Effector cell typing

The T lymphocytes involved in an existing sensitisation to dental restoration materials are characterised using effector cell typing.

Since the mid 1980s, the TH1/TH2 paradigm has dominated our understanding of the immunological responses in T cell sensitisations. TH1-dominant sensitisations are characterised by the involvement of IFN-γ producing effector T cells which are able to trigger inflammation. In contrast, TH2 lymphocytes slow down an allergen-induced immune response and thus have a balancing effect and preserve tolerance.

In recent years, it has become increasingly clear that TH2 cells include two functionally different cell populations, namely the actual TH2 cells (trigger immediate-type allergic reactions) and a cell population of regulatory T cells (Treg cells) which are the actual T suppressor cells.

What significance does this have for routine diagnostics?

The lymphocyte transformation test (LTT) detects immunological sensitisation (type IV sensitisation), that is, it reveals whether the patient has allergen-specific T lymphocytes in his or her blood. A negative result rules out sensitisation to the allergens tested. A positive result means that the patient’s immune system recognises the particular allergen.

This can happen in two ways:

  1. Existing TH1-dominant effector cells are activated. This leads to an inflammation. 
  2. Regulatory T cells (Treg) are primarily involved, the immune activation is slowed down, the allergen is tolerated despite the sensitisation. An inflammation does not develop, at least not at the moment.

The lymphocyte transformation test does not differentiate between the presence of TH1 or regulatory T cells in the patient. Therefore, a positive LTT result is also not able to prove that this sensitisation will be associated with a current inflammation when contact is made with the allergen concerned. The latter is always the case when TH1 cells dominate.

When is effector cell typing indicated?

It is indicated exclusively for curative clinical issues as a supplement to the LTT, that is, when there are symptoms for which possible material intolerances are considered the cause. Effector cell typing is included in cases in which the dentist would like to only make decisions regarding therapy with a known existing sensitisation if the causal relationship between a sensitisation and existing symptoms has been verified as much as possible.

For preventive testing, knowing the current TH1/Treg ratio is not important, however. In case of an existing sensitisation, the dentist would avoid the material concerned and seek alternatives because the TH1/Treg ratio is in no way constant and can change over the course of a lifetime.

Because negative effector cell typing (independent of the cytokine spectrum selected) does not reliably exclude sensitisation, this (more expensive) test is not an alternative to the LTT but instead supplements it.

How is effector cell typing done?

The immune cells of the patient are stimulated in the laboratory with the ‘suspected’ allergen/hapten. If specific T cells are present (that is, if there is an existing sensitisation), these cells are activated, which means they produce cytokines and start to replicate.

While this cell division is measured using the LTT, the cell culture is stopped after 24 hours for effector cell typing and the cytokines produced after stimulation are analysed in the supernatant using ELISA. If no cytokines can be detected in an unstimulated basal cell culture carried out in parallel, the quantities of cytokines measured can be attributed solely to the contact between the immune cells and the particular allergen.

The following are measured:

  • IFN-γ - Marker for allergen-specific TH1 cytokines
  • IL-10 - Marker for allergen-specific regulatory T cells (Treg)

Additionally for specific clinical questions:

  • IL-2 und TNF-α, which are released by TH0 and TH2 cells

Why is effector cell typing not suitable as a screening test?

This is because even if there are negative results for all 4 cytokines, a latent sensitisation cannot be ruled out! Apart from this, the fact that a cytokine response does not appear to be obligatory, particularly for Treg and TH2 cells, is primarily because too few T lymphocytes are activated with moderate sensitisations to be able to generate a measureable cytokine excess. A ‘cytokine excess’ means that after 24 hours of cell culture, we can only measure those cytokines that have not been ‘used’ again by the activated T lymphocytes themselves. Particularly with milder sensitisations, the sensitivity of effector cell typing is insufficient to detect latent allergic sensitisations which are important from a preventive point of view.

Because effector cell typing is used not as a screening test but instead carried out after the LTT, the cytokines IFN-γ and IL-10 are adequate for routine diagnostics.

Notes on the results: Allergen-induced cytokine pattern from a patient with type IV sensitisation to nickel and gold (confirmed in LTT). The results suggest that gold is actually involved in the inflammatory response in this case but not nickel.

The following constellations may occur and are interpreted as follows:

IFN-γ positive / IL-10 negative:pro-inflammatory effector cell response
IFN-γ positive / IL-10 positive:intermediary type, both cell types involved. The clinical relevance depends on the level of the cytokine responses although any positive IFN-γ value indicates that pro-inflammatory effector cells are involved!
IFN-γ negative / IL-10 positive:
only suppressive Treg cells present, no pro-inflammatory effector cell response but latent sensitisation
IFN-γ negative / IL-10 negative:no sensitisation or only TH2 T cells present

Sample materials required

About 5 mL heparin blood for each allergen or hapten. The heparin Monovettes in the LTT collection set can be used. We are also happy to send you individual collection tubes. The laboratory must receive the samples within 24 hours of collection. The blood should be stored and transported at room temperature.

Literature