Tissue transglutaminase autoantibodies in patients with non-Hodgkin's lymphoma. Case reports

Autoantibodies in the Extraintestinal Manifestations of Celiac Disease

Increased antibody reactivity towards self-antigens is often indicative of a disruption of homeostatic immune pathways in the body. In celiac disease, an autoimmune enteropathy triggered by the ingestion of gluten from wheat and related cereals in genetically predisposed individuals, autoantibody reactivity to transglutaminase 2 is reflective of the pathogenic role of the enzyme in driving the associated inflammatory immune response. Autoantibody reactivity to transglutaminase 2 closely corresponds with the gluten intake and clinical presentation in affected patients, serving as a highly useful biomarker in the diagnosis of celiac disease. In addition to gastrointestinal symptoms, celiac disease is associated with a number of extraintestinal manifestations, including those affecting skin, bones, and the nervous system. Investigations of these manifestations in celiac disease have identified a number of associated immune abnormalities, including B cell reactivity towards various autoantigens, such as transglutaminase 3, transglutaminase 6, synapsin I, gangliosides, and collagen. Clinical relevance, pathogenic potential, mechanism of development, and diagnostic and prognostic value of the various identified autoantibody reactivities continue to be subjects of investigation and will be reviewed here.

Autoantibodies in celiac disease

Autoantibody production is an important feature of many autoimmune disorders, signifying a breakdown of immune tolerance to self-antigens. In celiac disease, an autoimmune enteropathy with multiple extra-intestinal manifestations, autoantibody reactivity to transglutaminase 2 (TG2) has been shown to closely correlate with the acute phase of the disease. It serves as a specific and sensitive marker of celiac disease, and is highly useful in aiding diagnosis and follow-up. Immune reactivity to other autoantigens, including transglutaminase 3, actin, ganglioside, collagen, calreticulin and zonulin, among others, has also been reported in celiac disease. The clinical significance of these antibodies is not known, although some may be associated with specific clinical presentations or extra-intestinal manifestations of celiac disease. This review examines the presence of anti-TG2 and other autoantibodies in celiac disease, discussing their diagnostic value, their potential role in disease pathogenesis and current hypotheses that explain how their release may be triggered.

European multi-centre study on coeliac disease and non-Hodgkin lymphoma

INTRODUCTION

Coeliac disease (CD) is associated with an increased risk of non-Hodgkin lymphoma (NHL), but there is little information about whether this is true for clinically silent CD.

OBJECTIVE

To investigate the frequency of CD in two European populations; one with NHL and another derived from the general population.

METHODS

A prospective, multi-centre, case-control study in 10 European countries was conducted between May 1998 and April 2001. A total of 1446 consecutive patients with newly diagnosed NHL aged over 18 years was collected. The control group consisted of a population of 9676 individuals who were screened for CD. The number of patients with a previous diagnosis of CD and those with silent CD detected by screening were determined in the two groups.

RESULTS

The patients with CD had a significantly increased risk of developing NHL [odds ratio (OR) 2.6, 95% confidence interval (CI) 1.4-4.9]. This risk was only present in patients with CD diagnosed clinically before the study (OR 3.3, 95% CI 1.4-7.9), but not in those with silent CD detected by screening (OR 1.3, 95% CI 0.6-2.7).

CONCLUSION

Patients with CD have an increased risk of developing NHL, although this is lower than previously thought. Clinically silent CD is rare in patients with NHL.

[Auto-immune manifestations in Non-Hodgkin's lymphoma]

PURPOSE

A wide spectrum of auto-immune manifestations is frequently reported in non-Hodgkin's lymphoma (NHL). The purpose of the review is to describe the immune manifestations observed in NHL, according to their histological subtype and to discuss the current physiopathological hypothesis with their therapeutic relevance.

CURRENT KNOWLEDGE AND KEY POINTS

Most of the organs can be targeted by an immune process due to the lymphoproliferative disease: they include skin diseases (paraneoplastic pemphigus, vasculitis, urticaria, acrosyndromes), peripheral and central nervous system involvement (polyneuropathy, multifocal neuropathy), haematological manifestations (immune cytopenia, acquired bleeding disorders), rheumatologic diseases (arthritis, systemic vasculitis, myositis) and renal lesion (cryoglobulinemia, glomerulopathies). A higher prevalence of autoantibodies, such as antinuclear antibodies, Antiphospholipid antibodies, or endomysium antibodies, is observed in NHL but usually without clinical manifestations. In B-cell NHL, clinical and biological immune manifestations are more frequently observed in indolent lymphoma than in aggressive NHL. In T-cell NHL, immune manifestations are frequent and polymorphous, preceding usually the diagnosis of lymphoma. The prognosis value of the immune manifestations in NHL is unclear. Immune manifestations can be also be related to the treatment procedure, including fludarabine, Interferon, autograft or Rituximab. The physiopathology of the immune manifestations may involve auto-antibodies production by natural CD5+ autoreactive B-cell from which is issue the proliferation, a lost of immune tolerance, an abnormality in the Fas/Fas Ligand pathway or a chronic antigenic stimulation.

FUTURE PROSPECTS AND PROJECTS

As observed in T-cell lymphoma cases, immunosuppressive treatment can control both immune manifestations and lymphoproliferation, suggesting that lymphoma and auto-immunity may be the two aspects of the same process. The monoclonal antibody anti-CD20 (rituximab), able to suppress the tumoral cells and change the B-cell repertoire is the most promising treatment to cure immune disorders related to NHL. So far, rituximab has been successfully used in mixed cryoglobulinemia and cold agglutinins secondary to NHL.

Anti-human versus anti-guinea pig tissue transglutaminase antibodies as the first-level serological screening test for coeliac disease in the general population

BACKGROUND

So far the reliability of the anti-guinea pig and anti-human tissue transglutaminase antibodies for the coeliac disease diagnosis has been evaluated in selected groups of patients.

AIM

To compare the diagnostic accuracy of anti-human versus anti-guinea pig tissue transglutaminase in the coeliac disease screening of the general population.

SUBJECTS

Two healthy Italian populations living in Marche region and in Western Sardinia.

METHODS

Both anti-guinea pig and anti-human tissue transglutaminase were determined using an enzyme-linked immunosorbent assay-based commercially available kit (Eu-tTG, Eurospital, Trieste, Italy).

RESULTS

During the period 1999-2001, 3541 subjects (1500 from "continental" Italy and 2041 from Sardinia) were screened for coeliac disease using both anti-guinea pig and anti-human tissue transglutaminase as first-level tests. Both these tests were negative in 3439/3541 sera, while 29 resulted positive for both of them and 73 showed discordant results. Overall, 50 intestinal biopsies were performed in 22, 21 and 7 subjects with positivity to both screening tests, to anti-guinea pig and to anti-human tissue transglutaminase alone, respectively. A coeliac disease diagnosis was made in 25 subjects giving an overall prevalence of 1:126 individuals. The anti-tissue transglutaminase specificity and sensitivity were 98 and 92% for guinea pig and 99.6 and 96% for human tissue transglutaminase, respectively.

CONCLUSIONS

The anti-human tissue transglutaminase test should definitely replace the anti-guinea pig-derived one as first-level screening tool for identifying all subjects who need the second-level investigations (small intestinal biopsy).

Tissue transglutaminase antibodies in patients with end-stage heart failure

OBJECTIVE

For celiac disease (CD), screening a trend has recently emerged to measure tissue transglutaminase antibodies (tTGA) by immunoassays instead of the more laborious endomysial antibodies (EmA), as they recognize the same target, tissue transglutaminase (tTG). However, a high rate of false-positive results has been reported in some patient series with diseases known to be associated with CD. Moreover, tTG is a ubiquitous, multifunctional enzyme, overexpressed in experimental models of heart failure. Therefore, we assessed the specificity of tTGA assays in a large series of EmA-negative patients with end-stage heart failure.

METHODS

We studied 288 patients with end-stage heart failure and 60 blood donors. No subject had clinical evidence of CD or IgA deficiency, and all were EmA negative. Serum IgA and IgG tTGA were measured by means of commercial kits using as substrate, either guinea pig or recombinant human tTG. Blocking studies and Western blots were also performed using recombinant human tTG.

RESULTS

All blood donor sera were IgA tTGA negative. IgA tTGA positivity was observed in 47.6% and 49.1% of patients with heart failure using, respectively, guinea pig tTG and recombinant human tTG as substrates. Preincubation of positive sera with recombinant human tTG resulted in 81% blocking of IgA tTGA in immunoassay. Western blot analysis confirmed the presence of antibodies against recombinant human tTG. IgA tTGA-positive sera were also IgG tTGA positive.

CONCLUSIONS

IgA and IgG tTGA occur in a large number of EmA-negative patients with end-stage heart failure, and their presence is unlikely to be caused by concomitant CD.

Comparison of Anti-Transglutaminase ELISAs and an Anti-Endomysial Antibody Assay in the Diagnosis of Celiac Disease: A Prospective Study

Background: Most studies of anti-transglutaminase (anti-tTG) assays have considered preselected groups of patients. This study compared the sensitivity, specificity, and predictive value of an immunofluorescence method for anti-endomysial antibodies (EmAs) and two anti-tTG ELISAs, one using guinea pig tTG (gp-tTG) and the other human tTG (h-tTG) as antigen, in consecutive patients investigated for suspected celiac disease (CD).

Methods: We studied 207 consecutive patients (99 men, 108 women; age range, 17–84 years) who underwent intestinal biopsy for suspected CD. Patients presented with one or more of the following: weight loss, anemia, chronic diarrhea, abdominal pain, dyspepsia, alternating bowel habits, constipation, pain in the joints, and dermatitis. At entry to the study, an intestinal biopsy was performed and a serum sample was taken for IgA EmAs, anti-gp-tTG, and anti-h-tTG.

Results: Intestinal histology showed that 24 patients had partial or total villous atrophy; in these patients the diagnosis of CD was confirmed by follow-up. The remaining 183 patients had villous/crypt ratios that were within our laboratory’s reference values and were considered controls. Serum EmAs, anti-gp-tTG, and anti-h-tTG were positive in all 24 CD patients; in the control group, none were positive for serum EmAs, but 15 of 183 (8.2%) were positive for anti-gp-tTG, and 6 of 183 (3.3%) were positive for anti-h-tTG. Sensitivity was 100% for all assays, whereas specificity was 100% for the EmA, 92% for the anti-gp-tTG, and 97% for the anti-h-tTG assay. The negative predictive value was 100% for all assays; the positive predictive value was 100% for the EmA, 80% [95% confidence interval (CI), 65–95%] for the anti-h-tTG (P = 0.03 vs EmA) and 60% (95% CI, 44–76%) for the anti-gp-tTG assay (P = 0.0002 vs EmA). Areas (95% CIs) under the ROC curves were 0.987 (0.97–1.0) for anti-h-tTG and 0.965 (0.94–0.99) for anti-gp-tTG. Most of the patients testing false positive for anti-tTG had Crohn disease or chronic liver disease.

Conclusions: Although both anti-tTG ELISAs showed optimum sensitivity, their lack of specificity yielded positive predictive values significantly lower than those for the EmA assay.

New developments in childhood celiac disease

Celiac disease (CD) is one of the most common lifelong disorders in Europe and the United States, in both children and adults. It is an immune-mediated enteropathy triggered by the ingestion of gluten in genetically susceptible individuals. This review addresses new developments in CD with respect to pediatric patients and emphasizes the need for awareness among health-care professionals. The epidemiology, pathophysiology, diagnosis, and clinical spectrum of CD in children are highlighted.