANA titers.

RESULTS

One hundred ten patients were referred because of an ANA test interpreted as positive. Ten patients were subsequently diagnosed with SLE. In addition, we identified one patient with mixed connective tissue disease, and an additional child with idiopathic Raynaud's phenomenon. Eighteen children of the children referred for a positive ANA test had juvenile rheumatoid arthritis (JRA). Another 80 children with positive ANA tests were identified, the majority of whom (n = 39, 49%) had musculoskeletal pain syndromes. Neither the presence nor the titer of ANA served to distinguish children with JRA from children with other musculoskeletal conditions. Children with JRA were readily identified on the basis of the history and physical examination. Children with SLE were therefore compared with children with positive ANA tests who did not have JRA, designated the "comparison group." Non-urticarial rash was more common in children with SLE than in children without chronic inflammatory disease (p = 0.007). Children with SLE were also older (mean +/- sd = 14.2 +/- 2.5 years) than the comparison group (11.0 +/- 3.6 years; p = 0.001). ANA titer was also a significant discriminator between children with SLE and children without chronic inflammatory disease. The median ANA titer in children with SLE was 1: 1,080 compared with 1:160 for other children (p < 0.0001). ANA titers of >/=1,080 had a positive predictive value for SLE of 1.0 while titers of </=1: 360 had a negative predictive value for lupus of 0.84.

CONCLUSION

Age and ANA titer assist in discriminating children with SLE from children with other conditions. ANA tests are of no diagnostic utility in either making or excluding the diagnosis of JRA.

Gene expression arrays reveal a rapid return to normal homeostasis in immunologically-challenged trophoblast-like JAR cells

The immunologic adaptations of pregnancy have come under increasing scrutiny in the past 15 years. Existing experimental evidence clearly demonstrates that placental trophoblasts play an important role in regulating immunologic/inflammatory responses at the maternal-fetal interface. We used a well-developed gene expression array to examine in greater detail the physiologic response of trophoblast-like choriocarcinoma cells to a model immunologic 'challenge.' We co-cultured PHA-activated or resting peripheral blood mononuclear cells (PBMC) with the human choriocarcinoma cell line JAR for time periods ranging from 2 to 18 h. Messenger RNA expression in the JAR cells was then assessed using a 21,329-gene microarray and novel biostatistical analyses that we have previously published. Patterns of differential gene expression were assessed using a commercial pathway analysis software program. Differences in gene expression between JAR cells cultured with activated PBMC (experimental samples) and JAR cells cultured with resting PBMC (control samples) were seen only at the 2h time point. That is, multiple genes were transcribed in JAR cells in response to activated PBMC, but expression levels of the genes had all returned to baseline by 6h. Molecular modeling demonstrated that the differentially expressed genes were largely associated with cell growth and differentiation. This model was confirmed by noting a two-fold increase in CD10/neutral endopeptidase expression (a marker for cell differentiation) in JAR cells incubated with media from activated PBMC compared with JAR cells incubated with resting PBMC. These findings support the hypothesis that there is a delicate immunologic milieu at the maternal-fetal interface that must be maintained. Immunologic/inflammatory challenge at the maternal-fetal interface is compensated by cellular mechanisms that work to reduce inflammation and rapidly restore immunologic balance.

Rheumatic disease in native american children: Opportunities and challenge

Rheumatic diseases are prevalent in Native American adults at rates five to seven times higher than those seen in the Caucasian population. Little, however, has been published concerning rheumatic diseases in Native American children. The authors' work in Oklahoma and with tribes on the northern Great Plains demonstrates high rates of childhood-onset rheumatic disease in this population. Familial disease is common, and large, multiplex kindreds showing strong founder effects are likely found within specific Native American tribes. However, a deeper understanding of the genetic and environmental triggers of rheumatic disease in Native Americans will require a respect and appreciation for the specific and unique cultural and social issues that impinge on research with Native Americans and other indigenous people.

Novel approaches to gene expression analysis of active polyarticular juvenile rheumatoid arthritis

Juvenile rheumatoid arthritis (JRA) has a complex, poorly characterized pathophysiology. Modeling of transcriptosome behavior in pathologic specimens using microarrays allows molecular dissection of complex autoimmune diseases. However, conventional analyses rely on identifying statistically significant differences in gene expression distributions between patients and controls. Since the principal aspects of disease pathophysiology vary significantly among patients, these analyses are biased. Genes with highly variable expression, those most likely to regulate and affect pathologic processes, are excluded from selection, as their distribution among healthy and affected individuals may overlap significantly. Here we describe a novel method for analyzing microarray data that assesses statistically significant changes in gene behavior at the population level. This method was applied to expression profiles of peripheral blood leukocytes from a group of children with polyarticular JRA and healthy control subjects. Results from this method are compared with those from a conventional analysis of differential gene expression and shown to identify discrete subsets of functionally related genes relevant to disease pathophysiology. These results reveal the complex action of the innate and adaptive immune responses in patients and specifically underscore the role of IFN-γ in disease pathophysiology. Discriminant function analysis of data from a cohort of patients treated with conventional therapy identified additional subsets of functionally related genes; the results may predict treatment outcomes. While data from only 9 patients and 12 healthy controls was used, this preliminary investigation of the inflammatory genomics of JRA illustrates the significant potential of utilizing complementary sets of bioinformatics tools to maximize the clinical relevance of microarray data from patients with autoimmune disease, even in small cohorts.

The influence of parental distress on child depressive symptoms in juvenile rheumatic diseases: the moderating effect of illness intrusiveness

OBJECTIVE

To examine the role of children's illness-related cognitive appraisals in the parent-child adjustment relationship in a sample of children and adolescents with juvenile rheumatic disease (JRD). Specifically, we tested the moderating effect of children's perceived illness-induced barriers (i.e., illness intrusiveness) in the parent distress-child depressive symptom relationship.

METHODS

Participants were 45 children and adolescents (ages 9-17) diagnosed with JRD. Children completed measures of depressive symptoms (Children's Depression Inventory), functional disability (Juvenile Arthritis and Functional Assessment Report), and illness intrusiveness (Illness Intrusiveness Scale-adapted for children); parents completed a brief measure of global distress (Brief Symptom Inventory). The pediatric rheumatologist provided functional disability ratings following a routine physical exam.

RESULTS

Both increased parental distress and child illness intrusiveness were associated with greater child depressive symptoms. Direct effects were qualified by a significant Parent Distress x Illness Intrusiveness interaction. The influence of general parental distress on child depressive symptoms was enhanced under conditions of increased child-reported illness intrusiveness.

CONCLUSIONS

Results support transactional conceptualizations of child adjustment to chronic illness. Findings also emphasize the need to examine the interaction of parent and child variables, particularly cognitive appraisals, in child adjustment. Results and treatment implications for children with JRD are discussed in terms of reinforcement theories of depression.

T cell activation by soluble C1q-bearing immune complexes: implications for the pathogenesis of rheumatoid arthritis

Both innate and adaptive immune systems are thought to participate in the pathogenesis of rheumatoid arthritis in adults and children. The experiments reported here were undertaken to examine how immune complexes, potent stimulators of inflammation, may regulate cells of the adaptive immune system. Human T cells were prepared from peripheral blood by negative selection and incubated with bovine serum albumin (BSA)-anti-BSA immune complexes that were formed in the presence or absence of human C1q. C1q-bearing immune complexes, but not unopsonized complexes, elicited both TNF-alpha and IFN-gamma secretion from human T cells. Secretion of both cytokines was time- and dose-dependent. Cross-linking C1q on the cell surface of T cells produced the same results. Cytokine secretion was not inhibited by blocking the C3b receptor (CR1, CD35) on T cells prior to incubation with immune complexes. Reverse transcriptase polymerase chain reaction (RT-PCR) of immune complex-stimulated cells revealed accumulation of both TNF-alpha and IFN-gamma mRNA within 2 h post-stimulation. IL-2 was not detected in cell culture supernatants, but IL-2 receptor alpha chain (CD25) was detected in low density on a small proportion of T cells activated by C1q-bearing immune complexes. Secretion of both cytokines was inhibited partially, but not completely, by IL-10. These experiments show that immune complexes, potent inflammatory mediators, may activate T cells through a novel mechanism. These findings have implications for chronic inflammatory diseases in humans.

Identifying children with chronic arthritis based on chief complaints: absence of predictive value for musculoskeletal pain as an indicator of rheumatic disease in children

OBJECTIVE

To examine complaints for which children were referred to a pediatric rheumatology service and to determine whether there are specific complaints that are more likely to indicate the presence of chronic arthritis or chronic, systemic inflammatory disease.

METHODS

A retrospective chart review of 414 children referred to the pediatric rheumatology service at the Children's Hospital of Oklahoma from April 1998 to July 2001.

RESULTS

Musculoskeletal pain was the most common complaint for which children were referred (n = 226). Of these, 111 had musculoskeletal pain as an isolated complaint. One of these children had a chronic inflammatory disease. Another 115 children had pain as 1 of several reasons for seeking a rheumatology consultation, including positive results on laboratory tests (antinuclear antibody, erythrocyte sedimentation rate, and rheumatoid factor). Nineteen of these children had a chronic inflammatory disease, including 12 with juvenile rheumatoid arthritis (JRA). Thus, musculoskeletal pain as a presenting complaint had a strong negative predictive value for the presence of either JRA (0.95) or any other chronic inflammatory disease that might be characterized by arthritis. Children who were referred, in part, because of positive antinuclear antibody and/or rheumatoid factor tests were no more likely to have a chronic inflammatory disease than children who did not include such results as a reason for referral. Joint swelling, in contrast, was the most likely complaint to be associated with a diagnosis of JRA.

CONCLUSIONS

Musculoskeletal pain was the most common reason for referral to our pediatric rheumatology clinic. However, isolated musculoskeletal pain, in the absence of other signs or symptoms, is almost never a presenting complaint of children with chronic forms of arthritis. Children with arthritis more commonly present with complaints of joint swelling and/or gait disturbance. Neither ANA nor rheumatoid factor evaluations were useful in evaluating children with musculoskeletal complaints.

C1q-bearing immune complexes induce IL-8 secretion in human umbilical vein endothelial cells (HUVEC) through protein tyrosine kinase- and mitogen-activated protein kinase-dependent mechanisms: evidence that the 126 kD phagocytic C1q receptor mediates immune complex activation of HUVEC

Endothelial cells play a pivotal role in the initiation and perpetuation of inflammation. C1q, the first component of the classical pathway of complement, is a potent stimulus leading to endothelial cell activation and cytokine production. The specific cellular mechanisms through which endothelial cells are stimulated by C1q are not known. We stimulated human umbilical vein endothelial cells (HUVEC) with either monomeric C1q or C1q-bearing immune complexes (C1q-IC) in the presence or absence of inhibitors of protein tyrosine kinases (PTK) or mitogen-activated protein kinases (MAPK). C1q-IC, but not monomeric C1q, induced IL-8 production in dose- and time-dependent fashion. R3, a cross-linking monoclonal IgM antibody against the 126 kD phagocytic C1q receptor (C1qR), also stimulated IL-8 production. IL-8 mRNA accumulation was detected by Northern blot analysis within 2 h of stimulation by the immune complexes and was enhanced by the addition of cycloheximide. Secretion of IL-8 by C1q-IC stimulated HUVEC was completely blocked by the PTK inhibitor, genistein or the MAPK inhibitor, UO126. These experiments demonstrate that C1q-IC-induced production of IL-8 in HUVEC is dependent upon the activation of PTK and MAPK. These findings also support a role for the phagocytic C1qR as an important activator of HUVEC by immune complexes.

Subspecialty referrals for pauciarticular juvenile rheumatoid arthritis

OBJECTIVES

To examine referral patterns from primary care physicians for children with pauciarticular juvenile rheumatoid arthritis (JRA) and to determine whether children with pauciarticular JRA referred to pediatric rheumatologists differ in clinical presentation from children referred to other specialists.

DESIGN

A retrospective records review of 49 patients with pauciarticular jRA was performed. Records were reviewed to determine the specialty of the referring physician and whether the children referred had symptoms and signs compatible with a synovitis at the time primary care was sought.

SETTING

Inner-city tertiary pediatric rheumatology referral center.

PARTICIPANTS

Children with pauciarticular JRA.

MAIN OUTCOME MEASURES

Identification of referral patterns of primary care physicians. Associated morbidity owing to JRA was ascertained at the time of referral.

RESULTS

Most children with pauciarticular JRA (62%) were referred to orthopedic surgeons prior to referral for pediatric rheumatology care. No differences in clinical symptoms were seen between children referred to pediatric rheumatologists and those referred to orthopedic surgeons. Children referred initially to orthopedic surgeons were younger than those referred to pediatric rheumatologists.

CONCLUSION

A notable number of children with pauciarticular JRA are referred to orthopedic surgeons prior to the establishment of that diagnosis, even when such children present with unequivocal signs of synovitis. This may be owing to the misconception that arthritis is rare in preschool-aged children or to the difficulty of ascertaining the presence of synovitis in younger children.

Immune complex size and complement regulate cytokine production by peripheral blood mononuclear cells

We have previously shown that immune complexes isolated from children with juvenile rheumatoid arthritis are heterogeneous in their size, composition, and proinflammatory capacities. The experiments described here were undertaken to clarify further the roles of size and composition in determining the proinflammatory effects of immune complexes. We incubated peripheral blood mononuclear cells (PBMCs) with different soluble immune complex preparations: opsonized complexes, which were formed in the presence of serum, unopsonized complexes, which were formed in the absence of serum, and immune precipitates solubilized by complement after their formation. ELISA assays showed that immune complexes formed in the presence of complement were less efficient than unopsonized complexes in inducing IL-1beta and IL-8 secretion from leukocytes. Solubilized immune precipitates showed intermediate capacity to stimulate the release of both cytokines. Complexes formed in heat-inactivated serum were as efficient as unopsonized complexes in eliciting cytokine secretion from the cells. The capacity of complement to regulate cytokine secretion from leukocytes was related, at least in part, to immune complex size. Sucrose density gradients showed unopsonized complexes and solubilized immune precipitates were larger than opsonized immune complexes. In contrast, fluid-phase binding of C4 to immune complexes, which did not appreciably change immune complex size, substantially increased IL-1beta secretion from PBMC.

Complement deposition on immune complexes reduces the frequencies of metabolic, proteolytic, and superoxide oscillations of migrating neutrophils

Neutrophils exhibit intrinsic sinusoidal metabolite concentration oscillations of 3 min in resting cells and an additional approximately 10- or 20-s oscillation in migrating/adhering cells. To better understand immune complex (IC)-mediated leukocyte activation, we have studied neutrophil metabolic oscillations in the presence of ICs either with or without fixed complement. Using a microscope photometer we quantitated NAD(P)H autofluorescence oscillations. Cells exposed to ICs exhibited metabolic oscillation periods of approximately 12 s in the absence of complement and approximately 22 s in the presence of complement opsonization. To determine if the effects could be associated with C3 deposition, we used ICs opsonized with only C3 or only C1 and C4. Untreated ICs, heat-inactivated complement-treated ICs, and C1,C4-treated ICs trigger rapid metabolic oscillations, as do fMLP and yeast; in contrast, ICs treated with full complement or C3 alone did not affect NAD(P)H oscillations in comparison to controls. The induction of higher frequency (approximately 10 s) NAD(P)H oscillations by ICs could be blocked by addition of anti-FcgammaRII, but not FcgammaRIII mAb fragments, suggesting the participation of FcgammaRII in cellular metabolic responses to ICs. Parallel changes in the frequencies of oxidant release and pericellular proteolysis were found for all of these stimuli. Thus, immune complex composition affects both intracellular metabolic signals and extracellular functional oscillations. We suggest that complement attenuates the phlogistic potential of ICs by reducing the frequency of cytoplasmic NAD(P)H oscillations.

Pathogenesis and mechanisms of inflammation in the childhood rheumatic diseases

The presence of CD4+ cells in the synovium of children with juvenile rheumatoid arthritis has led to the generally accepted hypothesis that aberrant activation or regulation of acquired immunity is central to the pathogenesis of this family of diseases; however, this hypothesis remains unproven, and, indeed, a specific role for T cells in the process of chronic synovitis in rheumatoid disease has yet to be identified for either adults or children. In contrast, processes associated with innate immunity are undeniably involved in the pathophysiology of chronic synovitis in both rheumatoid arthritis and juvenile rheumatoid arthritis. The presence of neutrophils in the synovial fluid, complement activation, and immune complex accumulation in the synovial fluid and serum all indicate an active inflammatory process. It is reasonable to hypothesize, therefore, that there are important clues to the cause of juvenile rheumatoid arthritis to be gleaned from a more careful study of inflammation or innate immunity. This review will focus on the roles of complement, immune complexes, and the vascular endothelium in the pathogenesis of juvenile rheumatoid arthritis. In so doing, it will reexamine the dogma of the central role of the T cell in juvenile rheumatoid arthritis disease pathogenesis and offer new paradigms with which to understand this and other rheumatic diseases of childhood.

Human choriocarcinoma JAR cells constitutively express pro-interleukin-1beta that can be released with Fc(gamma) receptor engagement

Some authors have suggested that fetally derived syncytiotrophoblasts, which form the barrier between mother and the fetus, are an integral part of a complex macrophage-cytokine network involving maternal leukocytes, decidual cells, placental tissues, and even the fetus itself. We report here that syncytiotrophoblast-like JAR cells, a human choriocarcinoma cell line, share another feature common to cells of the monocyte-macrophage lineage, the ability to secrete IL-1beta when stimulated through their Fc(gamma) receptors. We incubated JAR cells with physiologically relevant concentrations of model BSA-rabbit IgG-anti-BSA immune complexes or monomeric rabbit IgG for periods of up to 72 h. Both monomeric IgG and immune complexes induced IL-1beta from JAR cells, although levels produced by immune complexes were approximately twice those induced by monomeric IgG. IL-1beta secretion was not inhibited by cycloheximide, and Western blots of JAR cell lysates using pro-IL-1beta MAb revealed constitutive expression of a 31-kD protein, whose levels declined within 2 h of stimulation by either IgG or immune complexes, but returned to baseline within 18 h.

Constitutive expression c-fos, c-jun, and NF kappa B mRNA is in nucleated fetal blood cells and up-regulation of c-fos and c-jun with anti-CD3 stimulation

Fetal and neonatal lymphocytes are relatively resistant to activation and cytokine production when stimulated either via their T-cell antigen receptors or lectins. The molecular mechanism(s) responsible for this phenomenon have not been clearly elucidated. We have hypothesized that such defects in fetal/neonatal T-cell activation may be due to lack of expression of the transcriptional regulatory elements required for T-cell activation. We used reverse transcriptase-polymerase chain reaction to examine both fetal and term neonatal cord bloods for mRNA expression of three transcription factors implicated in T-cell activation: c-jun, c-fos, and NF kappa B (p50 subunit). We demonstrate that mRNAs for all three of these regulatory factors are expressed in fetal blood cells by the 27th week of gestation and in term cord bloods. Activation of term infant cord blood mononuclear cells with anti-CD3 monoclonal antibodies resulted in up-regulation of both c-jun and c-fos mRNAs within 15 min of stimulation. However, secretion of IL-2 by anti-CD3-stimulated cord blood mononuclear cells was still blunted compared with control cells from adults. We conclude that fetal nucleated blood cells constitutively express important genes for cytokine regulation and are able to increase intracellular accumulation of the mRNAs for these factors in response to anti-CD3 stimulation. Thus, qualitative differences in the capacity to regulate these factors could not be shown in fetal blood cells. Quantitative experiments comparing binding of these transcription factors to the IL-2 promoter are currently under investigation.

In vitro induction of proinflammatory cytokine secretion by juvenile rheumatoid arthritis synovial fluid immune complexes

OBJECTIVE

To characterize juvenile rheumatoid arthritis synovial fluid (SF) immune complexes and to examine their interaction with leukocytes.

METHODS

SF immunoglobulin-containing fractions were prepared by sequential chromatography on protein A and Sephacryl 300. Fractions were subdivided according to molecular weight, characterized for immunoglobulin and complement content, and incubated with either promonocytic U937 cells or normal human peripheral blood mononuclear cells (PBMC).

RESULTS

High molecular weight SF immunoglobulin-containing fractions stimulated the release of interleukin-1beta (IL-1beta) from U937 cells. These same complexes stimulated tumor necrosis factor alpha (TNFalpha), IL-1beta, IL-6, IL-8, and granulocyte-macrophage colony-stimulating factor (GM-CSF) from PBMC. Lower molecular weight material was less efficient in inducing any of the cytokines. TNFalpha and IL-1beta were the earliest of the messenger RNAs examined to be induced by the high molecular weight complexes. However, the secretion of IL-6, IL-8, and GM-CSF stimulated by the complexes was not completely dependent upon the secretion of IL-1beta. Addition of IL-1 receptor antagonist to the cell cultures reduced GM-CSF and IL-6 production by 40% and IL-8 production by 25% in PBMC.

CONCLUSION

SF immunoglobulin fractions contain immune complexes that vary in size, composition, and phlogistic potential. High molecular weight complexes are capable of inducing a spectrum of proinflammatory cytokines, all of which have been implicated in the pathogenesis of rheumatic disease.

Juvenile rheumatoid arthritis in African Americans

OBJECTIVE

To examine racial differences in disease expression in African American and Caucasian children with pauciarticular and polyarticular juvenile rheumatoid arthritis (JRA).

METHODS

A retrospective chart review was conducted of 35 African American and 137 Caucasian children with pauciarticular and polyarticular JRA.

RESULTS

African American children were significantly older than Caucasian children at the time of presentation. This was true both for the group as a whole and for each of the disease onset subtypes. African American children were less likely to have positive antinuclear antibody tests than Caucasian children. This finding paralleled a low incidence of uveitis in African American children. African American children were also more likely to have IgM rheumatoid factors (detected by latex agglutination) than Caucasian children. This was true even for African American children with pauciarticular JRA.

CONCLUSION

There are significant phenotypic differences between African American and Caucasian children with JRA.

Regulation of cytokine mRNA expression in activated lymphocytes by human choriocarcinoma JAR cells

Because the fetus is semiallogenic to the mother, considerable modulation of the maternal immune response must occur in order for pregnancy to be successfully carried to term. Some authors have hypothesized that the immunomodulation of pregnancy includes an adjustment of cytokine responses away from the Th1 paradigm and toward the Th2 pattern. In vivo data from murine pregnancy support this hypothesis. However, in humans, the Th1/Th2 model appears to be more complex than that in mice, and cytokine expression of mRNA in human decidual tissue does not reflect a clear-cut Th2 bias. The experiments described here were undertaken to determine whether and how trophoblastic cells modulate cytokine expression in activated lymphocytes, and whether there is a trend toward the use of the Th2 pattern in an experimental model of the maternal-fetal interface. We used reverse transcriptase polymerase chain reaction (rtPCR) to detect cytokine mRNA expression in human peripheral blood mononuclear cells cocultivated with human choriocarcinoma JAR cells. We found that although IL-2 (a paradigmatic Th1 cytokine) was significantly down-regulated by JAR cells at the mRNA level, similar decreases were also seen in IL-10, which participates in the Th2 paradigm. We were unable to detect changes in either interferon-gamma (IFN-gamma, a Th1 cytokine) or IL-4 (a Th2 cytokine) mRNA's or in IL-2R expression by fluorescence-activated cell sorting. These studies indicate that human choriocarcinoma JAR cells are capable of modifying cytokines in activated lymphocytes other than those involved in the Th1 paradigm. While it may be useful to view human responses against the background of these patterns established from murine systems, it is reasonable to conclude that human pregnancy may not involve regulation of Th1 immune responses exclusively.

Expression of complement regulatory proteins on fetal blood cells in utero

Since the fetus is semiallogenic to the mother, mechanisms have evolved to protect fetal tissue from the maternal immune response. Among these mechanisms is the expression of cell-surface complement regulatory proteins at the maternal-fetal interface. However, beginning in the third trimester, fetal blood cells are exposed to actively-transported IgG antibody. Thus, we speculated that fetal blood cells would require expression of one or more complement regulators by the early third trimester. Using flow cytometry and Western blots, we have demonstrated the presence of three important complement regulatory proteins in the circulating blood cells of human fetuses. These findings are consistent with the putative biological role of the cell-surface complement regulatory proteins.

Diminished expression of cell-surface complement regulatory proteins in HIV-infected children and with HIV infection of peripheral blood mononuclear cells in vitro

Experimental data have established that HIV-infected lymphocytes activate the complement system. However, because mammalian lymphocytes possess a series of cell-surface complement regulators that inhibit amplification on autologous cells, complement-mediated destruction of host cells is usually inhibited. These studies were performed to examine whether alterations in the cell-surface complement regulatory proteins decay-accelerating factor (DAF, CD55) and membrane cofactor protein (MCP, CD46) may occur during HIV infection in vitro or in vivo. The physiologic significance of these alterations were assessed by radiolabeled chromium release experiments. We show that MCP fluorescent intensity is significantly lessened in HIV-infected children and that DAF intensity is similarly lessened in infected children with advanced disease. These findings could be duplicated with HIV infection of peripheral blood mononuclear cells in vitro.

Composition and biological behaviour of immune complexes isolated from synovial fluid of patients with juvenile rheumatoid arthritis (JRA)

Data published from in vitro studies have shown that IgM-rheumatoid factor (RF)-bearing immune complexes possess several biological features that may contribute to their pathogenicity. However, no studies have demonstrated that such complexes exist at sites of inflammation in children with rheumatoid disease. We used two methods of sequential column chromatography to purify immune complexes from synovial fluids of children with JRA. We demonstrate that high molecular weight complexes contain IgM-RF, have not bound C4 in vivo, but activate the classical pathway in vitro. In contrast, complexes which have bound C3 in vivo do not contain IgM-RF and are weak complement activators in vitro.

Complement activation and immune complexes in early congenital HIV infection

Previous reports from our laboratory have shown that complement activation and the presence of circulating immune complexes are features of congenital human immunodeficiency virus (HIV) infection as they are in HIV-infected adults. The studies reported here were undertaken to (a) define whether complement activation is congenitally infected infants and children involves classic, alternative, or both pathways; (b) investigate the relationship between complement activation and circulating immune complexes; and (c) determine how early in congenital HIV infection complement activation and immune complexes can be found. We report that classic complement pathway activation and C1q-binding immune complexes can be found within the first 4 months of congenital HIV infection. However, the association between classic pathway activation and immune complexes before age 10 months was weak. These data raise interesting questions about complement-mediated immune complex processing in HIV-infected infants and young children.

Fetal cytokine expression in utero detected by reverse transcriptase polymerase chain reaction

Cytokine expression at the maternal-fetal interface is well documented. Some authors have postulated the existence of a bidirectional cytokine signaling mechanism that is critical to the maintenance of normal pregnancy. The role of the fetus (versus fetally derived placental tissues) in this process is unknown. Using reverse transcription polymerase chain reaction techniques, we studied paired maternal and fetal samples from 16 pregnancies (including two twin pregnancies) for the presence of tumor necrosis factor-alpha and IL-1 beta mRNA. We demonstrate that mRNA for both of these cytokines can be detected in both maternal and fetal blood as early as the 21st wk of gestation. These results support a potential role for the fetus in the bidirectional cytokine signaling of pregnancy.

Complement activation and immune complexes in children with polyarticular juvenile rheumatoid arthritis: a longitudinal study

OBJECTIVE

To determine whether levels of either circulating immune complexes (IC) or complement activation fragments change as disease activity changes in children with polyarticular juvenile rheumatoid arthritis (JRA).

METHODS

Twenty-six children with polyarticular JRA were examined over a time course of 4-21 months. Plasma complement activation fragments and IC were measured by commercially available enzyme linked immunoabsorbant assays.

RESULTS

Both complement activation fragments and IC levels were lower in individual children when their articular disease was inactive. Children with persistently active disease had no change in any of these measures.

CONCLUSION

Elevated levels of plasma IC and complement activation fragments are features of active polyarticular JRA. We believe our data support a role for the complement system in the pathophysiology of polyarticular JRA.

A comparison of immunoglobulin G-containing high-molecular-weight complexes isolated from children with juvenile rheumatoid arthritis and congenital human immunodeficiency virus infection

Circulating immune complexes have been described in both juvenile rheumatoid arthritis and in AIDS. We isolated high-molecular-weight complexes from plasma of children with juvenile rheumatoid arthritis and congenital human immunodeficiency virus infection by sequential gel filtration followed by affinity chromatography on protein A-Sepharose. We demonstrate that 1) mixed IgG-, IgM-, and IgA-bearing immune complexes can be found in both juvenile rheumatoid arthritis and congenital human immunodeficiency virus infection and 2) complexes isolated via affinity chromatography on protein A-Sepharose do not have detectable C4 but activate the classic complement pathway in vitro.