Imagine the simple game of chess where each piece plays a specific role of conquering the opponent while also protecting their own king. This analogy can be used to explain the functionality of the body immune system. Similarly, just like in the ancient empires, there was a power hierarchy where specific individuals played specific roles in protecting the kingdom. The King was always the supreme leader and had to be protected at all costs. Just like in Chess, there were bishops who were tasked with giving strategic advice to the King, knights who were commanders of the battlefields and the pawns who were basically the soldiers protecting the kingdom from the enemies. In the human body, the immune system is solely responsible for protecting the body from any external invasions which might affect the normal functions. One important fact to note is that the human body is like a battlefield between the cells of the immune system and enemies of microscopic nature. The enemies of the human body can be in the form of microscopic pathogens such as bacteria, viruses, parasites and even fungi that also have the means to breach the body defense systems. These pathogens can get to the body through wounds, mouth, food or even when we breathe.
Back to the battlefield analogy, once the pathogens have gotten into the body system, they multiply and affect the operations within the system by releasing their toxins and killing the body cells which can lead to various illnesses which, most of the time, are fatal. In this case, the pathogens are like the enemy kingdom invading the body kingdom with the immune system acting like the defense system against the attack. This automatically makes the body to be the battlefield. Just like the complex hierarchy in real war, the human immune system is also composed of a complex mechanism that is specifically designed to combat the attacks. To this extent, there are various components and cells within the system which work either independently or in partnership with other cells to partake different roles. As much as the immune system is very complex, its purpose is clearly simple. It is designed to recognize, disable or fight and dispose any external or internal threat. The system also has a memory components which are designed to remember the pathogens in case they return in the future. The immune system has various methods of attack with some components having the capability of engulfing and destroying the pathogens while other components produce substances which are meant to eradicate any foreign body that is considered as threat to the body.
One of the basic components of the immune system is the leucocytes, commonly referred to as the white cells. These cells often circulate within the body through the blood and lymphatic vessels. They are considered as the security patrol of the body are always on the lookout for any pathogen. In case a target is determined, the cells begin to multiply and send signals to other components of the immune system to act. They are stored within the lymphoid organs including the thymus, spleen, the lymph nodes and the bone marrow. One type of the leucocyte is referred to as the phagocyte which works through a mechanism known as phagocytosis. This takes place through surrounding and engulfing of the pathogen effectively eradicating them. The neutrophils are types of phagocytes which specialize in attacking bacteria while the macrophages are used for removal of the already dead cells. The mast cells, which are also phagocytes, are used for healing purposes and for defense. Another type of leucocyte is the lymphocyte which is used as a memory for remembrance and recognition of any previous invaders. The B-lymphocytes and the T-lymphocytes are the main the main types of lymphocytes with the former producing antibodies while the former helps in destroying any compromised cells within the body while also alerting other leucocytes.
In the same class as lymphocytes, are the Natural Killer (NK) cells. The NK cells originates from the same progenitor like the T and B lymphocytes. They are the cells of the innate immune system and mostly kills cells which have been infected by viruses. There are also some specialized NK cells which play critical roles during pregnancy and are often found in the placenta. They also have the capability to secrete cytokines which enhance the response of other immune cells such as the Macrophages and the dendritic cells. Apart from the NK cells, there are also the cytotoxic T-lymphocytes which also directly attack other cells which are considered as foreign to the body system. They are particularly used to fight cells which have been infected with viruses, cancer cells, allografts as well as cells infected with bacteria and parasites. It should be noted that the cytotoxic T-lymphocytes are a subset of the T-cells and use the T-cell receptor. They can therefore recognize antigens within the Class 1 histocompatibility molecules. (MHC). They work by binding to the target and discharging which digests and kills the cell.
The Helper-T cells is also another critical component of the adaptive immune system considering they are a necessity in all the adaptive immune responses. First, they are critical in the activation of the B-cells and macrophages in the secretion of the antibodies and destroying any ingested microbe respectively. These cells are also important in activation of the already discussed cytotoxic T-cells which kills the infected target cells. An important concept to take into consideration is the fact that the Helper-T cells are only functional on activation to become effector cells. The activation takes place on the antigen presenting cells which are also triggered by an infection. The other important cells of the immune system are the follicular dendritic cells (FDCs) which are responsible for the selection of the B-lymphocytes cell. Their main function include the presentation of the antigens to the memory cells which binds to the B-cell receptors. The follicular dendritic cells are found within the follicles of the lymphoid organs. It is important to note that the FDCs are developed on the basis of the conditions which drives the precursor cell into maturation.
Another type of the leucocyte which is also an important component of the immune system is the plasma cells. They are derived from the B cells through the process of differentiation. Once produced, the plasma cells shall produce antibody molecules following the pattern that has been modelled by the precursor B cell. The produced antibody molecules are then released into the blood and the lymph after which they can bind to a targeted antigen and initiating its neutralization process or elimination. The process of the production of the antibodies is continual and is highly dependent on the availability of the antigen within the body. The process of the differentiation of the B-cell takes place from the hematopoietic stem cell (HSC) within the bone marrow. The process of the development and the differentiation of the B cells takes place in different phases. First, immunocompetent B cells that can bind to any unique antigen are generated. This process involves the proliferation of the progenitor B cell and rearrangement of genes to produce specific regions which can bind to the antigen. The B-cells are then further matured into follicular cells which takes place through activation and co-stimulation. Specific signals is what promote the differentiation of the B cells into either memory B-cells or plasma cells.
Mast cells are also other critical components of the bodily defense mechanism. They also originate from the hematopoietic cells within the bone marrow but from the pluripotent progenitor cells. The maturation of the mast cells takes place under various factors which are provided by the tissue environment apart from the ligand and the stem cell. In most cases, the mature mast cells do not circulate within the bloodstream but their progenitors often migrate between tissues while differentiating at the required places under the influence of cytokines and stem cell factor. In the bodily defense mechanism, the mast cells are responsible for the regulation of the various immune system cells including the dendritic cells, the macrophages and even both the B and T cells. The function through the production and release of the multi-potent molecules which have the capability of regulating the function of the other cells. The mast cells are also very important in the recognition of foreign bodies or antigens in the body. To this extent, they can either directly bind to the pathogens or associate the antigens with the PAMPs on their surface. They have receptors on their surface which are used for binding and release of mediators which eliminates the pathogen in the process.
The other important components of the immune system include the basophil, eosinophil and the neutrophil which are the basic white blood cells just like the mast cells and other discussed cells. First, the basophils are specifically designed to respond to short-term inflations such as allergies and irritation. They function through the release of cytokines that causes the swelling of the veins which causes vasodilation during the inflammation. On the other hand, the eosinophils are specifically responsible for tackling any infections from parasites. They can also work in conjunction with the basophil in controlling allergic reactions. Lastly, the neutrophils act as defense systems against any infection emanating from either bacteria or fungi. They can also control any infection that causes small inflammatory processes. Whenever there is a microbial infection in the body, the neutrophils are the first line of the defense. They are often produced in large quantities and die to form pus which is as a result of degranulation. From the analysis, it is very apparent how the various components of the immune system operate to protect the body from any form of harm. Just like the earlier comparison, it can be hypothesized that the discussed cells form different pieces within the chess board which in this case is represented by the human body. It can only be quite challenging to identify the exact piece within the chess board.