Define Immunity in Biology

Immunity refers to the body's capacity to fend off pathogen invasion. People are constantly exposed to pathogens, which are foreign agents that cause disease. Examples of these agents include bacteria and viruses. Pathogens have antigens attached to their surfaces, which cause the immune system to respond. The body's defense mechanism against antigens and for bodily protection is the immunological response.

Immunity can be of the following types: Innate immunity, passive immunity, and acquired/active immunity

Innate immunity: Innate immunity, also known as nonspecific immunity, refers to a person's innate, inherent resilience. It offers resistance against the pathogen using various physical, chemical, and biological techniques. Epithelial layers are where microbes first come into contact (physical barriers that line our skin and mucous membranes). General defenses include fever, a phagocytic activity linked to the inflammatory response, antibacterial compounds, chemical signals (cytokines), and released chemical signals. The cell surface receptors on the phagocytes can bind to and react to typical molecular patterns expressed on the surface of invading microorganisms. These methods allow innate immunity to stop the invasion, dissemination, and colonization of microorganisms.

Passive immunity: The ability of the body to fight against viruses by "borrowing" antibodies is known as passive immunity. For instance, blood components containing antibodies, such as immunoglobulin, which can be transfused from one person to another, or antibodies found in breast milk can pass to a baby. This type of passive immunity newborns typically acquires from their mothers. In the final one to two months of pregnancy, antibodies are moved through the placenta. A full-term baby will therefore have the same antibodies as its mother. These antibodies function to defend against particular antigens and will shield the newborn from some diseases for up to a year.

acquired/active immunity: The immunity of the acquired (adaptive) variety arises from immunological memory. A specific antigen (associated with a pathogen) is presented to the body, which then produces antibodies against that antigen (Khan Academy, n.d.). The body has a memory of the specific antigen and has antibodies to ward it off the next time it invades. When a person is exposed to an infection, they may develop acquired immunity, which makes them immune to future infections. In cases where the vaccine imitates a specific disease and triggers an immune response in the recipient without making them sick, this is known as acquired immunity.