how antigne is formed
An antigen is formed when a foreign substance enters the body. The immune system recognizes the substance as foreign and begins to produce antibodies, which are proteins that bind to the antigen and help the immune system to destroy it. As the immune system continues to be exposed to the same antigen over time, it becomes better at recognizing and fighting it, leading to the development of immunity. Antigens can include bacteria, viruses, fungi, and other substances that are not normally found in the body. Some antigens, such as those found on cancer cells, can also be produced by the body itself.
Antigens are foreign substances that enter the body and trigger an immune response. They can be molecules or particles derived from pathogens such as bacteria, viruses, fungi, or parasites. Here is a step-by-step explanation of how antigens are formed:
1. Pathogen invasion: Antigens are formed when a pathogen enters the body. This can occur through various routes, such as inhalation, ingestion, or direct contact with the skin.
2. Pathogen replication: Once inside the body, the pathogen begins to replicate, increasing its numbers. This replication process allows the pathogen to spread and establish an infection.
3. Pathogen components: As the pathogen replicates, it produces various components known as antigens. These antigens can be found on the surface of the pathogen or released into the surrounding environment.
4. Structural features: Antigens can have different types of structural features. Some antigens are proteins, such as surface proteins on bacteria or viral proteins, while others are carbohydrates or lipids found in the outer layers of the pathogen.
5. Recognition by the immune system: Antigens are recognized by the immune system as foreign substances. This recognition occurs when specialized cells of the immune system, including antigen-presenting cells (APCs) like dendritic cells or macrophages, encounter the antigens.
6. Antigen presentation: The antigen-presenting cells engulf the pathogens and break them down into smaller fragments. These fragments are then displayed on the cell surface using a protein called major histocompatibility complex (MHC) molecules.
7. Activation of immune response: When antigens are presented to immune cells called T cells, the T cells become activated. This activation triggers a cascade of immune responses, including the production of antibodies by B cells and the activation of other immune cells to eliminate the pathogen.
In summary, antigens are formed when pathogens invade the body, replicate, and produce various structural components. These antigens are recognized by the immune system, leading to an immune response to eliminate the pathogen.