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In vitro Lymphoproliferative Assays with HgCl2 Cannot Identify Patients with Systemic Symptoms Attributed to Dental Amalgam
Linköping University, Department of Molecular and Clinical Medicine, Molecular and Immunological Pathology. Linköping University, Faculty of Health Sciences.
Department of Neurology and Neurophysiology and Centre for Environmental Sensitivity, Örebro Medical Centre Hospital, Örebro, Sweden.
Linköping University, Department of Molecular and Clinical Medicine, Molecular and Immunological Pathology. Linköping University, Faculty of Health Sciences.
Department of Transfusion Medicine and Immunohaemotherapy, Örebro Medical Centre Hospital, Örebro, Sweden.
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1999 (English)In: Journal of Dental Research, ISSN 0022-0345, E-ISSN 1544-0591, Vol. 78, no 8, p. 1450-1458Article in journal (Refereed) Published
Abstract [en]

Dental amalgam is suspected, by some exposed individuals, to cause various systemic psychological, sensory, and neurological symptoms. Since not all amalgam-bearers experience such reactions, an individual characteristic—for example, a susceptible immune system—might explain these conditions. In vitro lymphocyte proliferation is a valuable tool in the diagnosis of allergy. With HgCl2 as the antigen, however, the test is hampered, because Hg2+ can cause unspecific lymphocyte proliferation, optimal at 1.4 to 9.5 μg HgCl2/mL. Recently, the use of suboptimal HgCl2 concentrations (≤ 0.5 μg/mL) has been suggested to circumvent these problems. The main aim of this study was to investigate whether patients with systemic symptoms alleged to result from the presence of dental amalgam differ from healthy controls, with reference to in vitro lymphoproliferative responses to HgCl2 ≤ 0.5 μg/mL. Three different test protocols—lymphocyte transformation test (LTT) in micro- and macro-cultures, and the memory lymphocyte immunostimulation assay (MELISA®)—were used. Other immune parameters—such as a standard patch test for dental materials, the number of T- and B-lymphocytes, monocytes, granulocytes, and NK cells in peripheral blood, allergic symptoms, and predisposition-were also investigated. Twenty-three amalgam patients, 30 healthy blood donors with amalgam, ten healthy subjects without amalgam, and nine patients with oral lichen planus (OLP) adjacent to dental amalgam and a positive patch test to Hg0 were tested. None of the investigated immune parameters revealed any significant differences between amalgam patients and controls. The sensitivity of in vitro lymphocyte proliferation ranged from 33 to 67%, with the OLP patients as a positive control group, and the specificity from 0 to 70% for healthy controls with a negative patch test to Hg°. Thus, despite the use of HgCl2 ≤ 0.5 μg/mL, a high frequency of positive results was obtained among healthy subjects with or without dental amalgam. Consequently, in vitro lymphocyte proliferation with HgCl2 cannot be used as an objective marker for mercury allergy in dental amalgam-bearers.

Place, publisher, year, edition, pages
1999. Vol. 78, no 8, p. 1450-1458
National Category
Medical and Health Sciences
Identifiers
URN: urn:nbn:se:liu:diva-25875DOI: 10.1177/00220345990780081101Local ID: 10312OAI: oai:DiVA.org:liu-25875DiVA, id: diva2:246423
Available from: 2009-10-08 Created: 2009-10-08 Last updated: 2017-12-13Bibliographically approved
In thesis
1. The Primary Lymphocyte Culture in the Diagnosis of Drug- and Metal-Induced Allergy
Open this publication in new window or tab >>The Primary Lymphocyte Culture in the Diagnosis of Drug- and Metal-Induced Allergy
2000 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Drugs and metals are examples of xenobiotics that can induce hypersensitivity in humans. These adverse reactions are classified as allergy if repeated exposure leads to the same type of clinical manifestation. Together with the clinical history, the skin test is the most commonly used test for the diagnosis of allergic disease. However, in vivo testing per se has drawbacks such as the risk of potentiation of the allergy or even sensitisation to a given test substance. For this reason in vitro testing is an attractive diagnostic alternative since it does not involve any exposure of the test subject to the allergen.

The lymphocyte transformation test (LTT) has been used to complement the diagnosis of allergy to drugs and metals for more than thirty years. The principle behind this test is to show the presence of allergen-specific memory lymphocytes in peripheral blood, which is a sine qua non of a true allergy. LTT reveals the proliferation of such cells by showing DNA synthesis as the uptake of 3H-thymidine in primary PBMC (peripheral blood mononuclear cell) cultures treated with the allergen. However, LIT has not yet been generally accepted as a stand-alone test in the diagnosis of allergy. One reason for this is that different chemical properties of the allergens may lead to either false positive or false negative LTT responses.

In the present study we investigated allergy to the drug bacampicillin and to the metals Au, Pd, Ni and Hg. Three different protocols for LTT: LIT in micro cultures (LTT-micro), LTT in macro cultures (LTT-macro) and memory lymphocyte immunostimulation assay (MELISA) were compared using a skin test or clinical history as reference methods. LTI showed a sensitivity of 87% and a specificity of 90% when used in the diagnosis of allergy to bacampicillin. When allergy to Au, Pd, Ni and Hg was investigated, the sensitivity was 33- 95% and the specificity 0-79%. There were no significant differences between the test protocols, except that MELISA showed a significantly higher specificity than LTT-micro and LTT-macro when Hg2+ was used as antigen. Even so, this specificity was only 70%, which would result in 30 of 100 healthy subjects receiving a false diagnosis of Hg allergy when using the MELISA protocol. Ni2+ also induced high numbers of false-positive LTI responses, 77-85% patch-test negative subjects showed positive results to these metals. However, group comparisons showed a significantly higher proliferation intensity in allergic than in nonallergic groups for all allergens except Hg2+. Furthermore, only 56% of patients with verified allergy to mercury showed a positive MELISA, a sensitivity that is unacceptably low.

Following these findings, we investigated whether other endpoints than DNA synthesis could be used to discriminate allergic from healthy subjects, using primary PBMC cultures with Hg2+ or Ni2+ as a model system. Analysis of the T-cell receptor Vß profiles of lymphoblasts induced by these metal ions showed individual patterns, and there was no difference between healthy and allergic groups. However, the fraction of CD4+/Vß2+ cells correlated significantly with the proliferation intensity induced by Hg2+ in patients with a verified Hg allergy but not in non-allergic controls. Interestingly, such a correlation was not seen with CD8+/Nß2+ cells. This indicates that Hg2+ does not function as a superantigen, since classical superantigens also stimulate CD8+ lymphocytes. When Ni2+ was used as antigen we found significantly higher IL-10 production in allergic than in non-allergic subjects, despite no significant difference in proliferation intensity between these two groups.

In conclusion, the LTT test is useful for the diagnosis of allergy to bacampicillin. Regarding Au, Pd and Ni the LIT has low validity and can only be used to discriminate groups of allergic from non-allergic individuals. LTT with Hg2+ and Ni2+ is not useful for the diagnosis of allergy to these metals since a high fraction of non-allergic individuals show positive results, irrespective of the test protocol used. This thesis calls for further studies on the usefulness of in vitro IL-10 production for the diagnosis of Ni allergy as well as on the specificity of in vitro induced CD4+N~2+ lymphoblasts from Hg allergic subjects.

Place, publisher, year, edition, pages
Linköping: Linköpings universitet, 2000. p. 69
Series
Linköping University Medical Dissertations, ISSN 0345-0082 ; 635
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-28555 (URN)13708 (Local ID)91-7219-736-6 (ISBN)13708 (Archive number)13708 (OAI)
Public defence
2000-03-31, Berzeliussalen, Universitetssjukhuset, Linköping, 09:30 (Swedish)
Opponent
Available from: 2009-10-09 Created: 2009-10-09 Last updated: 2012-08-09Bibliographically approved

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Cederbrant, KarinHultman, Per

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