Polymorphisms in inflammatory cytokines and Fcgamma receptors in childhood chronic immune thrombocytopenic purpura: a pilot study

Interleukin-1beta exon 5 and interleukin-1 receptor antagonist in children with immune thrombocytopenic purpura

Immune thrombocytopenic purpura (ITP) is associated with cytokine response and dysregulation of the cytokine network. We investigated the polymorphisms of interleukin (IL)-1beta exon 5 and IL-1 receptor antagonist (IL-1 Ra) in 50 children with acute ITP, in 30 children with chronic ITP, and in 100 healthy children by polymerase chain reaction-based restriction analysis. No significant differences in either genotype distribution (P=0.52) or allelic frequencies (P=0.70) were found among children with acute ITP, chronic ITP, or controls for IL-1beta exon 5. However, significant differences in genotype distribution (P=0.02) and the allelic frequencies (P=0.007) were found among children with acute ITP, chronic ITP, and controls for IL-1 Ra. We found that the IL-1 Ra but not IL-1beta gene polymorphism was associated with childhood ITP. This finding suggests that the IL-1 Ra gene polymorphism is implicated in the pathophysiology of childhood ITP.

Development and research in idiopathic thrombocytopenic purpura: an inflammatory and autoimmune disorder

Bleeding and isolated thrombocytopenia in idiopathic thrombocytopenic purpura (ITP) are phenomena of a transient or long-term disturbed immune response. Since 1980, ITP has become a model for targeted therapeutic immunomodulation with still unclear mechanisms of action. The systematic analysis of ITP aims to determine more clearly defined patient subgroups for targeted therapy and to explore the complex immune disturbances in this autoimmune disorder.

Distribution of the FcgammaRIIIa 176 F/V polymorphism amongst healthy Chinese, Malays and Asian Indians in Singapore

AIMS

To determine and compare the distribution of the FcgammaRIIIa 176 F/V polymorphism across three ethnically distinct populations (Chinese, Asian Indians and Malays) in Singapore.

METHODS

The FcgammaRIIIa 176 F/V polymorphism was genotyped by direct sequencing from genomic DNA samples obtained from normal healthy Chinese, Asian Indians and Malays (n = 192 from each population).

RESULTS

The allelic frequencies of the high binding affinity FcgammaRIIIa 176 V allele for Chinese, Asian Indians and Malays were 35%, 33% and 46%, respectively (F allele frequencies were 65%, 67% and 54%, respectively). Genotype distributions were found to conform to the Hardy-Weinberg law (P > 0.05) in each group. chi(2) comparisons revealed significant differences in the genotype distributions of the FcgammaRIIIa 176 V/F polymorphism of Malays from the other two populations (Chinese and Asian Indians). However, no significant difference in the genotype distributions of the FcgammaRIIIa 176 V/F polymorphism was observed between Chinese and Asian Indian populations.

CONCLUSIONS

The genotype distributions of the FcgammaRIIIa 176 V/F polymorphism in healthy Malays are significantly different from both Chinese and Indians. These observations provide the fundamentals on which future disease associations may be built and also present important implications for the design of therapeutic regimens amongst various ethnic groups.

Recent advances in the treatment of childhood immune thrombocytopenic purpura

Immune thrombocytopenic purpura (ITP), the most common bleeding disorder in childhood, is a benign condition that typically resolves within 6 months following diagnosis. While all would agree on drug treatment for children with severe hemorrhage, management strategies of the minimally symptomatic child with a very low platelet count can vary widely. The case for treatment is based primarily on the risk for the uncommon complication of intracranial hemorrhage or other serious bleeding. Numerous clinical studies clearly indicate that immune globulins (intravenous immune globulin [IVIg] or anti-D) and corticosteroid therapy (prednisone and megadose methylprednisolone) are effective in rapidly raising platelet counts. However, physicians must ultimately decide whether to use drug therapy for a patient with minimal symptoms and low platelet count or adopt an "observation-only" approach. With this background, three fundamental questions emerge when evaluating different clinical strategies and potential outcomes: (1) Which children with ITP need treatment? (2) Which pharmacologic agent best accomplishes the goals of drug treatment? (3) Can physicians better predict the outcome of treatments?

The pathogenesis of immune thrombocytopaenic purpura

Immune thrombocytopaenic purpura (ITP) is an autoimmune bleeding disease that is rarely fatal. However, in many adults treatment is unsatisfactory, with as much morbidity from the immunosuppressive effects of treatment as from bleeding. Identifying the underlying disease process should help us to identify more targeted therapies and improve not only the treatment but also the quality of life of patients with this disorder.

Immune Thrombocytopenic Purpura of Childhood

Immune mediated thrombocytopenia (ITP) is a common manifestation of autoimmune disease in children. Although patients often present with bruises, petechiae, and some mucosal bleeding, the incidence of life-threatening hemorrhage is rare (0.2–0.9%) but can be fatal when presenting in vital organs. A wide range of therapeutic regimens are currently in use, including observation alone, as the majority of children recover within 4–6 months regardless of treatment. A growing understanding of the pathophysiology of acute ITP in children has not impacted the controversy surrounding treatment, but has clarified the mechanism of action of the most frequently used agents in chronic ITP. Newer monoclonal antibodies such as Rituxan have proved very useful in chronic or refractory ITP and studies are ongoing to determine the best regimens using this form of immune modulation. Splenectomy and newer agents to boost platelet production are also under study in chronic ITP. Neonates may also have a form of immune thrombocytopenia with extensive bruising and thrombocytopenia called neonatal alloimmune thrombocytopenic purpura (NATP). Rather than autoantibodies, the platelet destruction is secondary to transplacental maternal IgG alloantibodies. During pregnancy mothers may become sensitized to platelet membrane antigens present on fetal platelets. These antibodies may result in serious bleeding, including intracranial hemorrhage in the perinatal period. Once identified, these mothers may require treatment during future pregnancies to minimize serious bleeding in the fetus and neonate. Treatment in utero and immediately following delivery is focused on restoring neonatal platelets to a safe level and preventing life-threatening bleeding.

The association between fcgammaRIIIB polymorphisms and systemic lupus erythematosus in Korea

Polymorphisms of FcgammaR have been proposed as genetic factors that influence susceptibility to SLE. FcgammaRIIIB polymorphism in systemic lupus erythematosus (SLE) have been studied in various populations, but the results were inconsistent. The aim of this study was to determine the association of FcgammaRIIIB polymorphism in Korean lupus patients. One-hundred and eighty-three SLE patients (166 female, 17 male) meeting 1982 ACR criteria and 300 Korean disease-free controls were enrolled. Genotyping for the FcgammaRIIIB NA1/NA2 was performed by PCR of genomic DNA using allele-specific primers. There was no significant skewing in the distribution of the three FcgammaRIIIB genotypes, and alleles between SLE and the controls. The frequency of FcgammaRIIIB genotypes in SLE patients and controls was FcgammaRIIIB NA1/NA1 27.9% versus 26%, NA1/NA2 55.2% versus 51.7%, NA2/NA2 16.9% versus 22.3%, respectively. The gene frequencies of NA1 allele were 0.56 in the SLE and 0.52 in controls, respectively. Among clinical manifestations, thrombocytopenia was more common in FcgammaRIIIB NA2/NA2 genotype (P = 0.04, OR 2.4, 95% CI 1.0-5.4), and NA2 allele (P = 0.03, OR 1.7, 95% CI 1.1-2.8). Although FcgammaRIIIB polymorphism was not associated with the development of SLE in Korean, thrombocytopenia was associated with FcgammaRIIIB NA2/NA2 genotype, and NA2 allele.

Interleukin 4, interleukin 6 and interleukin 10 polymorphisms in children with acute and chronic immune thrombocytopenic purpura

Immune thrombocytopenic purpura (ITP) is an immune-mediated disorder. We investigated the polymorphisms of interleukin (IL)-4 intron 3, IL-6 (-572 G/C), and IL-10 (-627 C/A) in 50 children with acute ITP, 30 children with chronic TIP, and 100 healthy individuals. There were significant differences in the RP1/RP2 genotype proportion (P = 0.04) and the RP2 allelic frequency (P = 0.03) of IL-4 intron 3 and the A/C genotype proportion (P = 0.01) of IL-10 (-627) between children with chronic ITP and controls. This finding suggests that the IL-4 intron 3 and IL-10 (-627) polymorphisms contribute to the susceptibility of developing childhood chronic ITP.

Platelet count, previous infection and FCGR2B genotype predict development of chronic disease in newly diagnosed idiopathic thrombocytopenia in childhood: results of a prospective study

About 25-30% of children with acute idiopathic thrombocytopenia (ITP) develop chronic disease. It is not well known which patient characteristics influence the course of the ITP. A prospective study in 60 children with newly diagnosed ITP was performed. The aim of the study was to identify patient characteristics at the onset of thrombocytopenia that predicts the progression to chronic ITP. Clinical data and blood samples were collected at several time points during the first 6 months of the disease. Variables predicting chronic disease, as calculated in a multivariate logistic regression analysis, were a platelet count >10 x 10(9)/l at the onset [odds ratio (OR) 1.1, 95% confidence interval (CI) 1.01-1.14], the absence of infection shortly before the onset of the disease (OR 4.8, CI 1.16-19.57) and FGR2B-232I/T genotype (OR 7.9, CI 0.96-65.27). The latter may point at an immune-modulating role of Fc gamma RIIb in ITP. Although only three patients had serious bleeds, 35 patients received immune-modulating treatment for low platelet counts only. Seventeen patients were treated with intravenous immunoglobulin (IVIG) and 18 patients received corticosteroids. Patient variables did not differ between these treatment groups. However, patients receiving IVIG had significantly lower risk for chronic disease.

Single nucleotide polymorphisms of the inflammatory cytokine genes in adults with chronic immune thrombocytopenic purpura

Single nucleotide polymorphisms (SNPs) of inflammatory cytokine genes were examined in 84 adult Japanese patients with chronic immune thrombocytopenic purpura (ITP) and 56 race-matched healthy controls. The SNPs examined were within the genes encoding tumour necrosis factor (TNF)-alpha (-238 G/A and -308 G/A), TNF-beta (+252 G/A), and interleukin (IL)-1beta (-511 C/T and +3953 T/C). Of these SNPs, the frequency of the TNF-beta (+252) G/G phenotype was significantly higher in ITP patients than in healthy controls (21% vs. 7%, P = 0.04, odds ratio = 3.6, 95% confidence interval 1.1-11.1), while no significant association was detected for the other SNPs. The distribution of the TNF-beta (+252) phenotype was not associated with human leucocyte antigen class II alleles or the therapeutic response in ITP patients. The frequency of circulating anti-glycoprotein IIb/IIIa antibody-producing B cells was significantly higher in ITP patients with the TNF-beta (+252) G/G phenotype than in those with the G/A or A/A phenotype (11.9 +/- 4.9 vs. 6.8 +/- 4.9 and 3.7 +/- 2.8 per 10(5) peripheral blood mononuclear cells; P = 0.02 and P < 0.001, respectively). These findings suggest that the SNP located at TNF-beta (+252) contributes to susceptibility to chronic ITP by controlling the autoreactive B-cell responses to platelet membrane glycoproteins.

The etiology of childhood immune thrombocytopenic purpura: how complex is it?

Recent developments in genomics and basic immunology have provided a new set of tools for investigation into the etiology and treatment of childhood immune thrombocytopenia purpura (ITP). The genomic revolution is generating a catalog of germ-line common genetic variants, some of which could influence the susceptibility or outcome of ITP. Similarly, in vitro analyses and animal models have been employed to probe the basic alterations underlying ITP. The emergence of a more refined understanding of complex diseases such as ITP has important implications for prevention, therapy, and follow-up. The relative contribution of the genetic component and its interaction with the strong environmental stimulus, such as an acute, antecedent viral infection, remains to be determined.

Role of transforming growth factor-beta 1 gene polymorphisms in childhood idiopathic thrombocytopenic purpura

PURPOSE

To investigate whether transforming growth factor-beta 1 (TGF-beta 1) gene polymorphisms have a role in the development, clinical progress, and treatment response in children with idiopathic thrombocytopenic purpura (ITP).

PATIENTS AND METHODS

Thirty-five children with acute ITP, 40 children with chronic ITP, and 97 healthy children were enrolled. After genomic DNA was extracted, TGF-beta 1 gene 509 (C-->T), codon 25 (Arg-->Pro), and codon 10 (Leu-->Pro) polymorphisms were studied using a coupled polymerase chain reaction-restriction enzyme digestion method.

RESULTS

The genotype and allele frequencies of TGF-beta 1 polymorphisms between acute ITP, chronic ITP, and control group did not differ significantly. No significant association was found between TGF-beta 1 polymorphisms and therapy response.

CONCLUSIONS

These results demonstrate that the frequency of TGF-beta1 gene 509 (C-->T), codon 25 (Arg-->Pro), and codon 10 (Leu-->Pro) polymorphisms and alleles do not play a role as a genetic risk factor in the development and clinical progress of ITP. Different results may be obtained with further studies involving larger patient populations and other TGF-beta 1 gene polymorphisms.

Idiopathic thrombocytopenic purpura of childhood: a problem-oriented review of the management

Idiopathic thrombocytopenic purpura (ITP) is an often, but not always, self-limited bleeding disorder of childhood of unknown etiology. Duration of more than 6 months defines the chronic form and this occurs in approximately 20% of children and is the common form of the disorder in adults. At initial diagnosis, neither the individual bleeding risk nor the form of the disease, acute or chronic, is predictable, which exposes doctors and parents to fear of life-threatening bleeding. Consequently a majority of children will receive platelet-enhancing therapy to prevent major bleeding manifestations. Prophylactic interventions have proven to be effective in raising the platelet count within a short time period in several prospective trials, however two questions may be raised, (1) whether a rapid platelet increase efficiently prevents serious bleeding and (2) whether such a prophylactic intervention is of clinical value. Furthermore, a small subgroup of patients with major bleeding manifestations seems to be treated inadequately, since patients of this subgroup may bleed in spite of platelet-enhancing therapy. Clinical trials with long-term follow-up are needed, using clinical parameters as study endpoints, to answer the question of which subgroup of children with ITP should be treated upfront with platelet-enhancing therapy.

IgG Fc receptor polymorphisms in human disease: implications for intravenous immunoglobulin therapy

Polymorphisms of human Fc receptors (FcRs) have been described that are associated with the development or progression of autoimmune diseases. The FcR polymorphisms affect the affinity with which FcRs interact with immunoglobulin molecules. Intravenous immunoglobulin is administered as therapy for many autoimmune diseases and might exert its effects by interacting with FcRs. Thus, FcR polymorphisms might influence the efficacy of intravenous immunoglobulin therapy for patients with certain autoimmune diseases. In this article we review FcR polymorphisms in relation to autoimmune diseases for which intravenous immunoglobulin is used therapeutically.

FcgammaR polymorphisms: Implications for function, disease susceptibility and immunotherapy

Leukocyte Fcgamma receptors (FcgammaR) confer potent cellular effector functions to the specificity of IgG. FcgammaR-induced leukocyte functions, including antibody-dependent cellular cytotoxicity, phagocytosis, superoxide generation, degranulation, cytokine production and regulation of antibody production, are essential for host defense and immune regulation. The efficacy of IgG-induced FcgammaR function displays inter-individual heterogeneity due to genetic polymorphisms of three FcgammaR subclasses, FcgammaRIIa (CD32a), FcgammaRIIIa (CD16a), and FcgammaRIIIb (CD16b). FcgammaR polymorphisms have been associated with infectious and autoimmune disease, or with disease severity. FcgammaR polymorphisms may furthermore serve as markers for therapeutic efficacy and side-effects of treatment with monoclonal antibodies. In this review, FcgammaR function and the relevance of FcgammaR polymorphisms as prognostic markers for inflammatory disease and antibody-based immunotherapy are discussed.

Fcgamma receptor IIa and IIIa polymorphisms in childhood immune thrombocytopenic purpura

Fcgamma receptor-mediated destruction of autoantibody-sensitized platelets is central to the immune pathophysiology of childhood immune thrombocytopenic purpura (ITP). Allelic variants exist among the random population for some Fcgamma receptors. The variants represent single nucleotide polymorphisms, leading to functional differences in the ability to bind immunoglobulin (Ig)G or IgG subclasses. The genotypic frequencies for two Fcgamma receptor single nucleotide polymorphisms, FcgammaRIIa-131 arginine (R) versus histidine (H) and FcgammaRIIIa-158 valine (V) versus phenylalanine (F) were examined in 98 children diagnosed with childhood ITP. The genotype frequencies were compared with those of 130 healthy control subjects. Chi-square analysis was used to determine whether the allelic frequencies of the high-affinity receptor variants were associated with childhood ITP. Both the FcgammaRIIa-131H and the FcgammaRIIIa-158V were significantly over-represented in children with ITP versus the control subjects (P-values 0.03). The same statistical difference was noted with the combined FcgammaRIIa-131H and FcgammaRIIIa-158V allelic gene frequencies. There was no statistical difference between children who later developed chronic ITP compared with children with acute ITP, suggesting that additional factors are responsible for the development of the chronic form of the disease. These observations underscore the importance of Fcgamma receptor-mediated cell clearance in childhood ITP.