If there is an immune response, there are of course, things that can bring about the stimulation or the activation of the parts of the Immune System. This is known as the immunogen or what is considered as anything that can actually cause an immune response. If the immunogen causes the entire Immune System to react, there are also substances that can cause parts or specific segments of the said system to react aggressively and these are known as antigens. Antigens are substances that can stimulate one part of the Immune System which can in turn alert other segments eventually leading to the activation of the entire system or the creation of an immune response. Antigens are usually known to be complex and huge molecules that are external to the body. The reason why they are easily detected by the Immune System is the fact that they are found outside the body and they are non-self.
You may also hear about determinants which are actually parts of the antigen that are the ones recognized by the agents of the Immune System. There are certain receptor sites that actually function to recognize antigens as they attempt to enter the body. Not all molecules can be considered as antigens because there are certain factors that affect its ability to become potential threats to the body’s defenses. They should be huge enough and they should be complex as well for them to be recognized as a true antigen. There are such parts of the antigen known as the antigenic determinant that are considered to be immunogenic. Antibodies are said to bind to certain sites as well.
As what have been stated, there are actually receptors which are considered to be molecules that only detect certain patterns and this can only be compatible to the determinants on an antigen. These receptors actually have one recognition site which is the area where the determinant of an antigen binds. They have distinct shapes making the determinant attract to the reception site due to the same 3D shape and the existing van der Waals forces. These receptors are found right on the surface of the cells but contrary to fact that they last there for as long as they could, these receptors can actually shed off.
Receptors are known to have certain characteristics and one of the most significant among them is the fact that they have specificity. This means that certain receptor sites actually fit only to certain determinants and vice versa. It can be very specific in a sense that though the determinant is of the same kind or type, it will still be not recognized if it is not the actual microorganism that the receptor is known to accept.
The body has actually a lot of receptors which are known by the body to be a part of itself. Some examples of the receptors our body can have include receptors for insulin, receptors for steroid hormones and among others. They are considered as a part of the self due to the fact that insulin is naturally a part of our body and its receptor is also considered as a part of it as well. However, when it comes to the antigen, it is entirely different because yes, the receptors for the antigen can be a part of the body or is considered as self but then the antigen itself is known by the body as non self.
If you are wondering what self and non self are all about, you must know that they are two distinct materials that have their own definite characteristics. First of all, self is a term given to substances that are proteins encoded by our very own genes. It means that the determinants are actually made by the individual himself or herself that is why it is very much recognized as self. On the other hand, non self means that the determinant is not part or manufactured by the self in any way. They come from external sources which include microorganisms like viruses, bacteria, fungi, protozoa and helminths.
The antigen receptors which are part of the self recognize the non self materials easily. The antigen receptors include antibodies, T-cell receptors and among others. These receptors are used so that the body can easily identify parts that are considered to be components of the self. The receptors are also considered as the primary means of the body to discriminate or characterize which materials or substances are self and which are non self. As what have been stated, these receptors have their own specificity which should be able to react with non self and will not react to those parts of the self.
Aside from this, there is also what is known as the damage and non damage discrimination. The sensing of damage is actually important as this is mediated by certain receptors. You may not be aware but some parts of the Immune System can actually have receptors that can be able to detect damaged material. The cell also has its own ability, even without the aid or receptors, to detect if it has its own damage. If that is the case, the cell can respond to itself by stopping its usual processes for functioning and eventually generate cell death or cause apoptosis.
These are just some of the important terms and processes that are considered to be a significant part of the Immune System that helps the body strengthen its defenses against any type of pathogen that can cause much of the threat and risk to its normal functioning.