What is an antigen?
An Antigen causes a response in the immune system of the organism that is hosting the antigen. The antigen can sometimes be a good part of the host. However, the one factor about the antigen is that it causes the body to create antibodies to take care of the antigen problem. The immune system creates an antibody that is a match to the antigen that is causing problems in the immune system. Each antibody has adaptations to the region which allows it to adapt so that it can adequately take care of the antigen. This also allows for the production for many different antibodies. Many different antigens will have a match in the form of a specific antibody. An antibody is only able to bind one antigen in most cases. However, there are antibodies that can bind multiple antigens.
The antigen binds itself to receptors that are specific to the antigen. However, it often takes more than just the antigen to induce an immune response. The normal types of antigens are polysaccharides, lipids, or peptides. Generally, there are some antigens that are not immunogens due to its inability to bring forth an immune response. Peptides are very small in size. Therefore, it does not cause an alarm in the immune system. The larger antigens will bring forth a response in the immune system.
Types of antigens
There are two types of antigens that the body deals with as it relates to the immune system. There are the antigens that originate in the body, and there are those that come from outside of the body. The antigens that originate from inside the human body do not typically generate a reaction when conditions are normal. This comes from a lack of T cells in the thymus. The purpose of the antibody is to identify a foreign antigen that is invading the immune system and take care of the agent in order to preserve the health of the human body. However, things are different conditions are distressed.
Cells that present antigens typically release peptides on the platform of histocompatibility molecules. The antigens are typically identified by T cells. The activation of T cells depend on the antigen and hystocompatibility molecule. The peptide is to be broken into tiny bits in the T cell in order for it to be recognized by the T-Cell Receptor. The antigen needs the assistance of some kind of immunologic adjuvant in order to trigger a response in the immune system.
There are antigens that are able to trigger a response in the immune system. These are called immunogens. The immune response that occurs as a result of the immunogen is cell-mediated. There is also a humoral immune response that can be triggered by the immunogen. This occurs in stages. The first phase of the immune response is the innate immune response. This leads to the adaptive immune response. This is when the antigen combines with the products of the immunoreceptor which vary greatly. The immunoreceptor products are T-cell receptors and B-cell receptors.
One of the traits that characterizes an immunogen is its ability to connect with the variable Fab region of an antibody. One ability that an antibody has is the ability to use discretion when it comes to epitopes that are visible on the surface of an antibody. One thing that an antigen could carry is a small molecule called hapten. This has a large influence on the antigenic epitope's structure. This one ability that is actually amazing among other traits of antibodies. This shows some sort of precision in the creation of these antibodies.
To be specific, antigens are polysaccharides and proteins. In some cases, they might even be lipids. When they are combined with certain proteins, then lipids and nucleic acids can become antigenic. There are many outside agents that could become antigens. Among the agents that are potentially antigenic are egg whites, pollen, transplanted tissue proteins and plenty of other agents that could cause a reaction of the immune system in order to take care of the invasion. These outside antigens are also known as non-microbal or non-self antigens. One outside source of imunogenic antigens are vaccines. They are often given to people in order to prepare themselves for a potential illness.
Outside antigens are known as exogenous antigens. The common way that these antigens enter the body is through inhalation, injection, or ingestion. Often times, the immune system reacts to the antigens in a less than clinical fashion. The process of the antibodies taking on the antigens are either endocytosis or phagocytosis. These antigens are brought to the cells that present antigens. The antigens are then broken down into pieces so that they can be processed. The pieces are taken to the T helper cells so that they can process the molecules with the secretion of substances.
There are also the endogenous antigens. They occur as a result of the metabolism of the cells. Other factors that play into the development of endogenous antigens are intracellular bacterial infections, or viral infections. The endogenous antigens that activate the immune system are broken down into bits and then presented on the surface of the cell with certain molecules. The T cells will recognize the infected cells and take measures to keep the cell from dying from the cytotoxic cells. Among the measures that the T cells is releasing toxins in order to protect the cell. Tolerance can result in the elimination of cytotoxic cells.
Antigens are the agents that are considered a threat to the health of the immune system. The immune system is one very fascinating system that has an amazing structure and procedure for handling different types of antigens. Other types of antigens besides the endogenous antigen and exogenous antigen are autoantigens and neoantigens. Some of these are recognized in autoimmune disease. The neoantigens are not found in normal humans. The neoantigens are more involved in the control of tumors. Due to the diversity of antigens, the human body produces the antibody that is specific to the antigen that is discovered in the body.