The cell-type-specific spatial organization of the anterior thalamic nuclei of the mouse brain

Understanding the cell-type composition and spatial organization of brain regions is crucial for interpreting brain computation and function. In the thalamus, the anterior thalamic nuclei (ATN) are involved in a wide variety of functions, yet the cell-type composition of the ATN remains unmapped at a single-cell and spatial resolution. Combining single-cell RNA sequencing, spatial transcriptomics, and multiplexed fluorescent in situ hybridization, we identify three discrete excitatory cell-type clusters that correspond to the known nuclei of the ATN and uncover marker genes, molecular pathways, and putative functions of these cell types. We further illustrate graded spatial variation along the dorsomedial-ventrolateral axis for all individual nuclei of the ATN and additionally demonstrate that the anteroventral nucleus exhibits spatially covarying protein products and long-range inputs. Collectively, our study reveals discrete and continuous cell-type organizational principles of the ATN, which will help to guide and interpret experiments on ATN computation and function.

Sharp cell-type-identity changes differentiate the retrosplenial cortex from the neocortex

The laminae of the neocortex are fundamental processing layers of the mammalian brain. Notably, such laminae are believed to be relatively stereotyped across short spatial scales such that shared laminae between nearby brain regions exhibit similar constituent cells. Here, we consider a potential exception to this rule by studying the retrosplenial cortex (RSC), a brain region known for sharp cytoarchitectonic differences across its granular-dysgranular border. Using a variety of transcriptomics techniques, we identify, spatially map, and interpret the excitatory cell-type landscape of the mouse RSC. In doing so, we uncover that RSC gene expression and cell types change sharply at the granular-dysgranular border. Additionally, supposedly homologous laminae between the RSC and the neocortex are effectively wholly distinct in their cell-type composition. In collection, the RSC exhibits a variety of intrinsic cell-type specializations and embodies an organizational principle wherein cell-type identities can vary sharply within and between brain regions.

Spatially patterned excitatory neuron subtypes and projections of the claustrum

The claustrum is a functionally and structurally complex brain region, whose very spatial extent remains debated. Histochemical-based approaches typically treat the claustrum as a relatively narrow anatomical region that primarily projects to the neocortex, whereas circuit-based approaches can suggest a broader claustrum region containing projections to the neocortex and other regions. Here, in the mouse, we took a bottom-up and cell-type-specific approach to complement and possibly unite these seemingly disparate conclusions. Using single-cell RNA-sequencing, we found that the claustrum comprises two excitatory neuron subtypes that are differentiable from the surrounding cortex. Multicolor retrograde tracing in conjunction with 12-channel multiplexed in situ hybridization revealed a core-shell spatial arrangement of these subtypes, as well as differential downstream targets. Thus, the claustrum comprises excitatory neuron subtypes with distinct molecular and projection properties, whose spatial patterns reflect the narrower and broader claustral extents debated in previous research. This subtype-specific heterogeneity likely shapes the functional complexity of the claustrum.

Elucidating memory in the brain via single-cell transcriptomics

Elucidating the neural mechanisms of memory in the brain is a central goal of neuroscience. Here, we discuss modern-day transcriptomics methodologies, and how they are well-poised to revolutionize our insight into memory mechanisms at unprecedented resolution and throughput. Focusing on the hippocampus and amygdala, two regions extensively examined in memory research, we show how single-cell transcriptomics technologies have been leveraged to understand the naïve state of these brain regions. Building upon this foundation, we show that these technologies can be applied to single-trial learning paradigms to comprehensively identify molecules and cells that participate in the encoding and retrieval of memory. Transcriptomics also provides an opportunity to understand the cell-type organization of the human hippocampus and amygdala, and due to conservation of these brain regions between humans and rodents, to infer behavioral and causal contributions in the human brain by leveraging rodent cell-type homologies and interventions. Ultimately, such transcriptomic technologies are poised to usher in a qualitatively novel understanding of memory in the brain.

Extensive and spatially variable within-cell-type heterogeneity across the basolateral amygdala

The basolateral amygdala complex (BLA), extensively connected with both local amygdalar nuclei as well as long-range circuits, is involved in a diverse array of functional roles. Understanding the mechanisms of such functional diversity will be greatly informed by understanding the cell-type-specific landscape of the BLA. Here, beginning with single-cell RNA sequencing, we identified both discrete and graded continuous gene-expression differences within the mouse BLA. Via in situ hybridization, we next mapped this discrete transcriptomic heterogeneity onto a sharp spatial border between the basal and lateral amygdala nuclei, and identified continuous spatial gene-expression gradients within each of these regions. These discrete and continuous spatial transformations of transcriptomic cell-type identity were recapitulated by local morphology as well as long-range connectivity. Thus, BLA excitatory neurons are a highly heterogenous collection of neurons that spatially covary in molecular, cellular, and circuit properties. This heterogeneity likely drives pronounced spatial variation in BLA computation and function.

Nutrient and plant secondary compound composition and iron-binding capacity in leaves and green stems of commonly used plant browse (Carolina willow; Salix caroliniana) fed to zoo-managed browsing herbivores

Plant secondary compounds are diverse structurally, and associated biological effects can vary depending on multiple factors including chemical structure and reaction conditions. Phenolic compounds such as tannins can chelate dietary iron, and supplementation of animal species sensitive to iron overload with tannins may prevent/treat iron overload disorder. We assessed the nutrient and phenolic composition and iron-binding capacity of Carolina willow (Salix caroliniana), a plant fed to zoo-managed browsing herbivores. Based on studies in other plant species and the chemical structures of phenolic compounds, we hypothesized that the concentration of condensed tannins in willow would be inversely related to the concentration of phenolic glycosides and directly related to iron-binding capacity. Our results indicated that willow nutrient composition varied by year, season, and plant part, which could be taken into consideration when formulating animal diets. We also found that the predominant plant secondary compounds were condensed tannins with minimal phenolic glycosides. Instead of binding to iron, the willow leaf extracts reduced iron from the ferric to ferrous form, which may have prooxidative effects and increase the bioavailability of iron depending on animal species, gastrointestinal conditions, and whole animal processes. We recommend identifying alternative compounds that effectively chelate iron in vitro and conducting chelation therapy trials in vivo to assess potential effects on iron balance and overall animal health.

Burden of copy number variation in common variable immunodeficiency

Common variable immunodeficiency (CVID) has been associated recently with a dramatic increase in total copy number variation burden, the cause of which is unclear. In order to explore further the origin and clinical relevance of this finding, we quantified the total genomic copy number variation (CNV) burden in affected patients and evaluated clinical details in relationship to total CNV burden. No correlation was found between total CNV burden and either patient age or time elapsed since symptom onset, and higher total burden did not correlate with incidence of malignancy or other subphenotypes. These findings suggest that the increased CNV burden is static and intrinsic to CVID as a disease.

Aberrant regulation of the integrin very late antigen-4 in systemic lupus erythematosus

Integrin very late antigen-4 (VLA4) is induced during inflammation and can regulate monocyte migration. It has been implicated in atherogenesis, a significant concern in systemic lupus erythematosus (SLE). The aim of this study was to define VLA4 expression in SLE monocytes. Flow cytometry, reverse transcription polymerase chain reaction, Western blotting, and immunohistochemistry staining with confocal microscopy were used to evaluate VLA4 expression in SLE patients and controls. We found elevated expression of VLA4 in SLE patients with significantly increased VLA4 staining intracellularly compared to control. Exposure of control monocytes to SLE sera or immune complexes led to increased intracellular expression, and immune complexes were capable of driving redistribution of surface VLA4 to the cytoplasm. Therefore, VLA4 was found to be subject to complex regulation with SLE sera driving both RNA expression and redistribution of protein. Stimulation of SLE monocytes with a VLA4 ligand induced significant TNFα expression, confirming a functional effect. This behavior may contribute to increased atherosclerosis and monocyte infiltrates in end organs.

Monocyte polarization: the relationship of genome-wide changes in H4 acetylation with polarization

The character of monocytes is both molded by and contributes to ongoing immune responses. We hypothesized that monocyte polarization could have durable qualities and these would be mediated partly by changes in the chromatin. We defined genome-wide expression and histone H4 acetylation (H4ac) changes after γ-interferon (IFN), α-IFN and interleukin-4 treatment. To identify genes with altered potential for expression, we stimulated polarized monocytes and identified genes up- or downregulated after polarization and stimulation but not either treatment alone. We also defined durability after an 18-h or 3-day washout. Genes uniquely regulated after the combination of polarization and stimulus were durably altered, with 51% of the effects being durable. This gene set was highly enriched for cytokine-induced alterations in H4ac, with P-values ranging from 10(-24) to 10(-37). Certain regulons defined by patterns of expression were also associated with altered H4ac, with P-values ranging from 10(-4) to 10(-29). Networking software revealed a high density of mitogen-activated protein (MAP) kinase nodes in these clusters. Therefore, some changes in monocyte gene expression were sustained over a 3-day period. These durably altered gene sets were enriched for changes in H4ac and were associated with potential MAP kinase effects.

Dyskeratosis congenita: a combined immunodeficiency with broad clinical spectrum--a single-center pediatric experience

BACKGROUND

Dyskeratosis Congenita (DKC) is a syndrome characterized by immunodeficiency, bone marrow failure, somatic abnormalities, and cancer predisposition resulting from defective telomere maintenance. The immunologic features of DKC remain under diagnosed and under treated despite the fact that immunodeficiency is a major cause of premature mortality in DKC.

METHODS

This study undertook a retrospective review of 7 DKC patients diagnosed at the Children's Hospital of Philadelphia. In parallel, we reviewed previously reported immunologic findings in DKC patients.

RESULTS

Immunologic abnormalities (lymphopenia, low B-cell numbers, hypogammaglobulinemia, and decreased T-cell function) were the most frequent laboratory findings at initial presentation, preceding the development of significant anemia or thrombocytopenia. Recurrent sinopulmonary or opportunistic infections were present in 6/7 patients. Infant-onset patients had more severe immunologic and somatic features (particularly severe enteropathy).

CONCLUSION

In DKC, development of immunologic abnormalities can precede bone marrow failure, highlighting the importance of proper immunodeficiency management to minimize morbidity and premature mortality in this disease.

Epigenetic regulation of tumor necrosis factor alpha

Tumor necrosis factor alpha (TNF-alpha) is a potent cytokine which regulates inflammation via the induction of adhesion molecules and chemokine expression. Its expression is known to be regulated in a complex manner with transcription, message turnover, message splicing, translation, and protein cleavage from the cell surface all being independently regulated. This study examined both cell lines and primary cells to understand the developmental regulation of epigenetic changes at the TNF-alpha locus. We demonstrate that epigenetic modifications of the TNF-alpha locus occur both developmentally and in response to acute stimulation and, importantly, that they actively regulate expression. DNA demethylates early in development, beginning with the hematopoietic stem cell. The TNF-alpha locus migrates from heterochromatin to euchromatin in a progressive fashion, reaching euchromatin slightly later in differentiation. Finally, histone modifications characteristic of a transcriptionally competent gene occur with myeloid differentiation and progress with differentiation. Additional histone modifications characteristic of active gene expression are acquired with stimulation. In each case, manipulation of these epigenetic variables altered the ability of the cell to express TNF-alpha. These studies demonstrate the importance of epigenetic regulation in the control of TNF-alpha expression. These findings may have relevance for inflammatory disorders in which TNF-alpha is overproduced.

Recurrent infections and immunological dysfunction in congenital disorder of glycosylation Ia (CDG Ia)

Congenital disorder of glycosylation Ia is the most common defect of glycosylation and is due to mutations in phosphomannomutase 2. This leads to aberrant N-linked oligosaccharides. The phenotype of CDG Ia reflects the essential nature of glycosylation and patients typically present with multiple organs affected, with hypotonia, developmental delay, inverted nipples and abnormal fat pads. Later features include retinitis pigmentosa, stroke, cerebellar atrophy and malabsorption. Approximately 20% of patients die in the first year of life and infection is the most common cause of death. Immunological function has not previously been investigated in these patients and the critical role of oligosaccharides on adhesion molecules suggested that haematopoietic cell migration and communication could be disrupted by mutations in phosphomannomutase 2. We characterized the clinical features, performed standard immunological evaluations, and performed specific analyses of neutrophil adhesion molecules on two patients to address this question. Patient neutrophils had diminished chemotaxis but expressed comparable levels of adhesion molecules and rolled on artificial endothelium equivalently to control neutrophils. The most significant feature of the patients' immunological function was poor vaccine responses. These two affected patients were begun on intravenous immunoglobulin with some improvement in their infections.

Abnormal apoptosis in chronic granulomatous disease and autoantibody production characteristic of lupus

OBJECTIVES

Patients with chronic granulomatous disease and carrier mothers of patients with chronic granulomatous disease are predisposed to developing various forms of lupus. This disorder is a neutrophil defect in intracellular killing. Abnormal apoptosis has been described. We hypothesized that abnormal apoptosis occurring in neutrophils of patients made them more immunogenic.

METHODS

Human patients with chronic granulomatous disease were examined for abnormalities of neutrophil apoptosis by flow cytometry. To model the effect of abnormal apoptosis, a murine model was used. Apoptotic cells from either wild type or mice with chronic granulomatous disease were injected into either wild type or chronic granulomatous disease mice and autoantibodies were determined by ELISA.

RESULTS

Our studies found that human and murine neutrophils carrying the gp91 form of chronic granulomatous disease had impaired exposure of phosphatidyl serine on the surface. Other markers of apoptosis were largely normal. Injection of apoptotic neutrophils from gp91 knockout mice into gp91 knockout mice led to the development of characteristic autoantibodies of lupus.

CONCLUSIONS

Humans with chronic granulomatous disease may be at an increased risk of developing lupus due to abnormal apoptosis and abnormal clearance of apoptotic cells.

Analysis of polymorphisms affecting immune complex handling in systemic lupus erythematosus

OBJECTIVES

Systemic lupus erythematosus (SLE) is a polygenic disorder of dysregulated inflammation. Numerous specific candidate genes have been identified and most relate to the handling of immune complexes or antigen presentation. This is consistent with the classic finding of immune complex deposition in affected end organs. We wished to examine combinatorial effects of polymorphic variants of genes involved in immune complex clearance in susceptibility to lupus.

METHODS

This study examined the occurrence of polymorphisms in genes which encode proteins known to be involved in immune complex handling and clearance. Each polymorphic variant of a complement protein (C2, mannose binding protein and C4), complement receptor (CR1) or Fc receptor (FcgammaRIIA and FcgammaRIIIA) gene is known to affect function adversely. One hundred and sixty SLE patients and 212 control subjects were genotyped using polymerase chain reaction methods.

RESULTS

We found an increasing association of SLE with increasing numbers of gene defects. Combinations of severe defects in FcgammaRIIA and FcgammaRIIIA were particularly deleterious for both African American and Caucasian patients, even though only one defective variant was individually statistically significantly associated with SLE.

CONCLUSIONS

The results of the study suggest that genes may interact in ways that either synergize or modify the effect of a single genetic effect and imply that association studies must be interpreted within the genetic background of the populations.

An osteopontin (SPP1) polymorphism is associated with systemic lupus erythematosus

Osteopontin (SPP1) is a soluble ligand with pleomorphic immunologic activities including activation of macrophage chemotaxis, promotion of Th1 responses, and activation of B1 B cells. It has been implicated in the development of murine lupus and is overexpressed in humans with systemic lupus erythematosus (SLE). We examined a polymorphism of osteopontin for an association with lupus in humans in an effort to determine whether there is any evidence that a genetic predisposition to altered osteopontin expression might explain the overexpression seen in human SLE patients. A silent polymorphism (707C>T, rs1126616) of osteopontin was significantly associated with SLE. Additional associations with renal disease and opportunisitic infections were suggested. This is the first phenotypic association with a polymorphic variant of osteopontin.

Immunologic features of chromosome 22q11.2 deletion syndrome (DiGeorge syndrome/velocardiofacial syndrome)

OBJECTIVES

To characterize immunologic function and clinical characteristics in patients with chromosome 22q11.2 deletion syndrome and determine whether there was significant change over time.

METHODS

This study characterized the laboratory and clinical features of the immunodeficiency in a cohort of 195 patients with chromosome 22q11.2 deletion syndrome and used cross-sectional and analysis of variance to compare the findings in different age groups with control patients. Changes over time were also characterized by a model effect method in a subset of patients who were studied serially.

RESULTS

Diminished T cell counts in the peripheral blood are common in patients with chromosome 22q11.2 deletion syndrome. The pattern of changes seen with aging in normal control patients was also seen in patients with chromosome 22q11.2 deletion syndrome, although the decline in T cells was blunted. Autoimmune disease was seen in most age groups, although the types of disorders varied according to age. Infections were also common in older patients, though they were seldom life threatening.

CONCLUSIONS

Slow declines in T cell populations are seen in chromosome 22q11.2 deletion syndrome. Clinical manifestations of immunodeficiency, such as recurrent infection and autoimmune disease, were common in this population but had little relationship to specific immunologic laboratory features.

DiGeorge syndrome/chromosome 22q11.2 deletion syndrome

DiGeorge syndrome is characterized by conotruncal cardiac defects, hypocalcemia, and a hypoplastic thymus. Many, but not all, patients have a heterozygous deletion of chromosome 22q11.2. In its most severe form, it represents a devastating syndrome with high mortality. Patients with severe immunodeficiency are candidates for a thymic transplant or a fully matched bone marrow transplant. Fortunately, the majority of patients with either DiGeorge syndrome or chromosome 22q11.2 deletion syndrome have a mild to moderate immunodeficiency. These patients may develop recurrent infections or autoimmune disease.

Interferon-gamma polymorphisms in systemic lupus erythematosus

Interferon-gamma is a cytokine which is believed to play a role in both the susceptibility and pathogenesis of lupus. To determine whether genetic variants might influence the development of this polygenic autoimmune disease, we analyzed the gene frequency of eight different alleles in controls and patients with SLE. Ninety-nine controls and 136 patients with systemic lupus erythematosus were genotyped for a CA repeat in the first intron of the interferon-gamma gene. There were no statistically significant differences in the allele frequencies between patients and controls suggesting that these polymorphic variants do not influence susceptibility. We then examined whether any of these alleles were associated with specific clinical manifestations. Allele 1 was associated with gastrointestinal lupus while allele 6 was associated with more severe lupus. Allele 2 appeared to be protective for arthritis. This suggests that genetic variation in interferon-gamma expression might influence the disease course.

Cytokine and chemokine dysregulation in hyper-IgE syndrome

Hyper-IgE syndrome is characterized by severe recurrent staphylococcal infections, eczema, bone abnormalities, and markedly elevated levels of immunoglobulin E (IgE). The genetic basis is not known and the central immunologic defect is largely undefined. Reduced neutrophil chemotaxis is often described, and variable T cell defects have been demonstrated in some patients. It has been hypothesized that hyper-IgE is associated with a Th1/Th2 imbalance. We wished to characterize cytokine and chemokine imbalances that might reflect the underlying disease process or reflect ongoing pathologic processes. Nine patients with hyper-IgE syndrome and six controls were studied. Radioimmunoassays, flow cytometry, and gene array analyses were performed to characterize cytokine and chemokine production. Hyper-IgE patients express more IL-12, while ENA-78, MCP-3, and eotaxin are markedly underexpressed. Underexpression of a set of chemokines could explain a number of features of hyper-IgE syndrome and may offer a new paradigm for the understanding of this disorder.

Gamma interferon and lipopolysaccharide interact at the level of transcription to induce tumor necrosis factor alpha expression

Lipopolysaccharide (LPS) is a very potent inducer of tumor necrosis factor alpha (TNF-alpha) expression from monocytes and macrophages. Another inflammatory cytokine, gamma interferon (IFN-gamma), can potentiate the effects of LPS, but the mechanism is not thoroughly understood. Previous reports emphasized the ability of IFN-gamma to upregulate CD14 expression (the receptor for LPS), and nearly all studies have utilized sequential stimulation with IFN-gamma followed by LPS to exploit this phenomenon. This study demonstrates that IFN-gamma can upregulate the effect of LPS at the level of transcription. Human monoblastic Mono-Mac-6 cells produced up to threefold-greater levels of TNF-alpha when simultaneously stimulated with LPS and IFN-gamma compared to treatment with LPS alone. RNase protection studies showed a similar increase in RNA beginning as early as within 30 min. The synthesis of TNF-alpha mRNA in IFN-gamma- and LPS-treated Mono-Mac-6 cells was also temporally prolonged even though the message turnover rate was identical to that seen in LPS stimulated cells. The modulatory effect of IFN-gamma may be mediated by Jak2.

Decreased natural killer (NK) cell function in chronic NK cell lymphocytosis associated with decreased surface expression of CD11b

Chronic natural killer cell lymphocytosis (CNKL) is characterized by greatly increased numbers of natural killer (NK) cells and patients with this disease may survive for long periods. This is in contrast to patients with leukemic proliferations of NK cells who can have a rapidly progressive clinical course. We identified a pediatric patient who was largely healthy who had CNKL and we sought to determine if the expanded CD16(+)CD3(-) population in this patient functions differently than classical NK cells. Cytotoxic activity against NK cell-sensitive K562 target cells was present, but lower than that in control donors when calculated as lytic units per CD16(+)CD3(-) cell. This cytolytic activity was inducible in patient samples by IL-2/IL-12 stimulation proportionately to that induced in samples from control donors. Intracellular perforin was also present and induced in patient CD16(+)CD3(-) cells similarly to controls. Other presumed NK cell activities, such as IL-2/IL-12 induced IFN-gamma expression and initiation of apoptosis evidenced by annexin V binding after CD16 crosslinking were present in patient samples. Patient CD16(+)CD3(-) cells, however, differed from classical NK cells, as the majority did not express CD56, CD57, CD8, or CD11b. Most convincingly, there was a 5 log decrease in CD11b expression in patient CD16(+)CD3(-) cells compared to control as determined by mean channel fluorescence. These observed differences may explain the relatively benign phenotype of this disorder.

Measurement of cytokine secretion, intracellular protein expression, and mRNA in resting and stimulated peripheral blood mononuclear cells

Quantitation of cytokine production is a valuable adjunct to standard immunologic assays in defining several pathologic processes. Nevertheless, there is little agreement about which tissues should be assayed, which type of assay should be performed, and which stimulation protocol should be used. As these types of assays enter the clinical arena, there is need for standardization. There is also a need to maximize the amount of information which may be derived from a single sample. We compared secreted interleukin 4 (IL-4), IL-2, IL-6, tumor necrosis factor alpha (TNF-alpha), and gamma interferon proteins as measured by enzyme-linked immunosorbent assay with intracellular cytokine production (IL-2 and gamma interferon) as detected by flow cytometry and quantitative competitive PCR for IL-2, IL-4, TNF-alpha, and gamma interferon mRNA and cDNA. Results from unstimulated cells and cells stimulated with phorbol myristate acetate, phytohemagglutinin, and phorbol myristate acetate plus phytohemagglutin were compared. All three methodologies detected significant stimulation of cytokine production. The combination of phytohemagglutinin and phorbol myristate acetate was overall the most-potent stimulus.

3' polymorphisms of ETS1 are associated with different clinical phenotypes in SLE

A microsatellite repeat polymorphism was identified in the 3' flanking region of the human ETS1 gene. Sequencing revealed two CA repeat segments in close proximity. Seven different alleles comprising various combinations of CA repeat units were identified in a healthy control population. Because ETS1 plays a role in lymphocyte development and function, apoptosis, and inflammation, we examined whether any of these polymorphisms were associated with a systemic inflammatory condition, systemic lupus erythematosus (SLE). Inheritance of this disease is polygenic and a recent genome-wide screen for SLE susceptibility loci revealed linkage with chromosome 11q14-23, the region in which the ETS1 gene lies. This region has also been identified as a general autoimmune susceptibility region. None of the seven distinct ETS1 alleles appeared statistically more frequently in SLE patients than controls, however, two alleles were associated with particular clinical manifestations. Allele 1 is associated with discoid lesions and allele 7 is associated with vasculitis. While this polymorphism does not directly affect the coding region of ETS1, it may be a marker for overexpression of a particular isoform or inheritance of another polymorphism which does affect function. These data suggest that ETS1 may be involved in the phenotypic expression of systemic lupus erythematosus.

Genetics of systemic lupus erythematosus. Clinical implications

Rheumatic diseases have long been recognized as having complex inheritance patterns. It has recently been estimated that over 100 genes may be implicated in the SLE disease process. Identification of these genes has led to a greater understanding of the etiopathogenesis of SLE and is beginning to lead to new types of interventions directed at correcting aberrant biological processes.

The role of bone marrow transplantation in pediatric rheumatic diseases

Recent advances in bone marrow transplantation have led to improvement in its safety and it is now being used for rheumatologic disorders resistant to standard medical management. I describe some of the theories underlying its use and review the current data supporting its use.

Rapid method for determining the rate of DNA synthesis and cellular proliferation

A new method has been developed for determination of DNA synthesis during cell proliferation. The method is based on the metabolism of [U-(13)C(6)]glucose to deoxyribose (DR) and then incorporation of [U-(13)C(5)]DR into newly synthesized DNA. Extracted cellular DNA is subjected to HCl hydrolysis (2 h at 100 degrees C), which converts DR into levulinic acid. The (13)C enrichment in DR is determined in the trimethylsilyl derivative of levulinate using gas chromatography-mass spectrometry. The method is rapid and sensitive. It can precisely determine (13)C enrichment below 1 at.% excess in as little as 4 ng DNA. We have used this method to determine the rate of cell proliferation in vitro and the level of DR in a given amount of DNA. The current approach has significant advantages over previously described methods and overcomes several difficulties related to the determination of DNA synthesis both in vivo and in vitro.

A TNFR2 3' flanking region polymorphism in systemic lupus erythematosus

The role of pro-inflammatory cytokines in systemic lupus erythematosus (SLE) remains somewhat controversial. Several studies have shown increased production of TNF alpha and IL-6 in patients with SLE. Increased production of IL-6, TNF alpha, and IL-1 soluble receptors have also been reported. This finding is provocative because the soluble receptors have the capacity to act as antagonists. Several other inflammatory disorders are also associated with increased production of soluble TNF alpha receptors suggesting that this may be a general compensatory mechanism designed to down-regulate inflammation. The recent identification of an SLE disease susceptibility locus near the TNFR2 locus (TNFR p75) suggested the hypothesis that genetically driven differences in soluble TNFR2 production could play a role in the genetic susceptibility to SLE. We therefore characterized the frequency of a genetic polymorphism in the 3' untranslated region of the TNFR2 gene in Caucasoid SLE patients and geographically matched controls. No difference in the gene frequency of the two base-pair polymorphism in SLE patients compared to controls was found, nor was there any association with any particular clinical phenotype.

Longitudinal analysis of lymphocyte function and numbers in the first year of life in chromosome 22q11.2 deletion syndrome (DiGeorge syndrome/velocardiofacial syndrome)

Chromosome 22q11.2 deletion syndrome is a common syndrome typically consisting of variable cardiac defects, hypoparathyroidism, developmental delay, and immunodeficiency. The hemizygous deletion has variable effects on the immune system even within the same kindred, and the extent of the immunodeficiency is difficult to predict. Some patients have shown improvement over time; however, this is the first prospective longitudinal study of the dynamic nature of the immunodeficiency. Nineteen patients were studied prospectively between 1994 and 1997. The results of the newborn immunologic studies in the chromosome 22q11.2 deletion group were significantly different from those of a group of newborns with cardiac disease due to other causes. Peripheral blood T-cell numbers were decreased in the chromosome 22q11.2 deletion group, although T-cell function was largely preserved. The group as a whole demonstrated few changes in the first year of life, but a subset of patients with markedly diminished T-cell numbers did demonstrate improvement. Therefore, improvement in peripheral blood T-cell counts is variable in chromosome 22q11.2 deletion syndrome. The patients with the lowest T-cell counts improved the most in the first year of life.

C4A deficiency due to a 2 bp insertion is increased in patients with systemic lupus erythematosus

OBJECTIVE

The association of C4A deficiency with systemic lupus erythematosus (SLE) is well documented. In Caucasian populations, the most common cause of C4A deficiency is a large gene deletion in linkage disequilibrium with a conserved MHC haplotype. Because of this linkage disequilibrium, it has been difficult to determine which of the genes constitutes the disease susceptibility allele. Evidence from non-caucasoid populations has supported a role for C4A deficiency in SLE. We investigated whether a specific genetic cause of C4A deficiency, not associated with A1, B8, DR3, is found with increased frequency in SLE compared to controls.

METHODS

Polymerase chain reaction was used to identify carriers of a 2 base pair (bp) insertion in exon 29. In total, 188 patients with SLE from the Johns Hopkins lupus cohort and 222 controls were genotyped.

RESULTS

The 2 bp insertion was found more frequently in patients with SLE compared to controls and was more common in Caucasian than in African American SLE patients. There were no clinical differences between patients that carried the mutation and those that did not.

CONCLUSION

The association of this C4A null allele with SLE supports a role for C4A deficiency independent of other MHC associations in the etiopathogenesis of SLE.

Loss of endothelial surface expression of E-selectin in a patient with recurrent infections

Neutrophil accumulation at sites of inflammation is mediated by specific groups of cell adhesion molecules including the beta2 (CD18) integrins on leukocytes and the selectins (P- and E-selectin on the endothelium and L-selectin on the leukocyte). This is supported by studies of patients with leukocyte adhesion deficiency syndromes whose leukocytes are genetically deficient in the expression of beta2 integrins or selectin carbohydrate ligands (eg, sialyl-Lewis(x)). However, inherited deficiency or dysfunction of endothelial cell adhesion molecules involved in leukocyte recruitment has not been previously described. In this report we describe a child with recurrent infections and clinical evidence of impaired pus formation reminiscent of a leukocyte adhesion deficiency syndrome, but whose neutrophils were functionally normal and expressed normal levels of CD18, L-selectin, and sialyl-Lewis(x). In contrast, immunohistochemical staining of inflamed tissue from the patient showed the absence of E-selectin from the endothelium, although E-selectin mRNA was present. However, E-selectin protein was expressed as significantly elevated levels of circulating soluble E-selectin were detected, the molecular size of which was consistent with a proteolytically cleaved form of E-selectin. Gene sequencing failed to show evidence of a secreted mutant variant. These data represent, to our knowledge, the first description of a potentially inherited dysfunction of an endothelial cell adhesion molecule involved in leukocyte recruitment and provide additional human evidence of the importance of endothelial selectins in the inflammatory response.

Frequency of the Fc gamma RIIIA-158F allele in African American patients with systemic lupus erythematosus

OBJECTIVE

Defects in genes involved in immune complex clearance constitute one of the most common gene defects identified in patients with systemic lupus erythematosus (SLE). Defects in early complement components, complement receptors, and Fc receptors have all been implicated in the susceptibility to SLE. Recently, the role of functionally relevant Fc receptor polymorphisms in the etiology of SLE has been investigated. Specifically, a polymorphism of FC gamma RIII, termed Fc gamma RIIIA-158F, has been found to be associated with SLE in 2 largely Caucasian populations and appeared to constitute a risk factor for nephritis. We investigated the association of the Fc gamma RIIIA-158F and Fc gamma RIIIA-131R polymorphisms with SLE in an African American study population.

METHODS

Nested polymerase chain reaction (PCR) and allele-specific PCR was used to genotype patients with SLE and controls.

RESULTS

There was no difference in Fc gamma RIIIA-158F or Fc gamma RIIA-131R gene frequencies in the SLE populations compared to controls. There was no significant association between Fc gamma RIIIA-158F or Fc gamma RIIA-131R and any specific clinical or laboratory variable.

CONCLUSION

In our African American study population, there did not appear to be any association of Fc gamma RIIA-158F or Fc gamma RIIA-131R with SLE.

Recent advances in our understanding of Wiskott-Aldrich syndrome

Wiskott-Aldrich syndrome initially was described in 1937 and then again in 1954 as an X-linked disorder associated with thrombocytopenia, eczema, and recurrent infections. It remained mysterious how different cell lineages could be affected in this syndrome and, more importantly, how the phenotypic features could be so protean. We now know that the features associated with Wiskott-Aldrich syndrome include dysfunction of nearly all effector arms of the immune system, as well as thrombocytopenia with platelet dysfunction. As a consequence of these abnormalities, children and adults with this syndrome have recurrent bleeding, recurrent and significant infections with common and opportunistic organisms, autoimmune disease, and lymphoreticular malignancies. In 1994, the gene that is defective in Wiskott-Aldrich syndrome was identified and found to be a gene with limited homology to any known gene families. In the past 4 years, much has been learned about the role of this protein in cellular function and T-cell responses specifically. This article reviews some recent clinical findings relevant to Wiskott-Aldrich syndrome, the proposed cellular role of this molecule, its biochemical interactions, and genotype-phenotype considerations.

Complement deficiency and autoimmunity

Complete deficiency of one of the early components (C1, C4, or C2) of the classical pathway of the complement cascade is one of the strongest genetic risk factors for systemic lupus erythematosus that has been recognized. The lupus that occurs in complement-deficient individuals typically presents in early childhood. The association of complement deficiency and lupus has been known for over two decades, yet the explanation remains somewhat elusive. Complement component deficiencies may be associated with other rheumatic or autoimmune disorders and both partial and acquired complement component deficiencies are also associated with an increased risk of autoimmune disease. This article reviews the current understanding of the relationship between complement component deficiencies and autoimmunity. Recent data from animal models and new types of genetic analyses are reviewed.

The Fc gammaRIIIA-158F allele is a risk factor for systemic lupus erythematosus

OBJECTIVE

To study whether the Fc gammaRIIIA-158V/F polymorphism, which affects IgG binding affinity, is a risk factor for systemic lupus erythematosus (SLE).

METHODS

We genotyped a group of 70 Caucasian SLE patients for all known Fc gammaR polymorphisms. Of this group, 45 patients (64%) had nephritis. In 35 patients, this diagnosis was confirmed by renal biopsy.

RESULTS

In the total group of 70 SLE patients, the frequency of the Fc gammaRIIIA-158F allele was 0.74, versus 0.57 in healthy controls (P = 0.003). The genotype distribution of the Fc gammaRIIIA-158V/F polymorphism was also significantly different from that of the control population (P = 0.004). The distribution of the other Fc gammaR polymorphisms--Fc gammaRIIA-131R/H, Fc gammaRIIIB-NA(1,2), and Fc gammaRIIIA-48L/R/H--was similar in SLE patients and controls.

CONCLUSION

In our group of SLE patients, only the distribution of the alleles of the Fc gammaRIIIA-158V/F polymorphism was significantly different from that in the control group. This might indicate that macrophage expression of the Fc gammaRIIIA-158F isoform is involved in the disturbed clearance of immune complexes in patients with SLE.

Defective natural killer cell function in patients with hemophagocytic lymphohistiocytosis and in first degree relatives

Hemophagocytic lymphohistiocytosis (HLH), also referred to as familial erythrophagocytic lymphohistiocytosis, is a rare disorder of infancy associated with proliferation of activated histiocytes and T cells, anemia, thrombocytopenia, and fevers. This disorder appears to be due to the uncontrolled activation of T cells producing IL-2, tumor necrosis factor-alpha, and interferon-gamma. Untreated, the disorder is universally fatal. Various deficits in immune function have been described during acute disease activity including impaired T cell function, impaired monocyte-mediated antibody-dependent cytotoxicity, impaired natural killer cell function, and impaired IL-1 production. We examined natural killer cell function in familial HLH patients to determine whether this finding was consistently associated with the disease. We also examined natural killer cell function in asymptomatic parents and siblings of patients. Impaired natural killer cell function was identified in all patients and in some family members, including obligate carrier parents. This implies that one potential genetic defect in HLH may result in depressed natural killer function, but that this may not be sufficient to reliably predict eventual progression to disease.

Adenosine deaminase deficiency and purine nucleoside phosphorylase deficiency in common variable immunodeficiency

The clinical presentations of adenosine deaminase deficiency and purine nucleoside phosphorylase deficiency are widely variable and include clinical and immunologic findings compatible with common variable immunodeficiency. The screening of 44 patients with common variable immunodeficiency failed to identify any individuals with deficiencies of these enzymes.

Increased prevalence of immunoglobulin A deficiency in patients with the chromosome 22q11.2 deletion syndrome (DiGeorge syndrome/velocardiofacial syndrome)

We wished to determine the prevalence of immunoglobulin A (IgA) deficiency in patients with the chromosome 22q11.2 deletion syndrome. A total of 32 patients with the chromosome 22q11.2 deletion were examined for IgA deficiency. We report a 13% (n = 4) prevalence of IgA deficiency in patients with this syndrome. The odds ratio of IgA deficiency in this population is 14.20 (P < 0.0001). This confirms the occurrence of significant humoral deficits in this predominantly cellular immunodeficiency.

Successful use of extracorporeal membrane oxygenation (ECMO) during BMT for SCID

An 8-month-old girl with SCID presented with severe bronchiolitis. She received an HLA-identical sibling BMT without conditioning or GVHD prophylaxis. She deteriorated despite mechanical ventilation but had normal cardiac, hepatic and renal function. ECMO was instituted on day +3 and subsequent improvement was seen concurrently with emergence of CD4+ cells on day +11. She was taken off ECMO on day +18 and suffered a left-sided stroke evidenced by a dense left hemiplegia. She was extubated on day +25 and weaned from supplemental oxygen on day +36 and at day +100 has recovered strength in her extremities. This is the first successful use of ECMO as a bridge to engraftment in a BMT patient.

Lack of correlation between impaired T cell production, immunodeficiency, and other phenotypic features in chromosome 22q11.2 deletion syndromes

Monosomic deletions of chromosome 22q11.2 are the leading cause of DiGeorge syndrome, velocardiofacial syndrome, and conotruncal anomaly face syndrome. DiGeorge syndrome was originally described as an immunodeficiency disorder secondary to impaired T cell production due to thymic aplasia or hypoplasia; however, the frequency of immunodeficiency in the other clinical syndromes associated with the chromosome 22q11.2 microdeletion has not been previously investigated. This study examines the frequency and severity of impaired T cell production and immunodeficiency in chromosome 22q11.2 deletion syndromes and the relationship of the immunodeficiency to specific phenotypic features. Sixty patients over 6 months of age with the characteristic chromosome 22q11.2 deletion underwent immunologic evaluations. Seventy-seven percent of patients with chromosome 22q11.2 deletions were found to have evidence of immunocompromise. The severity of the immunodeficiency did not correlate with any particular phenotypic feature, nor was it restricted to patients who were categorized as having DiGeorge syndrome. Therefore, impaired T cell production and impaired immunologic function are common in patients with deletions of chromosome 22q11.2. The presence or severity of the immunocompromise cannot be predicted based on other phenotypic features and each child should be individually assessed for immune function.

A promoter polymorphism of tumor necrosis factor alpha associated with systemic lupus erythematosus in African-Americans

OBJECTIVE

The polymorphic tumor necrosis factor alpha (TNFalpha) gene encodes a cytokine involved in inflammation, angiogenesis, and apoptosis. One polymorphic variant is associated with increased production of TNFalpha. This study examined the frequency of this polymorphic variant in African-American patients with systemic lupus erythematosus (SLE) compared with controls.

METHODS

We determined the gene frequency of the polymorphic variant of TNFalpha in an African-American SLE patient population and in a geographically matched African-American control population.

RESULTS

The gene frequency of the TNFalpha -308A polymorphism was higher in the African-American SLE population than in the control population. This relationship was independent of major histocompatibility complex DR alleles.

CONCLUSION

The TNFalpha -308A polymorphism is associated with an increased risk of SLE in African-Americans.

Association of toxic shock syndrome toxin-secreting and exfoliative toxin-secreting Staphylococcus aureus with Kawasaki syndrome complicated by coronary artery disease

Kawasaki syndrome (KS) has been reported to be associated with selective expansion of Vbeta2+ T cells and either staphylococcal toxic shock syndrome toxin-1 or streptococcal pyrogenic exotoxin C in uncomplicated cases. However, there have been no previous studies on the role of superantigens in KS associated with coronary artery disease, the major complication of this illness. The present study characterized bacteria isolated from three acute KS patients who developed coronary artery disease. Staphylococcus aureus secreting either TSST-1 (n = 3) or exfoliative toxin A (n = 1), both known to stimulate expansion of Vbeta2+ T cells, were isolated from all three patients. The percent Vbeta2+ T cells was determined in three patients with coronary artery disease. On presentation, one patient demonstrated reduction, whereas the other two showed expansion, of Vbeta2+ T cells. Repeat analyses of the latter two children showed their percent Vbeta2+ T cells to decrease toward normal. These observations suggest that coronary artery disease in KS may result from superantigenic stimulation of Vbeta2+ T cells. This is also the first demonstration of an association of staphylococcal exfoliative toxin with acute KS. The observation that three different bacterial toxins associated with KS are potent activators of Vbeta2+ T cells suggests an important role for this T cell subset in the pathogenesis of this autoimmune disease.

Defective antigen-induced lymphocyte proliferation in the X-linked hyper-IgM syndrome

We examined T-cell proliferation in five patients with X-linked hyper-IgM syndrome (XHIM), using a panel of antigens and lectins. All patients had impaired antigen-induced proliferation, whereas their lectin responses were normal. Thus, in addition to severely depressed antibody responses, patients with XHIM have a defect in antigen-specific T-cell proliferation, which may explain their susceptibility to pathogens such as Pneumocystis carinii.

Four conserved promoter motifs regulate transcription of the gene encoding human complement component C2

The early complement components of the classical activation pathway of the complement cascade include the components C1, C4, C2, and C3. These components act in concert to opsonize bacteria, clear immune complexes, and produce inflammatory mediators. They are not structurally homologous nor are they coordinately regulated. The expression of the early complement components is divergent in terms of cytokine responsiveness and tissue specificity. The only pattern of expression shared by the early complement components is inducibility by gamma-IFN and expression in cells of hepatic or monocytic lineage. Nevertheless, four novel conserved promoter motifs were identified in the 5' flanking region of multiple early complement component promoters. Mutation of these four motifs in the C2 promoter decreased transcription in hepatoma cells in transient transfection analyses, and a synthetic promoter consisting of just the four motifs supported transcription in hepatoma cells. Electrophoretic mobility shift assays demonstrate that three of the four conserved elements bind DNA-binding proteins in a tissue-specific manner. One DNA-binding protein is expressed ubiquitously, but the other three are restricted to cells of monocytic or hepatic lineage. Two of the DNA-binding proteins appear to be members of the zinc-finger family of transcription factors. Therefore, these four motifs appear to bind DNA-binding proteins that may function in the tissue-specific expression of C2. Conservation of these four motifs in multiple early complement component genes suggests that these may represent a conserved transcriptional strategy.

Four conserved promoter motifs regulate transcription of the gene encoding human complement component C2

The early complement components of the classical activation pathway of the complement cascade include the components C1, C4, C2, and C3. These components act in concert to opsonize bacteria, clear immune complexes, and produce inflammatory mediators. They are not structurally homologous nor are they coordinately regulated. The expression of the early complement components is divergent in terms of cytokine responsiveness and tissue specificity. The only pattern of expression shared by the early complement components is inducibility by gamma-IFN and expression in cells of hepatic or monocytic lineage. Nevertheless, four novel conserved promoter motifs were identified in the 5' flanking region of multiple early complement component promoters. Mutation of these four motifs in the C2 promoter decreased transcription in hepatoma cells in transient transfection analyses, and a synthetic promoter consisting of just the four motifs supported transcription in hepatoma cells. Electrophoretic mobility shift assays demonstrate that three of the four conserved elements bind DNA-binding proteins in a tissue-specific manner. One DNA-binding protein is expressed ubiquitously, but the other three are restricted to cells of monocytic or hepatic lineage. Two of the DNA-binding proteins appear to be members of the zinc-finger family of transcription factors. Therefore, these four motifs appear to bind DNA-binding proteins that may function in the tissue-specific expression of C2. Conservation of these four motifs in multiple early complement component genes suggests that these may represent a conserved transcriptional strategy.

Juvenile rheumatoid arthritis-like polyarthritis in chromosome 22q11.2 deletion syndrome (DiGeorge anomalad/velocardiofacial syndrome/conotruncal anomaly face syndrome)

OBJECTIVE

To investigate the association of polyarthritis and chromosome 22q11.2 deletions.

METHODS

Eighty patients with chromosome 22q11.2 deletion syndrome followed up at The Children's Hospital of Philadelphia were examined for evidence of arthropathy or arthritis. Patients with chromosome 22q11.2 deletion syndrome and polyarthritis underwent laboratory evaluations of immunologic function to determine the relationship of their immunodeficiency to the polyarthritis.

RESULTS

The prevalence of polyarthritis in patients with chromosome 22q11.2 deletion syndrome was markedly increased over the prevalence of polyarticular juvenile rheumatoid arthritis (JRA) in the general population. All 3 patients with polyarthritis had evidence of impaired T cell function. Two of the patients with polyarthritis also had IgA deficiency.

CONCLUSION

The chromosome 22q11.2 deletion syndrome represents a primary T cell disorder which can be associated with a JRA-like polyarthritis. All 3 patients with polyarthritis had evidence of more extensive immunoregulatory derangements than those typically seen in patients with chromosome 22q11.2 deletion, and these derangements may have predisposed to the development of polyarthritis.