Lymphocyte transformation test

from Wikipedia, the free encyclopedia

The lymphocyte transformation test (LTT) is a laboratory procedure for the detection of antigen-specific T lymphocytes . It is used in immune function diagnostics in medicine . For a few years it has also been used in allergology to detect certain allergic reactions of the delayed type (IV) (e.g. drug allergy, metal allergy) and in pathogen diagnostics ( e.g. if Lyme disease is suspected).

Several university clinics and specialized institutes have standardized the procedure. For drug allergy, the test was included in the recommendations of the German Society for Immunology and Allergology (DGAI) in 2006. For some allergological issues, however, the clinical significance of a proven sensitization is still controversially discussed. For this reason, the LTT should only be used in addition to the patch test for allergological issues or if this cannot be carried out due to contraindications. In the case of systemic sensitizations, for example sensitizations to dentures acquired through the mucous membranes, the LTT seems to have advantages in terms of sensitivity compared to the skin test.

execution

In a first step, the lymphocytes are separated from the other blood cells by centrifugation and several washing processes. Then a nutrient solution and the antigen to be tested are added and the lymphocyte culture is incubated for a few days under optimal growth conditions . A control sample without added antigen is treated in the same way. Radioactive thymine is added 16 hours before the evaluation . The DNA building block thymine is necessary as a substrate for the synthesis of DNA. The radioactivity of the lymphocyte culture is measured and a stimulation index is calculated, which provides information about whether specifically sensitized T lymphocytes are present in the blood sample provided with antigen .

history

The development of the lymphocyte transformation test (LTT) began in the 1960s. The essence of the lymphocyte transformation test formed the fundamental discoveries of Hungerford et al. in 1959, by Nowell in 1960, by Carstairs in 1962 and by Marshall et al. Roberts in 1963, who were able to prove for the first time that the phytohemagglutinin isolated from Phaseolus vulgaris (French bean) can also stimulate large numbers of lymphocytes from human blood to mitosis and blast formation in vitro. The blast formation that occurs on the antigen stimulus in the course of the lymphocyte cultivation is suitable for investigating the in vitro immune reaction. The process was optimized in 2000 by using recombinant interferon-alpha in the test.

criticism

If the complex procedure is poorly carried out, false positive and false negative results are possible. However, this can largely be ruled out by extensive preparatory work for each antigen to be tested. The procedure is accredited according to DIN 15189 at several university hospitals and specialized institutes . Incorrect results are to be expected if the laboratory carrying out the work does not have sufficient experience with cell culture. This is still often the case, which is why the test has so far only been a routine diagnosis in a few institutes. The test is methodologically very demanding and therefore expensive. The statutory health insurances have so far only covered the costs for the issues of immune function and drug allergy as well as under strict indications for contact allergens (e.g. if the skin test cannot be carried out due to contraindications). Since 2009, the LTT has no longer been a service provided by the statutory health insurance as part of the Lyme disease diagnosis. According to the EBM service legend, the lymphocyte transformation test according to item 32532 can not be billed for pathogen diagnosis. The Robert Koch Institute (RKI) has so far only recommended the use of the LTT without restrictions for immune function diagnostics, for the detection of drug allergies and beryllium sensitization. In an evaluation of the LTT procedure updated in 2008, however, the LTT was given advantages in terms of sensitivity and specificity compared to the patch test. In addition, the expert commission of the Robert Koch Institute in Berlin comes to the conclusion that there is a risk of sensitization through the test itself in the epicutaneous test, but not in the LTT. The test for typical environmental allergens has only been validated at a few institutes.

literature

  • C. Schuett: Lymphocyte Transformation Test LTT . In: H. Friemel (Ed.): Immunological working methods . 4th edition. Gustav Fischer, Jena 1991, pp. 349-356.
  • S. Bussa, C. Rumi, G. Leone, B. Bizzi: Evaluation of a new whole blood cytometric lymphocyte transformation test for immunological screening . In: Journal of Clinical and Laboratory Immunology , 1993, 40 (1), pp. 39-46.
  • PA Berg, PT Daniel, N. Brattig: Immunology and detection of drug allergies . In: E. Fuchs, K.-H. Schulz (Ed.): Manuale allergologicum , 1996, IV, 11: 1-13, Dustri, Deisenhofen. Beyer, K., Niggemann, B .; Nasert, S .; Renz, H .; Wahn, U .: Severe allergic reactions to foods are predicted by increases of CD4 + CD45RO + T cells and loss of L-selectin expression. Journal of Allergy and Clinical Immunology , 1997; 99 (4): 522-529

See also

Web links

Individual evidence

  1. ↑ a b Quality assurance in the lymphocyte transformation test (PDF) Addendum to the LTT paper of the RKI commission "Methods and Quality Assurance in Environmental Medicine" Federal Health Gazette 2008; 51: 1070–76
  2. ↑ a b Bundesgesundheitsbl - Gesundheitsforsch - Gesundheitsschutz 51, 2008, 1071-1076
  3. ↑ N. Simon, A. Dobozy, J. Hunyadi: The importance of the lymphocyte transformation test in dermatology In: Occupational dermatoses . 1970; 18: 189-219
  4. ↑ von Baehr: Improving the in vitro antigen specific T cell proliferation assay: the use of interferon-alpha to elicit antigen specific stimulation and decrease bystander proliferation. In: J Immunol Methods . May 2001,1; 251 (1-2): pages 63-71
  5. ↑ apug.de (PDF; 104 kB)
  6. ↑ H. Renz: Short version of the position paper of the DGAI - In-vitro diagnostics of allergic diseases. In: The clinic doctor. 32, 2003, p. 119, doi : 10.1055 / s-2003-39218 .