IMMUNOLOGY

Detailed explanation-1: -Antigens are substances (usually proteins) on the surface of cells, viruses, fungi, or bacteria. Nonliving substances such as toxins, chemicals, drugs, and foreign particles (such as a splinter) can also be antigens. The immune system recognizes and destroys, or tries to destroy, substances that contain antigens.

Detailed explanation-2: -An antigen is any kind of marker-like a protein or string of amino acids-that your immune system can recognize. If this definition seems a little vague to you, you’re not alone. Let’s dig in further. Antigens are usually proteins or sugars (polysaccharides) found on the outside of things like cells or viruses.