Innate Immunity, Acquired Immunity, Natural killer (NK) cells, Cytotoxic T-cells and T-Helper cells (TH) Explained
Innate immunity is refered to as Natural or Native Immunity which are first defenses against pathogens and foreign bodies in the body where the body's antibody binds to antigen and destroys the antigens. it is the cell's natural way of defensing the body by recognizing the structural features of the pathogen such as lipopolisacharide feature in gram negative bacteria. This immunity is non-specific, it attack all types of pathogens equally. Innate immunity can be divided into first line of defence and second line of defence. The first line of defence includes the Skin and the Mucus membrane which prevents pathogen from getting into the body. The second line of defence is triggered when the first line of defence fails. The Second line of defence include phagocytes, Natural Killer Cells, and Antimicrobial substances, and they help to destroy the antigens that get into the body. Adaptive immunity on the other hand are aquired immunity, and they are specific in their immunity having memory cells to identify the antigen the next time there is a re-entry. Let's quickly discuss the immune cells in the body.
Natural killer (NK) cells, maybe you have heard about it are non-pathogenic cells that are pathogenic. They do not cause harm to normal body tissues but they would attack and damage external tissue cells that invade the body. These external cells cause infections, and so they are to be attacked. These cells are important in the defense mechanism of the body, preventing it from harmful infections. This group of cells is regarded as the group-1 Innate lymphocyte cells as they recognize external materials and pathogens very quickly and they interact against intracellular pathogens which are inside the host cells such as the macrophages through Direct Response, and extracellular pathogens which are not inside the cell through indirect response. Natural Killer (NK) cell are matured in the Bone marrow, Spleen, Lymph nodes, and in the Thymus.
Compared to Cytotoxic T-cells, Natural killer (NK) cells is a complex. Cytotoxic T-cells are called killer T-cells because they kill cancer cells by releasing CT cell receptors which binds with the antigen that is in the body, after which cytotoxins are released to combat the antigens. Cytotoxins such as Perforins and Granzymes are released causing to the cells to die. With the Natural Killer cells, when a virus attacks the normal cell in the body, they get into the cytoplasm of the cell infecting the cell and allowing the cell to possess altered protein and release Type-1 interferrons that causes the trigger of the Natural Killer Cells to become Effector Natural Killer Cells which goes to the cells and binds to the altered protein with its specific receptor after which granules known as Cytokines (Iterleukins 2, 15, and 8) will be released which will attack the infected cell. Perforins break the cell membrane of the infected cells. Just as the name implies, perforation of the infected cells while Granzymes goes into the cell and kill the infected cells leading to Cell Death (apoptosis).
Cytokines are also known as messanger molecules, and they are proteins produced by cells to modulate the growth and the function of cells in the body. These cells include the Immune System Cells, and Blood Cells. Cytokines will cause either Accute or Chronic Inflammation in cells where acute will be short-termed and chronic will be long termed. Looking at immune system, certain cytokines are produced in acute inflammation, and they include the Tumor Necrosis Factor (TNF), Interleukin-1, Interleukin-6, Interleukin-7, and Chemokines. In Chronic inflammation there can be Cytokines such as Interleukin-12, Interleukin-17, and Interferon Gamma. Other Interleukins are Interleukin-2, Interleukin-3, Interleukin-8, Interleukin-4, Interleukin-10, interleukin-5, and Interleukin-6. I will create a post on Interleukins properly.
T-Helper cells (TH) or CD4+ cell, are a center for whole immune system that perform as it plays a major role in Humoral and Cell mediated immunity. With antigens in the body, the antigen presenting cells will utilize the major histocompatibility complex class 2 (MHC-2) molecules to identify the antigens. When this is done, CD4+ cell binds with the antigen presenting cell with the T cell receptors which then binds to the antigen. The T-helper cell becomes matures and stars to release interleukins and binds to the B-cell which contains CD40 ligand, after which antibodies are released from the B-cells to the antigens. There are three types of B-Cells which produces different types of antibodies which includes IgA antibodies alone, IgM antibodies alone, and the third releases IgE and IgG antibodies.
There are two types of T-Cell which are the CD4+ cell, and the Cytotoxic T-Cell. while MHC-2 binds with CD4+ cell, MHC-1 binds with Cytotoxic T-Cells. Cytotoxic T-cell also known as Killer T-cells (CD8+ cells) are known as cancer killer cells. When the Antigen gets into the body, it is identified by the antigen presenting cell (target cell) which consists of major histocompatibility complex class 2 (MHC-1) molecules after which Cytotoxic T-cell will bind to the target cell. This cell gets divided intn Cytotoxic memory cell, and Effector Cytotoxic T lymphocyte. The memory cell will help indentify the antigen the next time it invades the body, and the effector cytotoxic T-lymphocyte stars to release perforins and granzymes into the antigen cells and begin to for pores on the cells of the antigen. These pores on the infected cell allows the enzymes to enter the cells and kill the antigens leading to cell death.
Citation
- https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2785020/
- https://www.cancer.org/treatment/treatments-and-side-effects/treatment-types/immunotherapy/cytokines.html
- https://www.ncbi.nlm.nih.gov/books/NBK565844/
- https://www.nature.com/articles/ni1582
- https://www.ncbi.nlm.nih.gov/books/NBK26846/
- https://medlineplus.gov/ency/article/000821.htm
- https://www.ncbi.nlm.nih.gov/books/NBK21070/
- https://www.ncbi.nlm.nih.gov/books/NBK26827/
The body is naturally prepared to fight antigens. There are times I just let my body do its natural defense mechanism before taking steps to treat at the hospital. I have a friend who would never take medication for catarrh that is less 72 hours. he will always say that his immune system should be able to fight that.
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