We also have the Natural Killer Cells, these cells can efficiently detect when our own cells have gone rogue, or are infected with, say, a virus. NKC’s detect a protein produced by normal cells, called the Major Histocompatibility Complex or MHC. Basically, whenever a cell isn’t normal, it stops producing this protein. The NKCs move around constantly, checking our cells for this type of deficiency, and when they find an abnormal cell, they simply bind to it and release chemicals that will destroy it. The last cells of our innate immune system are the dendritic cells. These are found in places that come in contact with the outside environment, such as the nose, lungs, etc. They are the link between our innate and adaptive immune systems. They eat a pathogen, and then carry information about it to our adaptive immune system cells.
This information is produced and shared in the form of antigens. Antigens are the traces that pathogens leave around. They are molecules found on the surface on pathogens that can be detected by our adaptive immune system for recognition. The dendritic cells pass on this information to our T cells. However, macrophages can also perform this function.
Now, there is also the adaptive or acquired immune system. This system is more efficient, as it can differentiate between different types of pathogens. It has 2 main components – T lymphocytes and B lymphocytes. T-cells come into play when an infection has already occurred, thus bringing about the cell-mediated immune response. B-cells join the fight when the pathogens have entered, but haven’t yet caused any disease. This is called the humoral immune response. Some T-cells take signals from the dendritic cells or macrophages, and are thus called helper T-cells. They perform two key tasks: forming effector T-cells, which are basically cells that cycle through the body and call in the cavalry, namely other white blood cells. Helper T-cells also form memory T-cells, which keep a record of this antigen for future reference. Sometimes, the some cells of our body know that they have lost the battle.
Essentially, the affected area or organ has become heavily infected with pathogens, so there is no hope for them. At this point, the immune system brings out the cytotoxic t cells. These cells rush over and perform a mercy killing for the infected and dying cell. Furthermore, we have the B-cells, They produce chemicals called antibodies, which fit on the antigens of pathogens, much like how a lock and key fit together. These antibodies crowd around a pathogen and act like tags. They signal the macrophages to come and kill the marked pathogen. B-cells also produce memory B-cells when they encounter an antigen. The B- and T- memory cells jointly maintain a record of all encountered infections, and thus strengthen and solidify the body’s immune response to these infections. Our innate immune response is quicker, though non-specific. It gets into action within hours and is pretty strong.
However, when things get out of hand, the innate system calls for help from the acquired immune system. This system can take days to mount a response, but the next time we encounter that pathogen, it won’t make us get sick. In short, every day that we spend being healthy is all thanks to our immune system. So, it definitely deserves our respect.