Immune cells, commonly known as white blood cells, include lymphocytes and various phagocytes, especially lymphocytes that can recognize antigens and produce specific immune responses. Lymphocytes are the basic components of the immune system and widely distributed in the body. T lymphocytes and B lymphocytes are mainly activated by antigen stimulation, and they divide, proliferate and produce specific immune responses.
In addition to T lymphocytes and B lymphocytes, there are four types of K lymphocytes and NK lymphocytes. T lymphocyte is a multifunctional cell group. In addition to lymphocytes, cells involved in immune response include plasma cells, granulocytes, mast cells, antigen presenting cells and cells of mononuclear phagocyte system.
1, t lymphocyte
Thymus-dependent lymphocytes. It can also be called T cells for short. Pluripotent stem cells from bone marrow (from yolk sac and liver in embryo). At present, it is believed that a part of pluripotent stem cells or pre-T cells in human bone marrow migrate to thymus, differentiate and mature under the induction of thymosin, and become immunocompetent T cells.
2.b lymphocytes
It can also be called b cells for short. Pluripotent stem cells from bone marrow. In birds, it develops in bursa of fabricius, so it is also called bursa-dependent lymphocyte for short)/bone marrow-dependent lymphocyte, which is differentiated from lymphoid stem cells in bone marrow. Compared with T lymphocytes, it is slightly larger.
These lymphocytes will proliferate and differentiate into a large number of plasma cells after being stimulated by antigens. Plasma cells can synthesize and secrete antibodies and circulate in the blood. B-cell lymphoma is the most common lymphoblastic leukemia, and the research on this disease is constantly emerging.
3.k lymphocytes
Antibody-dependent lymphocytes, also known as antibody-dependent lymphocytes, are directly derived from bone marrow pluripotent stem cells. There is no antigen mark on their surface, but there is an antibody IgG receptor. In order to kill target cells, there must be corresponding antibodies to target cells. The surface antigen of the target cell binds to the corresponding antibody, and then binds to the corresponding receptor of K cell, thus triggering the killing effect of K cell.
4.NK lymphocytes
NK cells (natural killer cells) are the third kind of lymphocytes besides T cells and B cells. The number of NK cells is relatively small, accounting for about 15% of the total number of lymphocytes in peripheral blood, and about 3%~4% in spleen. NK cells can also appear in lung, liver and intestinal mucosa, but are rare in thymus, lymph nodes and thoracic duct.
NK cells are large in size and contain cytoplasmic granules, so they are called large granular lymphocytes. NK cells can kill target cells directly, without specificity, and this natural killing activity does not require antigen sensitization in advance, nor does it require antibody participation, and there is no MHC limitation.
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Principle and mechanism of immune cells
Like humoral immunity, cellular immunity can be divided into three stages: induction, reaction and effect. Its mechanism includes two aspects: (1) the direct killing effect of sensitized T cells. When sensitized T cells come into contact with the target cells with corresponding antigens again, specific binding will occur, thus stimulating and changing the permeability of the target cell membrane.
The osmotic pressure in the target cells changes, and the target cells swell and dissolve, leading to death. Sensitized T cells are not harmed in the process of killing target cells, and can attack other target cells again. Involved
This sensitized T cell is called killer T cell. ⑵ Kill the target cells through the synergistic effect of lymphatic factor. For example, skin response factors can increase the permeability of blood vessels, making it easy for phagocytes to swim out of blood vessels.
Macrophage chemokines can attract corresponding immune cells to concentrate on the site where antigens are located, which is beneficial to phagocytosis, killing and elimination of antigens. Due to the synergistic effect of various lymphatic factor, the immune effect is expanded, and the aim of removing antigen foreign bodies is achieved.
In anti-infection immunity, cellular immunity mainly participates in the immune response to intracellular parasitic pathogenic microorganisms and tumor cells, the formation of delayed allergic reaction and autoimmune diseases, and the regulation of transplant rejection and humoral immunity. It can also be said that in anti-infection immunity, cellular immunity is not only the main force of anti-infection immunity, but also participates in immune protection; It is also an important factor leading to immunopathology.
T cells are the main cells of cellular immunity. Its immune sources are generally: parasitic protozoa, fungi and foreign cell clusters (for example, transplanted organs or their own cells are infected by viruses). Cellular immunity also has memory function.
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