Immunity is the body’s ability to stay safe from germs and other substances that might make you ill. It is made up of many organs, cells and proteins that work in tandem to detect and fight infection. Immunity involves lines of defense against most microbes and specialized and highly specific responses to particular offenders. These are referred to as the innate and adaptive immune response.
Innate immunity is the first line of defense against bacteria, viruses, fungi and other organisms that can cause disease. Antibodies and complement systems are the primary innate mechanisms that recognize pathogens. Upon recognition, these two components initiate the inflammatory response by binding to and neutralizing the pathogens, or facilitating phagocyte uptake by opsonization. The inflammatory response also includes the release of chemicals such as histamines and leukotrienes, which cause vasodilation and increased tissue permeability, respectively. These chemicals also recruit neutrophils and macrophages to the area. Innate immunity also includes the production of cytokines, which facilitate cell-cell communication and activate other immune cells.
Adaptive immunity is the second part of the body’s immune system. After a bacterium or virus invades the body, T cells and B cells are activated. The T cells help the innate immune system fight the infection and produce antibodies against the pathogens. These antibodies can either directly kill the bacterial or viral envelope or block the entry of the germ into normal tissues.
The adaptive immune response also produces memory cells that can remember the specifics of each invader and mount a fast and targeted response when the pathogen is encountered again. Naturally acquired active immunity can also occur in the form of vaccines, which contain antigens that stimulate a primary response and lead to immunological memory.
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