What is an antigen made out of?

An antigen is typically made up of proteins, polysaccharides, or glycoproteins that are found on the surface of pathogens like bacteria, viruses, or fungi, as well as on the surfaces of cells. These molecules can also be derived from non-pathogenic substances, such as pollen or food proteins. Antigens are recognized by the immune system, specifically by antibodies or T-cell receptors, triggering an immune response. Their unique structures enable the immune system to distinguish between self and non-self components.