Final answer:
An antigen, often a protein also called an immunogen, is a substance that can induce a state of sensitivity or immunity. Antigens contain epitopes that trigger specific immune responses. Hypersensitivities are often negative reactions to such antigens, ranging from mild to severe.
Step-by-step explanation:
The name for any substance that can induce a state of sensitivity or immunity in the body, often after a latent period, is known as an antigen. These substances are typically proteins referred to as immunogens, and they are capable of activating the adaptive immune system. Antigens contain smaller units called epitopes, which elicit specific immune responses. When antigens are recognized, they are processed by cells like macrophages and presented to other cells in the immune system, sparking a complex cascade of events that can lead to immunity or, in the case of hypersensitivities, to harmful reactions against harmless substances.
Hypersensitivities are maladaptive immune responses to antigens, which can be immediate, delayed, or autoimmune in nature. For instance, Type I Hypersensitivities occur when a sensitized individual is exposed to an allergen, leading to an allergic reaction. Such reactions can be mild, like sneezing and itchy eyes, or severe, including life-threatening anaphylactic responses. Interferons, mannose-binding protein, and C-reactive protein are examples of early induced proteins that play a role in the innate immune response to antigens. They facilitate processes such as opsonization, enhancing the immune system's ability to deal with pathogens.