PATHOLOGY

Detailed explanation-1: -In an immune response, the immune system recognizes the antigens (usually proteins) on the surface of substances or microorganisms, such as bacteria or viruses, and attacks and destroys, or tries to destroy, them. Cancer cells also have antigens on their surface.

Detailed explanation-2: -Vaccination (immunization) is a way to trigger the immune response. Small doses of an antigen, such as dead or weakened live viruses, are given to activate immune system “memory” (activated B cells and sensitized T cells). Memory allows your body to react quickly and efficiently to future exposures.

Detailed explanation-3: -The immune reaction that results from immediate hypersensitivities in which an antibody-mediated immune response occurs within minutes of exposure to a usually harmless antigen is called an allergy.