Definition
Lymphocytes are a highly specialized subgroup of leukocytes, the white blood cells that belong to the immune system, the body’s own defense system. Their name is derived from the lymphatic system, as they are particularly common there. Their main task is primarily to defend the body against pathogens such as viruses or bacteria.
For this purpose, certain cells specialize in only one pathogen at a time, which is why they are also called the specific or adaptive immune system. But they also help to eliminate mutated body cells, so-called tumor cells, which can lead to cancer. A distinction is made between B and T lymphocytes, as well as natural killer cells, each with different functions.
Function of lymphocytes
When a pathogen enters the body, it is first taken up and broken down by unspecific defense cells, such as macrophages (“giant eating cells”). The macrophages in turn display fragments of the pathogen, so-called antigens, on their surface and thus activate T-helper cells, which serve as mediators between the different specific immune cells, the lymphocytes. The lymphocytes ensure that the immune system is highly adaptable and can react in a finely regulated manner to different threats.
The humoral (= body fluids) immune response is based on antibodies, a specific form of proteins, which are produced and secreted by plasma cells. It is mainly designed for pathogens that can multiply independently, e.g. bacteria, but also other unicellular organisms. Antibodies can, for example, attach themselves to the surface of bacteria and clump them together due to their special shape (agglutination).
This in turn makes it easier for unspecific immune cells to find and eliminate the pathogens. Antibodies can also perform a number of other functions (see B lymphocytes). The cellular immune response is mainly specialized on viruses, but also on certain bacteria, which cannot live independently and therefore have to attack body cells.
If a cell is attacked, it can show fragments of the parasite on special receptors on its surface. T-killer cells destroy the attacked cells and thus prevent the further spread of the pathogen. as well as T-lymphocytes
