Lymphocyte transformation test (LTT)

What is the lymphocyte transformation test (LTT)?

LTT - history

Currently, the LTT is the only laboratory method to test for specific cellular sensitization.
First described in 1960, the test has evolved into a reproducible and highly sensitive method, taking advantage of the development in cell culture techniques and analytical methods.
Today its use extends beyond medical-biological research into routine diagnostic testing.
The test is based on the principle of antigen/allergen-specific induction of cell division in lymphocytes following contact with their “fitting” antigen.
A positive reaction in the LTT indicates the presence of antigen-specific lymphocytes (memory cells) in the patient’s blood.

What are the differences between today’s LTT and earlier versions of the test?

Around the year 2000, the LTT's sensitivity was still comparatively low. In type IV allergy testing, the LTT was at best equal to the skin test, if not inferior.
In these early years, its specificity in infection diagnostic testing was of concern.
It was relatively low as the quality of the test antigens available at that time was poor.
Frequently they triggered weakly positive and thus inconclusive reactions, making the interpretation of the results difficult.
This has changed dramatically in recent years.
Today, the LTT technologies used in specialised immunological laboratories are very reliable and offer high sensitivity and specificity.

LTT - importance / significance

Advances in cell culture methods and media, the quality of allergens and antigens used for cell stimulation and, last but not least, the fundamentally improved measuring methods available today have all contributed to this development.
The liquid scintillation counters used in the past to measure 3H-thymidine activity have been replaced by advanced solid-phase β counters, not requiring any subsequent manipulation of cultured cells.
Furthermore, the LTT now uses so-called micro-culture techniques which by allowing multiple test runs greatly enhance the reliability of the results.
Adding genetically engineered interferon-α to the cell culture has contributed to the development of this micro-culture technique among other modifications (von Baehr et al, J. Immunol. Methods 2001; 251: 63-71).
With the introduction of this optimised LTT version into routine testing in 2005, the test’s sensitivity and specificity greatly improved, especially in comparison with the MELISA methods that were still used at that time.
The lymphocyte transformation test is a demanding laboratory technology requiring not only expensive modern laboratory equipment but also laboratory staff with great experience and diligence. With the LTT, only few steps of the process can be automated. Even in today’s age of modern technology, good old manual processing by experienced staff trained in cell culture techniques is at the heart of cell cultures.
In addition, the level of standardisation in the respective laboratory has a significant impact on the analytical quality, as has the way how the methods were established and validated for each task. For this reason, cell-based analytic methods should only be used by specialized laboratories and institutes focussed on this technologies where these methods are accredited according to DIN 15189 by the National Accreditation Body for the Federal Republic of Germany (DAkkS).
The lymphocyte transformation test was first accredited in accordance with DIN 15189 at the Institut für Medizinische Diagnostik as early as 2004.
In its currently available modern version, the lymphocyte transformation test has firmly established itself as a medical diagnostic testing method for various diseases.

The LTT’s range of indications comprises 3 key areas of medical diagnostics:

  1. Immunodeficiency
    Detection of deficiencies and functional impairments of the cellular immune system. See information.
  2. Pathogens
    Detection of the activity of chronic, persistent infections based on pathogen-specific T cell response (Borrelia, Chlamydia, Yersinia, Giardia lamblia, Herpes viruses, among others). See information.
  3. Type IV allergy
    Detection/exclusion of allergic sensitization of the cell-mediated type (type IV allergy) e.g. to medications, metals, acrylates, environmental pollutants, moulds or food allergens. See information.

LTT - procedure

Performing the LTT

During the first step of the lymphocyte transformation test, the lymphocytes and monocytes (also referred to as mononuclear cells) are extracted by density gradient centrifugation using a Ficoll gradient.
Following several cleaning runs, the cells are collected in a special culture medium (with added IFN-α, among others) and then cultured.
The antigens to be tested are pipetted to the cells in triplicate and incubated under optimum growth conditions for 5 days. Subsequently, 3H-thymidine is added and the cells are cultured for further 12 hours.
During the phase of DNA synthesis, which only occurs in antigen/allergen-stimulated dividing lymphocytes, 3H-thymidine T* is integrated into the newly produced DNA strands and can then be quantified using a beta counter.
To show the result, the induced lymphocyte proliferation is calculated in comparison with the spontaneous proliferation (blank) and the result is reported as stimulation index (SI).
The stimulation index is the ratio of the proliferation rates in the stimulated test run and the non-stimulated blank.

LTT - analysis profile

The Institut für Medizinische Diagnostik offers the following LTT profiles:
Each of the antigens and allergens included in the profile can also be tested individually.

Immune function testing
LTT Immune FunctionTesting of functional immune competence with antigens / mitogens Tetatoxoid, influenza, cytomegalovirus (CMV), varicella-zoster virus, streptokinase, candida, PWM
LTT Immune StimulationTest includes the LTT Immune Function (see above) PLUS the testing of immunomodulators at the requester’s choice (please enquire with the lab about the standardised preparations available)
Pathogen testing
LTT-Borreliaspecific activity against recombinant OspC, B. sensu strictu, B. afzelii, B. garinii
LTT-Chlamydia trachomatisspecific activity against Chlamydia trachomatis antigen
LTT-Chlamydia pneumoniaespecific activity against Chlamydia pneumoniae antigen
LTT-Yersiniaspecific activity against Yersinia enterocolitica antigen
LTT-Lambliaspecific activity against Giardia lamblia antigen
LTT-Helicobacterspecific activity against Helicobacter pylori antigen
LTT-Staphylococcusspecific activity against Staphylococcus aureus antigen
LTT-Streptococcusspecific activity against streptokinase
LTT-Candidaspecific activity against Candida albicans antigen
LTT-Herpes virusesCMV, EBV, VZV, HHV6, HSV1, HSV2
Individual analyses
LTT-HSV Ispecific activity against Herpes simplex antigen
LTT-HSV IIspecific activity against genital herpes antigen
LTT-VZVspecific activity against varicella-zoster antigen
LTT-CMVspecific activity against cytomegalovirus antigen
LTT-EBVspecific activity against Epstein-Barr virus antigen
LTT-HHV 6specific activity against human herpes virus-6 antigen
LTT-HHV 8specific activity against human herpes virus-8 antigen
Allergy Testing
Drug allergy
LTT Medicationsdetection of type IV sensitization (medications can be sent in as well)
LTT Ointment BasesPetroleum jelly, lanolin, sorbiton, polyethylene glycol, triethanolamine, Eucerin, coconut oil, isopropyl myristate
Material intolerance
LTT Dental CheckMetals: gold, nickel, palladium, chromium, cobalt, platinum, mercury, copper, silver, tin
plastics: methyl methacrylate (MMA), hydroxyethyl methacrylate (HEMA), TEGDMA, BISGMA
LTT Metalsmercury, copper, silver, tin, ethylmercury, gold, nickel, palladium, chromium, cobalt, molybdenum, aluminium, platinum, cadmium
LTT Endoprostheticschromium, cobalt, molybdenum, nickel, titanium, vanadium, niobium, aluminium, zirconium (IV) oxide, methyl methacrylate, N,N-dimethyl-p-toluidine, benzoyl peroxide, hydroquinone, gentamicin
LTT Gold Alloygold, silver, platinum, copper, palladium, tin, gallium, indium, iridium, ruthenium, rhodium, tantalum
LTT Amalgammercury, copper, silver, tin, organic mercury compounds (ethyl-, phenyl- and methyl mercury)
LTT PlasticsTEGDMA, BISGMA, BISDMA, HEMA, methyl methacrylate (MMA), diurethane dimethacrylate (UDMA), ethylene glycol dimethacrylate, butanediol 1,4-methacrylate, hydroquinone, N,N-dimethyl-4-toluidine, benzoyl peroxide, formaldehyde, phthalate, camphorquinone
LTT Titaniumtitanium, nickel, vanadium, aluminium
LTT Ceramics/Cementsvanadium, aluminium, titanium, cobalt, chromium, barium, silicon, cerium, boron, manganese, antimony, phosphate cement (Harvard), glass ionomer base cement (Ketac-Bond)
LTT Root Canal Filling Materialsraw gutta-percha, Balsam of Peru, eugenol, PDMS, silicone oil, bismuth oxide, silver, turpentine oil, colophony, triethanolamine, peanut oil, paraformaldehyde, bisphenol A, epichlorohydrin
LTT Native MaterialsTesting of co-supplied materials which are prepared in the laboratory for analysis (e.g. material samples, cements, cosmetic products, solvent mixtures, etc.)
Environmental Pollutants / Moulds
LTT MCS Environmental Factorsnickel, mercury, latex, PCP, PCB, permethrin, formaldehyde, methyl methacrylate, Aspergillus fumigatus, Penicillium chrysogenum, phthalic anhydride, dichlofluanid, PAK mix, 1,6-diisocyanatohexane
LTT Environmental Pollutantsformaldehyde, BTX, CKW, lindane, PAK mix, PCB, PCP, permethrin, latex, 1,6-diisocyanatohexane, phthalic anhydride, dichlofluanid
LTT Flame RetardantsTris(2-chloroethyl) phosphate (TCEP), tris(2-butoxyethyl) phosphate (TBEP), tris(2-ethylhexyl) phosphate (TEHP)
LTT PlasticisersPhthalic anhydride, diethyl phthalate, dimethyl phthalate, dibutyl phthalate, dioctyl phthalate
LTT MouldsAspergillus fumigatus, Penicillium chrysogenum, Trichophyton mentagrophytes, Cladosporum herbarum, Mucor mucedo, Rhizopus nigricans, Stachybotris spp., Botrytis cinerea, Alternaria alternate, Candida albicans (yeast)
LTT Berylliumberyllium
Food Intolerance
LTT Food screening 74 food item group testing + nickelMeat: pig, chicken, beef, turkey, mutton (lamb), goose, duck
Fish: trout, eel, halibut, salmon, cod, carp, tuna, herring
Seafood: lobster, shrimp, crayfish, sole
Cereals: wheat, barley, rye, oat, rice, spelt, corn, soy
Brain food: Black tea, hops, cocoa beans, coffee beans, brewer's yeast
Milk: milk protein, α-lactalbumine, β-lactoglobulin, casein, BSA (bovine serum albumin)
Nuts: peanut, walnut, hazelnut, Brazil nut, pistachio, almond, cashew nut
Garden fruits: apple, pear, strawberry, peach, grapes
Citrus fruits: Orange, grapefruit, lemon, pineapple, mandarin, avocado, kiwi fruit, banana
Spices: pepper, paprika, coriander, aniseed, cinnamon, vanilla, garlic
Vegetables: pea, carrot, potato, cauliflower, celery, asparagus, spinach, tomato, onion
Hen’s egg: egg yolk, egg white as well as baker's yeast as individually tested allergen and nickel as potent contact allergen
LTT Food TOP25cow’s milk, hen’s egg, wheat, rye, corn, spelt, carrot, potato, celery, spinach, tomato, apple, peach, orange, kiwi fruit, cod, tuna, beef, pork, chicken, paprika, hazelnut, peanut, baker’s yeast
LTT Gluten (gliadin)Sensitisation to gliadin


Please download the LTT - analysis profile here