1- What is a COVID Immunity Test (ELISPOT) and what does it consist of?
The COVID Cellular Immunity Test is performed through the ELISPOT test. This test is based on enzyme-linked immunoadsorption assay (ELISA) and is designed to study the cellular immune response.
At Life Length we measure that cellular immune response by detecting two types of cytokines.
Cytokines are small proteins crucial for controlling the growth and activity of other immune system cells (T lymphocytes), which causes the response to be amplified.
The two cytokines that we quantify in Life Length are:
- Interferon-gamma (IFN-γ): is a cytokine involved in multiple processes and at different points in the activation of the immune system, making it essential in the response to pathogens, especially viruses. It is secreted mainly by activated T lymphocytes and Natural Killer (NK) cells.
- Interleukin 2 (IL-2): this cytokine induces the proliferation and activation of other immune cells, triggering an effective response to pathogens. It is also essential in the differentiation of memory T-lymphocytes, helping the body to respond rapidly when it comes into contact with a particular antigen again. It is secreted by activated T lymphocytes, NK cells and dendritic cells.
2- What is cellular immunity? and humoral immunity?
There are two types of immunity against pathogens in our organism; innate (natural) and adaptive (acquired).
The innate response is the one that is produced quickly and non-specifically. Moreover, it does not increase with exposure to the pathogen. It is a first barrier in our organism among which are: physical barriers such as the skin or mucous membranes, chemical barriers such as the pH of fluids, lipids, biochemical barriers such as enzymes or acute phase proteins and cellular barriers such as macrophages, dendritic cells or NK cells (all of which are different types of lymphocytes), among others.
The adaptive response is slower, much more specific, and does increase with exposure to the pathogen. This response is mediated by T and B lymphocytes.
Within the adaptive immune response, two types can also be differentiated:
- Humoral immunity acts against extracellular pathogens through B lymphocytes, which, upon encountering them, are transformed into antibody-producing plasma cells. Once the disease has passed, we are likely to develop memory B lymphocytes and the next time we come into contact with the virus, the response to it will be faster.
- Cell-mediated immunity is mainly specialized in fighting intracellular pathogens (such as viruses). Macrophages, NK cells and dendritic cells* come into contact with the pathogen, produce antigens and present them to other classes of T-lymphocytes, mainly cytotoxic and helper T-lymphocytes. These helper T lymphocytes are responsible for activating other immune cells by secreting cytokines and further antigens.
As the disease passes, some T lymphocytes will have differentiated into memory T lymphocytes, which, like the memory B lymphocytes, will manage a more rapid immune response the next time the pathogen is contacted.
3- What is the difference with the ELISA test?
The detection of antibodies (IgA, IgM and IgG) against SARS-CoV-2 by ELISA is used to detect humoral immunity, while the COVID Cellular Immunity Test based on the ELISPOT technique detects the presence of cytokines released by T lymphocytes, i.e. cellular immunity.
4- Which one is better, an ELISA or a Cellular Immunity Test?
Both tests are complementary, since each of them identifies a type of immune response against SARS-CoV-2.
5- Are the results reliable?
Absolutely. These tests are very specific, moreover, the cytokines released in response to an antigen can be detected at the level of a single cell through the ELISPOT technique, so it is possible to calculate the frequency of T cells capable of recognizing the pathogen and, therefore, to detect whether or not there is cellular immunity.
6- How long does it take to get the results? What does the test require?
Results are delivered on Fridays from 8:00 p.m. regardless of the day of the test. The results will be in English and Spanish.
To perform the test we will only need an intravenous blood sample (4mL) and it is advisable that the person being tested comes hydrated, being essential to have drunk water or other liquid in abundant quantity before the appointment. The latter is essential for infants and children.
It is not necessary for the person to come fasting.
7- How much does it cost and where can I have a COVID Cellular Immunity Test?
The price of the COVID Cellular Immunity Test (ELISPOT) for individuals is 199€ per person. The price of the ELISA test from Monday to Friday is €55 and the post-vaccine and post-COVID IgG ELISA is €35with a supplement of €5 more on weekends and holidays. The tests can be performed in Madrid, in our clinic at Paseo del General Martínez Campos 46.
*Macrophages, dendritic cells and NK cells, in addition to creating and presenting antigens, also synthesize cytokines that activate other T lymphocytes.