IMMUNOLOGY

Detailed explanation-1: -Prions and viruses are not regarded as living things because they fall short of a few key requirements for life. For instance, viruses and prions do not contain cells and do not have an energy metabolism system. They lack any cell organelles, hence they are unable to carry out any type of metabolic activity.

Detailed explanation-2: -Non-cellular pathogens are microorganisms that are not composed of cells, such as viruses and prions, unable to reproduce or grow on their own and need a host cell to do so, which are often treated differently than cellular pathogens.

Detailed explanation-3: -The prion protein exists in multiple conformations and its cellular isoform, PrPC, which is found in healthy organisms, is among the most extensively studied proteins.

Detailed explanation-4: -And once again, this includes viruses, viral roids and prions are the three groups of a cellular infectious agents.