Origin of lymphocytes: the body's resistance to infection

2021-05-08 12:50 AM

For each last formed T or B function, the genetic makeup codes indicate only one specific antigen. The adult cells then become highly specific T and B cells that multiply and spread to the end of the lymphoid tissue.

There are only a few hundred to a few thousand genes for millions of types of antibodies and T lymphocytes. First, it remains a mystery, how few genes could code for millions of antibodies or solid T cells. Different signals are produced by lymphoid tissue. Mystery has been discovered.

The entire Te gene that forms each type of T or B cell was never in the original stem cells where immune function cells were formed. Instead, it's just "genome" - there are actually hundreds of them, but not the entire genome. During the pre-processing T and B lymphocytes - corresponding to the gene segments, become random mixes of each other, eventually forming entire genes in this way.

Figure. An antigen only activates lymphocytes that have additional receptors on the cell surface and recognize a specific antigen. Millions of different lymphocyte lines exist (shown as B1, B2, and B3). When the lymphocyte line (B2 in this example) is activated by its antigens, it reproduces to form a large number of cloned lymphocytes, which then secrete antibodies.

Since there are several hundred types of gene fragments as well as millions of different combinations in which fragments can be arranged in single cells, it is understandable that millions of different types of cell genes could occur. For each last formed T or B function, the genetic makeup codes indicate only one specific antigen. The adult cells then become highly specific T and B cells that multiply and spread to the end of the lymphoid tissue.

Mechanism of activating Lymphocytes

Each copy of the lymphocytes is responsive to only one antigen (or several similar antigens with almost exactly the same stereochemistry). The reasons for this are as follows: In the case of B-lymphocytes, each cell with approximately 100,000 antibody molecules will react highly specifically with only one antigen. Therefore, when the appropriate antigen arrives, it immediately attaches to the antibody to the cell membrane; This leads to the activation process, which is described in more detail afterwards. In the case of T lymphocytes, antibody-like molecules, called surface receptor proteins (or T-markers), are on the surface of the T-cell membrane, and these are also assessed for characterization. high signal like specific antigen activator.

The role of macrophages inactivation

Besides the lymphocytes in the lymphoid tissues, millions of macrophages are also present in the same tissue. These macrophages line the sinuses of the lymph nodes, spleen, and other lymphatic tissue, and they are clustered by lymphocytes in the lymph nodes.

Most invasive organisms are first phagocytic and ingested by the macrophages and antigen products released into the cytoplasm of the macrophage. This macrophage then overcomes the antigens that are directly related to the lymphocytes, thereby leading to the activation of specific lymphoid clones. In addition, the macrophage secretes a special activator, interleukin-1, that promotes the growth and reproduction of more specific lymphocytes.

The role of T cells in Lymphoid B activation

Most antigens activate both T and B lymphocytes at the same time. Some formed T cells, called T-helper cells, secrete specific substances (collectively called lymphokines), which activate B lymphocyte-specific cells. -helper, the number of antibodies formed by B-lymphocytes is usually small. We will discuss the cooperative relationship between T-helper cells and B cells after describing the mechanisms of the T-cell systems of the immune system.

 

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