* Self-antigens: These are molecules that are normally present on the surface of your own cells. They are usually not recognized as foreign by your immune system.
* Non-self antigens: These are molecules that are not normally present on the surface of your cells. They can be found on:
* Pathogens: These are disease-causing organisms such as bacteria, viruses, fungi, and parasites.
* Foreign cells: These are cells from other organisms, such as those from a blood transfusion or organ transplant.
* Allergies: These are caused by the immune system overreacting to normally harmless substances, such as pollen or dust mites.
Cells that express antigens:
* All cells in the body: All cells express some self-antigens, which are important for distinguishing your own cells from foreign cells.
* Infected cells: When a cell is infected by a pathogen, it may express non-self antigens from the pathogen. These antigens are recognized by the immune system, leading to an immune response against the pathogen.
* Cancer cells: Cancer cells often express abnormal antigens, which can be recognized by the immune system. This allows for the development of cancer immunotherapies.
The process of antigen presentation:
* Antigen-presenting cells (APCs): These are specialized cells that take up antigens and display them on their surface to T cells, which are a type of immune cell that can recognize and destroy cells presenting foreign antigens. Examples of APCs include macrophages, dendritic cells, and B cells.
In summary:
* Cells don't produce antigens, they express them.
* All cells express self-antigens.
* Cells can express non-self antigens from pathogens, foreign cells, or allergens.
* Antigen-presenting cells (APCs) play a crucial role in presenting antigens to the immune system.
