Leukocytes: what are they, types and functions in the human body?

An overview of the main types and functions of white Blood cells, or leukocytes.

From a clinical point of view, knowledge of the various components of blood and their concentrations is of essential importance. From red blood cells to leukocytes, platelets or hemoglobin, every substance carried in blood has an essential function for the organism.

In addition, the knowledge of leukocytes at the evolutionary level should not be underestimated. The immune system of living beings allows us to develop in space and time over the years, for if we did not have such effective methods of defense against pathogens, our existence would be much shorter and more difficult.

For all these reasons, we find it of special interest to dive into the world of leukocytes.. Inside our body we have a veritable legion of protectors, and today we tell you all about each of them.

Leukocytes: protective cells of life.

From a terminological point of view, a leukocyte, or white blood cell, is defined as a type of blood cell (blood cell) that is produced in the bone marrow and found in the blood and lymphoid tissue.. These cell bodies form the human immune system along with many other barriers (such as mucous membranes or skin, for example), and as a whole, they seek the permanence of the individual over time for as long as possible.

Without further ado, and since we have a lot of work to do, here are the types of leukocytes and their characteristics.

1. Granulocytes

They are the most frequent type of white blood cell in the blood.representing 70-75% of this protective cellular conglomerate. Depending on the type of staining that allows their identification in the patient's blood sample, we can differentiate between different types of granulocytes.

1.1 Neutrophils

Within the granulocyte group, neutrophils are the most common cells, accounting for 60-70% of leukocytes. account for 60-70% of the leukocytes in humans.. As morphological characteristics, they measure 9 to 12 micrometers and the granules of their cytoplasm are stained light purple with neutral dyes (hence their name).

They mature in the bone marrow and are stored there before being sent into the bloodstream, a process that takes a total of 10 days. After this, they travel through the blood vessels and through small pores (diapedesis) are able to enter tissues affected by pathogens. These agents remain in blood for about 8-20 hours, but their half-life is increased by several magnitudes when they enter infected or inflamed tissues.

Neutrophils kill 3 to 20 bacteria in their lifetime.. Attracted by toxic compounds synthesized by the pathogen, these white blood cells kill the threat by phagocytosis and release of hydrolytic enzymes. In addition to this, they also promote the local inflammatory process typical of an infection.

1.2 Basophils

On the other side of the coin are the basophils, which are the least common white blood cells. are the least common white blood cells, accounting for 0.5-1% of the total number of white blood cells.. They are also more "ethereal" than their previously described peers, as they mature in the bone marrow in a total of three days and their permanence in the blood is a few hours. They measure about 12-15 micrometers (they are the largest leukocytes), have a bilobed nucleus and stain with basic dyes.

These agents have an active immune response, as they have specific granules that release histamine, hepatitis B and hepatitis C.They have specific granules that release histamine, heparin, bradykinin, serotonin and other compounds that mediate inflammatory responses. They are an essential cell body in allergic responses.

1.3 Eosinophils

The last within the granulocyte group, but no less important. Eosinophils occur in a proportion of 2-4% of the total white blood cells. Their size is similar to that of a neutrophil, and they are stained orange by acid dyes (eosin).

Although they have a half-life in blood of 3 to 4 days, the highest concentration of eosinophils is found within the tissues of the body.It has been found that there are 100 tissue eosinophils for every one circulating eosinophil. Their main function is the detection and phagocytosis of larvae and parasites, as well as the modulation of the allergic response, as they prevent the exacerbation of the same by synthesizing substances that counteract basophils.

2. Agranulocytes

On the other hand, we have the agranulocytes, which, as their name suggests, are cells lacking cells lacking granules of a mononuclear nature.. We mention briefly the two types within this group.

2.1 Lymphocytes

Of course, no summary paragraph can do justice to the complexity and functionality of these cell bodies. Lymphocytes are more common in the lymphatic system than in the blood plasma and can be divided into two types. and can be divided into two types according to their origin and functionality: B- and T-lymphocytes.

Although we may err on the side of reductionism, we can summarize the general function of lymphocytes in the following concept: B lymphocytes would be the "body's recognition system", since they unequivocally detect pathogens and immobilize them. On the other hand, T lymphocytes are the "manpower", since their lytic activity neutralizes the pathogenicity of cells infected by microorganisms.

2.2 Monocytes

The last stop on this journey is the monocytes, the leukocytes. monocytes, the largest leukocytes (18 micrometers) which represent 2-8 % of the white blood cells in the blood.. Their formation process in the bone marrow takes two to three days, but they do not remain in the blood for more than 36 hours, as they migrate rapidly to infected tissues.

Their function is basic: they phagocytize pathogens, i.e. they literally eat them.. It is estimated that a monocyte can ingest up to 100 bacteria in its lifetime, so they are considered the white blood cells with the highest bactericidal capacity in the whole list.

Functions of white blood cells

Without realizing it, in the above classification we have described all the essential functions of leukocytes. However, a general review never hurts. As mentioned above, white blood cells are responsible for promoting inflammatory responses. are responsible for promoting inflammatory responses, phagocytizing pathogens and recognizing and isolating them, among many other functions..

All this is part of both the innate and acquired immune response, an excellent defense mechanism that allows us to thrive in an environment full of potentially harmful microorganisms.

Problems in the defense barriers

What happens when these essential cells fail? The leukocyte formula is a type of medical analysis that allows us to measure the concentration of white blood cells in the blood, and depending on the mismatches observed, various pathologies can be recorded.Depending on the observed mismatches, various pathologies can be recorded. Among them we find the following:

• Neutropenia: a number of disorders can promote the decrease of white blood cells in blood. In this case, the most affected are usually the neutrophils.
• Lymphocytopenia: This is defined as a total lymphocyte count of less than 1.0x109/L. Factors such as radiation or chemotherapy may promote this condition.
• Neutrophilia: An excess of neutrophils in the circulating blood. It can be caused by anything from infections to serious diseases such as leukemia.
• Eosinophilia: when the presence of eosinophils is greater than 0.65×109/L. It is usually caused by infectious processes.

It should be noted that it is not a disease in itself, but rather a sign of an underlying problem.. Sporadic events of neutrophilia, for example, are relatively normal, because in the presence of an inflammatory process or infection, it is natural for these cells to proliferate to a greater extent.

Of course, abnormal leukocyte values may be due to a number of pathologies. can respond to a number of very different pathologiesFrom infections to genetic diseases, bone marrow disorders, cancerous processes, surgeries and many other events, a sustained erroneous white blood cell count should set alarm bells ringing.

Summary

As we have seen, leukocytes come in various shapes, sizes and stains. In addition to this, each of them performs a unique and irreplaceable function as far as the immune system is concerned. From inflammation to phagocytosis, these cellular agents fight tooth and nail against pathogens that enter our body.

Of course, it is impressive to know that such an effective and refined defense system is capable of developing within our body. The key to evolution lies in refinement and applies far beyond the immune system, and therefore, we will never cease to be amazed when describing and discovering processes such as these.

Bibliographical references:

• Abbas, A. K., Lichtman, A. H., & Pillai, S. (2015). Cellular and molecular immunology. Elsevier.
• Arevalo, M., Arredondo, S., Walter, T., & Heresi, G. (1986). Techniques to evaluate the phagocytic, opsonic and bactericidal capacity of polymorphonuclear leukocytes. Rev. chil. tecnol. méd, 383 - 388.
• White blood cell definition, cancer.gov. Retrieved Oct. 16 from https://www.cancer.gov/espanol/publicaciones/diccionario/def/leucocito.
• Leukocyte formula, Medlineplus.gov. Retrieved October 16 from https://medlineplus.gov/spanish/pruebas-de-laboratorio/formula-leucocitaria/.
• Topic 23: white blood cells. Effervescent.com. Retrieved October 16 from http://www.enfervescente.com/privado/wp-content/uploads/2013/02/Tema-23.-Gl%C3%B3bulos-blancos-o-leucocitos.pdf.