The Lymphocyte Transformation Test (LTT) was developed in the 1960s and is primarily used in allergy diagnostics. The LTT test has also been used in the diagnosis of chronic Borrelia burgdorferi infections, which is the cause of Lyme disease. The test is especially important when there are difficulties in diagnosing the disease. What is the LTT test and how to interpret its results?

Contents:

  1. Lymphocyte Transformation Test (LTT) - Application
  2. Lymphocyte transformation test (LTT) - Lyme disease
  3. Lymphocyte transformation test (LTT) - what is it about?
  4. Lymphocyte Transformation Test (LTT) - Results

The lymphocyte transformation test( LTT ) was first described in 1960.

The test is currently used in research and as a diagnostic tool in various fields of medicine, mainly allergology.

Lymphocyte Transformation Test (LTT) - Application

LTT test was used in:

  • assessment of immune system defects, e.g. those manifested by increased susceptibility to infections
  • diagnostics of chronic bacterial (Borrelia, Chlamydia, Yersinia), protozoal (Giardia lamblia) and viral (herpes virus) infections
  • diagnosis of type IV hypersensitivity (allergy) dependent on T lymphocytes to drugs, metals, food additives, molds, foods (e.g. gluten); LTT test has been used in particular for the detection of allergies to dental materials such as dentures or fillings

Lymphocyte transformation test (LTT) - Lyme disease

Diagnostic difficulties related to the diagnosis of Lyme borreliosis force specialists to look for other than recommended laboratory tests. One of them is the LTT test. It is believed that the LTT test may be helpful in:

  • confirmation of active infection in people with positive results of serological tests, but without symptoms indicative of Lyme disease
  • confirmation of active infection in people with negative or borderline results in serological tests, but with clinical symptoms of Lyme disease
  • monitoring the effectiveness of antibiotic therapy
  • Lyme recurrence assessment

You should, howevernote that the LTT test is not a recommended test in the diagnosis of Lyme borreliosis by the National Chamber of Laboratory Diagnosticians, the National Institute of Public He alth and the National Consultant in the field of infectious diseases, because this test still requires validation (i.e. confirmation of its credibility) in this disease entity .

  • Lyme disease - Lyme disease research. Does the tick test make sense?

Lymphocyte transformation test (LTT) - what is it about?

The test is based on the assessment of the reactivity of immune system cells (T lymphocytes of the immune memory) to the tested antigen / allergen, e.g. a drug, a bacterial protein. Immune cells become reactive to a given antigen / allergen after prior contact with it (hence the name T-cells of the immune memory).

For the LTT test, cells are obtained from the patient's peripheral blood taken from a vein. Then, in the laboratory, individual cell fractions are separated from the blood, namely mononuclear cells (lymphocytes and monocytes).

The isolated cells are then grown under appropriate conditions and then stimulated with the specific antigen / allergen. If cells have been in contact with it, they begin to divide and then the intensity of these divisions is measured.

Individual LTT modifications measure the endpoint of cell division differently and can be assessed indirectly by measuring:

  • production of signaling molecules like interferon-gamma (INF-γ) that are produced by dividing cells; another name of this modification of the LTT test is EliSpot
  • receptor activity on the surface of dividing cells, e.g. CD25, CD69, HLA-DR
  • the amount of DNA generated during the synthesis phase that only occurs in antigen / allergen stimulated, dividing T lymphocytes; for this purpose, the newly synthesized DNA strands are labeled, for example, with 3H-thymidine, which is then detected by a special counter

The test is performed in three or four repetitions to increase the reliability of the obtained result.

Worth knowing

The LTT test is a very demanding laboratory test. It requires expensive and modern laboratory equipment and the experience of the staff performing the test.

Due to this fact, the test should be performed only in centers that have experience in performing the LTT test.

Lymphocyte Transformation Test (LTT) - Results

A positive result of the LTT test indicates the presence of immune memory T cells in the blood that had previously been in contact with the tested antigen / allergen. What might indicate a causal relationship-the effect between the examined factor and the patient's symptoms.

The test result shows numerical values ​​expressed as a stimulation index (SI). SI expresses the intensity of division of immune cells relative to the negative control, which in this case are immune cells that have not been stimulated with an antigen / allergen.

An SI score of less than 1 is negative, a score between 2 and 3 is weakly positive (borderline), and a score of more than 3 is positive.

Important

What factors may affect the LTT result?

Taking medications that suppress the immune system, such as steroids (methotrexate, prednisone), may reduce the ability of cells to divide in cell culture and / or the production of cytokines by cells.

References

  1. https: //www.xenodiagnostics.com/lymphocyte-transformation-test.html
  2. Pichler W.J and Tilch J. The lymphocyte transformation test in the diagnosis of drug hypersensitivity. Allergy. 2004 Aug; 59 (8): 809-20.
  3. Rychlik U. et al. Lymphocyte transformation test (LTT) laboratory diagnostics. Journal of Laboratory Diagnostics 2013, 49 (4); 425-428.
  4. Laboratory diagnostics of tick-borne diseases Recommendations of the Working Group: National Chamber of Laboratory Diagnosticians, National Institute of Public He alth-National Institute of Hygiene, National Consultant in the field of infectious diseases, Department of Infectious Diseases and Neuroinfections, Medical University of Białystok, Polish Society of Virology, Warsaw 2014 .
Karolina Karabin, MD, PhD, molecular biologist, laboratory diagnostician, Cambridge Diagnostics Polska A biologist by profession, specializing in microbiology, and a laboratory diagnostician with over 10 years of experience in laboratory work. A graduate of the College of Molecular Medicine and a member of the Polish Society of Human Genetics. Head of research grants at the Laboratory of Molecular Diagnostics at the Department of Hematology, Oncology and Internal Diseases of the Medical University of Warsaw. She defended the title of doctor of medical sciences in the field of medical biology at the 1st Faculty of Medicine of the Medical University of Warsaw. Author of many scientific and popular science works in the field of laboratory diagnostics, molecular biology and nutrition. On a daily basis, as a specialist in the field of laboratory diagnostics, he runs the content department at Cambridge Diagnostics Polska and cooperates with a team of nutritionists at the CD Dietary Clinic. He shares his practical knowledge on diagnostics and diet therapy of diseases with specialists at conferences, training sessions, and in magazines and websites. Especiallyinterested in the influence of modern lifestyle on molecular processes in the body.

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Research