> See also: > - Reference # Antigens An **antigen** is any molecule or molecular fragment that either is recognized by an [[Antibodies|antibody/BCR]] or can be bound by an [[Major Histocompatibility Complex (MHC)|MHC]] molecule and presented to a [[T-Cells|T-Cell Receptor]] > [!info]- Key Features of Antigens 🦠 > An **antigen** is anything that a BCR or TCR can bind to. > > Generally speaking, an **antigen** is any toxin/foreign material that is associated with a specific pathogen; these are always [[biological macromolecules]] (often [[Proteins|proteins]] or [[carbohydrates]]) that the pathogen > > **Immunogens** are antigens which will induce an immune response when bound to a TCR/BCR --- Some small antigens may not trigger an immune response (they are not immunogenic). However, it is possible for them to become immunogenic if they are attached to a larger host protein. In this situation, the small antigen is known as a **hapten**. The activation of ## Antigen Presentation - [[Dendritic Cells]] - [[T-Cells]]?