The immune system, made up of cells, proteins, tissues and organs, defends us on a daily basis from the complex of the human species and other living beings against germs and microorganisms. While the skin, saliva and mucous membranes are the main biological barriers in the body, the immune system encompasses secondary and tertiary defense.
Our body is not an airtight compartment, because the respiratory tract and the mouth, for example, are ideal conduits for the entry of pathogens into our body. Beyond the skin and mucous membranes, there must therefore be a complex defense system that protects us once the germ is already in us.
To give you an idea, about 20% of the world’s population has the flu as of the time of this reading. This fact highlights that, of course, our immune system fights pathogens at virtually every moment of our lives. Lymphoblasts are the precursors of lymphocytes, the immune cells par excellence. If you want to know all about them, keep reading.
What is a lymphoblast?
According to the National Cancer Institute (NIH), a lymphoblast is defined as an immature cell that serves as a precursor to lymphocytes, the cell bodies responsible for tertiary immune barriers.
However, at first we find a clear terminological conflict, as a lymphoblast also refers to a lymphocyte that has enlarged after being stimulated by an antigen. The two events are completely different, but the same word is used to refer to them. We will dissect each of them in detail in the following lines.
1. Lymphoblast as a precursor
Under normal circumstances, lymphoblasts (believed to be the cells that give rise to lymphocytes) they are found in the bone marrow of the long bones of healthy people. If one takes the meaning of the term “lymphoblast” as a progenitor, it could be interchangeable with that of “common lymphocyte progenitor”, since both give rise to the prolymphocyte, an intermediate form which ultimately results in the desired lular cell type.
In general, we can describe the transformation of lymphoblast into functional lymphocyte in the following steps:
- Maturation of lymphoblasts or common lymphocyte progenitors in the bone marrow results in involvement in B or T cell lines.
- Immature lymphocytes proliferate at various stages of maturation. For example, proliferation of prolymphocytes occurs to ensure the provision of an adequate number of cells which mature later.
- The lymphocytes are selected in several stages during their maturation in order to retain the specificities useful at each occasion.
Without wishing to enter into too complex terminology, we will say that this last step refers to the fact that the selection of one lymphocyte or another is based on the expression of intact components of the receptor by the antigen and what they recognize.
At the end of this whole process, lymphocytes have receptors for specific antigens, which allows them to produce antibodies. and therefore for the destruction of abnormal cells (ideally germs and other pathogens). These cell bodies make up 30% of total peripheral blood leukocytes and, as we have said, represent tertiary immune barriers.
T cells act directly on and destroy the pathogen, while B cells detect antigen (a foreign substance, presumably produced by a pathogen) and generate specific antibodies for it. When an antibody binds to its antigen, the invading microorganism loses its pathogenicity. As you can imagine, this whole process is much more complex than the one described here, but we just need to show a general picture of it.
2. The lymphoblast in the form of a lymphocyte with altered morphology
On the other side of the coin, and confusing as it sounds, a lymphocyte that has enlarged after being stimulated by an antigen is also called a lymphoblast.. In this case, upon recognition of the antigen, this type of white blood cell is activated, causing growth at cytoplasmic, nuclear and messenger RNA levels and at certain protein levels.
Thus, the large lymphoblast begins to divide 2-4 times every 24 hours for 3-4 days, resulting in 1000 clones of the original lymphocyte, each of the clones exhibiting specificity for the same antigen when it has it. activated first. Finally, the resulting cells can be differentiated into specific cell types that will somehow fight against the pathogen.
Characteristics of a lymphoblast
We have already shown you what a lymphoblast is, but to give us a general idea of this particular cell body, we still have describe it at the morphological level. Here are some of the most relevant facts about their physiology:
- The lymphoblast ranges from 10 to 18 micrometers in size.
- Its shape is rounded and oval.
- It has a single cell nucleus and a bluish cytoplasm with granulations.
- The nucleus-cytoplasm ratio ranges from 5: 1 to 7: 1.
- It also usually has between 1 and 2 nucleoli, regions of the cell nucleus that take care of the production and assembly of ribosomes in cells.
Acute lymphoblastic leukemia
Leukemias are cancers that occur in cells that would normally differentiate into different types of blood cells, in this case B and T lymphocytes.. When an uncontrolled proliferation of lymphoblasts occurs (again, if one conceives of lymphoblasts as a precursor of a lymphocyte), they invade the bone marrow preventing the production of other cells, such as red blood cells and platelets. . This condition is known as Acute Lymphoblastic Leukemia (ALL) and is very dangerous to health.
This pathology does not know gender, ethnicity or age, although it is very rare to present it, the foundations estimate that its prevalence is 1.29 patients per 100,000 inhabitants. Although it is a very rare disease, ALL is the most common type of cancer in children under the age of 20 (almost 60% of leukemias occur in this age group).
Acute lymphoblastic leukemia is caused by a mutation of a single lymphoblast in the bone marrow that triggers the reaction described aboveBut researchers around the world have yet to find out what actually leads to this event. According to the Spanish Association of People Affected by Lymphoma, Myeloma and Leukemia (AEAL), here are some of the risk factors that can promote ALL disease:
- Genetic factors, that is, individual chromosomal alterations determined from the moment of the patient’s birth.
- Being exposed to x-rays or ionizing radiation before or after birth.
- Have had treatment based on chemotherapy.
- Infections with certain types of viruses (especially certain types of retroviruses).
- Come in contact with certain chemicals, such as benzene and certain alkylating compounds.
It is not all bad news at first glance, because the survival rate of patients with acute lymphoblastic leukemia 5 years after diagnosis under 20 years is 90%. Unfortunately, if we analyze data from patients over the age of 20, the 5-year survival rate after diagnosis does not reach 40%. All these data are only estimated figures, since each case depends on the physiological characteristics of the individual and his course of the disease.
A terminological confusion
As reported by the Chronic Lymphoblastic Leukemia Research Consortium, 1 lymphoblast is defined as “a lymphocyte that has grown in size after being stimulated by an antigen. Lymphoblasts look like immature lymphocytes, and were once thought to be cells. precursors “. So where do we stand? Multiple sources bibliographies use the term lymphoblast as a precursor, which transforms into a prolymphocyte and this will give rise to the known B and T lymphocytes responsible for the immune response.
On the other hand, by other sources such as the one just cited 1, the lymphoblast is a stimulated lymphocyte, not a precursor. Of course, spaces like this point out that, in certain specific cases, the medical terminology of a particular event does not have to be the same in all the sources consulted.
- What is Acute Lymphoblastic Leukemia ?, Spanish Association of People Affected by Lymphoma, Myeloma and Leukemia. Collected December 13 at http://www.aeal.es/leukemia-linfoblastica-aguda-espana/2-que-es-la-leucemia-linfoblastica-aguda/
- ATLAS OF HEMATOLOGY, collected December 13 at http://www.qualitat.cc/sitebuildercontent/sitebuilderfiles/atlas.hematologia.pdf
- Definition of lymphoblast, National Cancer Institute (NIH). Retrieved December 13, from https://www.cancer.gov/espanol/publicaciones/diccionario/def/linfoblasto
- Lymphoblast Free Dictionary. Retrieved December 13, from https://es.thefreedictionary.com/linfoblastos
- Immune System, Radyschildren.org. Retrieved December 13, from https://www.rchsd.org/health-articles/sistema-inmunolgico-3/#:~:text=El%20sistema%20inmunol%C3%B3gico%20es%20la,el%20cuerpo% 20y % 20causes% 20 diseases.
- Vásquez Palau, G., Ramírez Castro, JL, Posada Díaz, A., Serra, M., Botero, OL, Durango, NE, … and Tabares, JG (2002). Acute lymphoid leukemia: cytogenetic study in children treated at the Sant Vicenç de Paül University Hospital in Medellín during the period 1998-2001. Iatreia, 15 (4), 217-225.