Immune Cells Count!

Lymphocytes are white blood cells that are divided into two groups, the B lymphocytes and the T lymphocytes. The B lymphocytes are particularly responsible for the production of antibodies. The T lymphocytes can kill infected body cells directly as well as support the B lymphocytes. Both groups of lymphocytes can form memory cells to enable an appropriate defense response quickly in the event of renewed contact with the pathogen.

The T cells (CD3+ lymphocytes) are a subgroup of the lymphocytes, which in turn form a subgroup of the white blood cells (leukocytes). T cells comprise about 70 percent of the lymphocytes in the blood. The special feature of these cells is that they carry the so-called CD3 antigen on their cell surface.

The T cells fulfill their function within the framework of the so-called cellular immune system.
T cells play an important role in the following pathological processes:

• Defense against infections with viruses, fungi and certain bacteria (e.g. tuberculosis bacteria).
• Defense against tumor cells
• Certain allergic reactions (of the delayed type)
• Rejection reactions of transplants (e.g. rejection of a donor kidney)

The T cells themselves can in turn be divided into a number of further subgroups:

T helper cells (CD3 and CD4 positive),
T suppressor cells (CD3 and CD8 positive),
"NK-like" T cells (CD3, CD16 and CD56 positive),
activated T cells (CD3 and HLA-DR positive).

Source and further information here.

The T-helper cells (CD4 lymphocytes) are a subgroup of the T-lymphocytes, which in turn are a subgroup of the white blood cells (leukocytes).
Overall, T cells comprise about 70 percent of the lymphocytes in the blood and T helper cells about 30 percent.

The determination of T-helper cells, T-suppressor cells and the ratio of the two to each other (the so-called CD4/CD8 ratio) in HIV infection and AIDS (Acquired Immune Deficiency Syndrome) has a high diagnostic value.
In this context, leukocyte typing is used to determine the so-called immune status. The background to this diagnostic procedure is the fact that the HI virus attacks and destroys the T helper cells in particular.

Source and further information here.

The T suppressor cells (CD8 lymphocytes) are a subgroup of the T lymphocytes, which in turn form a subgroup of the white blood cells (leukocytes).
Overall, T cells comprise about 70 percent of the lymphocytes in the blood and T suppressor cells about 30 percent.

The determination of T helper cells, T suppressor cells and the ratio of the two to each other (the so-called CD4/CD8 ratio) is of great diagnostic value.

Source and further information here.

B cells (CD19+ lymphocytes) are a subset of lymphocytes, which in turn form a subset of white blood cells (leukocytes).

B cells comprise about 15 percent of the lymphocytes in the blood. 

In humans, B cells are formed in early childhood in the liver and in the bone marrow. In the course of further development, the B cells finally settle in the lymphatic tissue:

• Lymph nodes
• Spleen
• Tonsils
• lymphoid tissue of the mucous membranes (so-called MALT - Mucosa Associated Lymphoid Tissue)
• Bone marrow etc.

The B cells fulfill their function within the framework of the so-called humoral immune system.

This means that certain substances produced by the B cells perform the specific tasks within the immune system. These substances are called antibodies.

When pathogens (e.g. bacteria, fungi, viruses) enter the body, B cells are stimulated and subsequently transformed into plasma cells. These plasma cells finally produce the antibodies and release them into the tissue as well as into the blood.

Source and further information here.

The NK cells are a special subgroup of the lymphocytes, which in turn form a subgroup of the white blood cells (Leukocytes).

The NK cells comprise about 15 percent of the lymphocytes in the blood. The special feature of these cells is that they carry the antigens (these are special protein structures) CD16 and CD56 on their cell surface.
The NK cells fulfill their function within the framework of the so-called cellular immune system.

NK cells play an important role in the direct destruction of diseased body cells (e.g. virus-infected cells, tumor cells). On the one hand, NK cells can recognize such diseased cells themselves. On the other hand, NK cells also recognize cells that are loaded with antibodies, for example.

NK cells play an important role in the following pathological processes:

• Defense against infections with viruses, fungi and certain bacteria (e.g. tuberculosis bacteria),
• Defense against tumor cells.

Source and further iInformation here.

Regulatory T cells (Treg) are a specialized subset of T lymphocytes and regulate the self-tolerance of the immune system.

Regulatory T cells suppress the activation of the immune system in certain situations. Thus, they regulate its self-tolerance and reduce the risk of developing autoimmune diseases and allergies. They also prevent organ rejection after transplantation and fetal rejection by the mother.

Source and further information here.

Neutrophil granulocytes are a subtype of white blood cells (leukocytes). They make up about two-thirds of all leukocytes. Neutrophils are part of the cellular immune system and fight pathogens. 

Neutrophil granulocytes are an important part of the innate immune system. When foreign bodies or pathogens enter the body, substances are released that attract the neutrophils. These then leave the bloodstream and enter the tissues. There they take on their task as scavenger cells, so-called phagocytes: they absorb pathogens and destroy them.

In addition, neutrophil granulocytes clear up destroyed tissue cells. In the process, pus is formed from them and the destroyed tissue cells.

Source and further information here.

Monocytes are a subtype of leukocytes, i.e. white blood cells. They make up about four to ten percent of all leukocytes and are an important part of the innate immune system.

They are formed in the bone marrow, then remain in the bloodstream for two to three days before finally invading tissue, for example liver or connective tissue. There they grow five to tenfold and develop further into so-called macrophages. These are "scavenger cells." This means that they absorb invading pathogens. Inside them, the macrophages have various substances and enzymes to kill and break down the pathogen.

However, macrophages do not only degrade pathogens, but also old endogenous material, for example in the context of bone metabolism. In addition, macrophages and their precursor, monocytes, play an important role in the activation of the acquired immune system.

Source and further information here.