Blood & Laboratory Values

B Lymphocytes – Function & Diseases

B lymphocytes

B lymphocytes ( B cells ) belong to the group of white blood cells ( leukocytes ) and are the only cells that can also form antibodies . If they are activated by foreign antigens , they differentiate into memory cells or plasma cells .

What are B lymphocytes?

B lymphocytes are assigned to the group of white blood cells. Their most important task is the formation of antibodies .

The lymphocyte type was discovered for the first time in birds; in humans, B cells are formed in the bone marrow or in the fetal liver . B lymphocytes make up about five to ten percent of the lymphocytes circulating in the blood . They are mainly found in the bone marrow , the lymph nodes , the spleen and in the lymph follicles.

Function, effect & tasks

The human immune system can be divided into three parts:

The adaptive defenses include the T-lymphocytes and B-lymphocytes, whereby these defense mechanisms can be divided into cell-mediated and humoral immunity. B lymphocytes play an essential role in the immune system. The term B cell comes from the English term “bone marrow”, which means something like bone marrow. If there is contact with an exogenous pathogen, so-called immune globulins are formed in the B lymphocytes.

An antibody is produced against each antigen, with the B lymphocytes concentrating primarily on toxins and bacteria. Antibodies are special proteins that can be found in various body fluids. Antibodies protect the body from:

  • viruses
  • bacteria , fungi
  • Foreign and tumor tissue
  • animal poisons
  • bee pollen
  • artificial and natural substances

If the B lymphocytes divide, plasma cells are formed. Some of them only exist for a few weeks, others belong to the memory cells and remain in the human body for years. These are also called memory B cells.

In addition, the B lymphocytes are also divided into plasma blasts and naïve B cells based on their function. Plasmablasts are activated B-lymphocytes, whereas non-activated B-cells can be found in the lymphatic system or in the bloodstream . If they perceive an antigen, it is taken up and subsequently released as a protein complex.

Formation, Occurrence, Properties & Optimal Values

First, a mature B lymphocyte circulates in the bloodstream and in the lymphatic system. When it comes into contact with an antigen, it binds to the B cell receptor. This process is called receptor-mediated endocytosis. The antigens can thus reach the acidic cell compartments, where they are split into peptides. It is then transported to the cell surface.

However, binding alone is not sufficient to activate the B lymphocyte. The B lymphocyte can only be activated and antibodies formed if the antigen is also recognized as foreign by a T helper cell. Basically, B cells need two signals for activation. They receive the first via the binding of the receptor, the second via the binding of CD4oL to CD40. After activation, the B lymphocyte travels to the nearest lymph node , where it differentiates into plasma cells.

These then form antibodies. Plasma cells are oval to spherical in shape, their nucleus is usually eccentric, and they are highly basophilic. Mature plasma cells are found in the spleen, bone marrow , lymph node marrow, exocrine glands, mucous membranes, and chronic inflammatory sites.

A smaller proportion develops into B memory cells, which circulate in the lymphatic system or in the blood even after an infection has been fought off. If an antigen then gets back into the body, the immune reaction occurs faster because the blueprint for the corresponding antibodies is already known. The information about the structure of the antibodies can be found in the DNA of the B lymphocytes. Since the human body comes into contact with billions of different antigens, there are also a wide variety of lymphocyte clones that have different DNA codes.

In addition to the different end and maturation stages of B lymphocytes, there are basically two types of B cells: B2 cells are referred to as “ordinary” B cells, while B1 cells are larger and are mainly found in the abdominal cavity . These cells are not present in the peripheral lymph nodes. In addition, they differ from the B2 cells by certain surface markers.

Diseases & Disorders

An increase in B lymphocytes can be detected in the following diseases:

 

Reduced values, on the other hand, occur in the following diseases:

In B-cell lymphoma, there is a multiplication of a group of lymphocytes at one point in the body, which is also known as clonal growth. It is possible that the disease is limited to lymphatic tissue, but the lymphocytes can also enter the blood , in which case it is referred to as a so-called lymphatic leukemia. There are two groups of lymphomas:

Non-Hodgkin’s lymphoma can in turn be subdivided into B-cell NHL and T-cell NHL. Examples of B-cell lymphomas include:

  • immune cytomas
  • multiple myeloma
  • chronic lymphocytic leukemia

Chronic lymphocytic leukemia occurs very frequently, with the following symptoms:

  • general weakness
  • rashes, itching
  • swelling of the lymph nodes
  • Enlargement of the liver and spleen
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Hello! I am Lisa Newlon, and I am a medical writer and researcher with over 10 years of experience in the healthcare industry. I have a Master’s degree in Medicine, and my deep understanding of medical terminology, practices, and procedures has made me a trusted source of information in the medical world.