2013-03-17 23:33:21
Some bacteria live inside our cells
As we know, the immune system is essential for our health, protecting us from the attack of viruses, bacteria, fungi, worms and other parasites. In recent decades, much has been learned about the functioning of this crucial system, which has allowed, among other things, to develop effective vaccines against a number of diseases, which have saved millions of lives. Likewise, manipulation of the immune system by pharmacological means makes the success of organ transplants possible since, without this manipulation, all transplanted organs would be rejected, with very few exceptions.
Research on stem cells with the intention of regenerating damaged organs aims to replace them with our own cells, so that rejection does not occur and the use of immunosuppressive drugs is not necessary, which can always cause us problems, since they also make us more susceptible to infections.
However, despite all the advances made, the immune system still keeps important secrets that, little by little, are revealed by scientific research. One of them has recently been, and what we have learned by revealing it is surprising and may be very useful.
MAIT LYMPHOCYTES
A fundamental class of immune cells is made up of blood lymphocytes, of which there are two main types: B lymphocytes and T lymphocytes. B lymphocytes are responsible for the production of antibodies and their secretion into the blood, while T cells, by far the most numerous, are responsible for assisting B lymphocytes in their functions and also for detecting cells that have been infected or encountered a foreign substance. Likewise, T lymphocytes are responsible for rejection reactions to a transplant.
However, until today, it was unknown how no less than 10% of T lymphocytes, which belong, it is true, to a somewhat particular class of lymphocytes, performed their function. These particular lymphocytes, discovered only in 2003, are very numerous in the intestine, lung and liver, and because they are associated with mucosal tissues, they are called MAIT lymphocytes, for their acronym in English.
An interesting curiosity about these lymphocytes is that they are only produced in the case of having intestinal flora. Laboratory animals raised in conditions of total absence of bacteria and, therefore, lacking intestinal flora, do not develop MAIT lymphocytes. This observation already indicated that MAIT lymphocytes probably had something to do with fighting bacteria.
In 2010, it was indeed discovered that MAIT lymphocytes detected cells infected by bacteria. Some bacteria are capable of living inside our cells, at least some of them. To combat them, it is not enough to generate antibodies, since they cannot penetrate inside the cells and neutralize the bacteria. It is necessary to detect the infected cell and kill it with the bacteria it keeps inside. Only in this way can the infection be kept at bay and finally eliminated.
VITAMINED SURPRISE
But to detect a cell infected by a bacteria, it is necessary to be able to differentiate it from those that are not infected. In other words, it is necessary to detect some characteristic that distinguishes it from the others. This characteristic, in the world of cells, can only come from some molecule typical of infected cells, but not found in healthy cells. This molecule, necessarily coming from bacteria, must be able to be captured by some cellular molecule and be presented on the surface of the infected cells so that the lymphocytes can detect it. What molecule could it be? This was the mystery that until now had kept immunologists in check.
To find out, a large group of researchers from several Australian universities decided to study, using physical-chemical methods, the properties of the molecule responsible for capturing bacterial molecules and presenting them on the surface of cells to MAIT lymphocytes. They thus tried to find out what kinds of bacterial molecules had been able to capture these cellular molecules.
What their studies, published in the journal Nature, have found and demonstrated is surprising. The bacterial molecules captured and presented on the surface of infected cells are neither proteins, nor lipids, nor sugars. These are nothing less than class B vitamins, or their derivatives, synthesized by bacteria and which are necessary for their growth and reproduction. These vitamin molecules are not found on the surface of healthy cells.
There is still much to learn about the function of MAIT lymphocytes and why their development is dependent on the intestinal flora. However, this discovery opens the door to new strategies for the development of effective vaccines, which may require not only dead bacteria or their components to stimulate the immune system and induce protection, but also the vitamins that live bacteria produce and Without which the stimulation of the immune system may be defective and ineffective. Hopefully future research will achieve this goal.
WORKS BY JORGE LABORDA.
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