Immunopathology is a branch of medicine that deals with immune responses associated with disease. It includes the study of the pathology of an organism, organ system, or disease with respect to the immune system, immunity, and immune responses. In biology, it refers to damage caused to an organism by its own immune response, as a result of an infection. It could be due to mismatch between pathogen and host species, and often occurs when an animal pathogen infects a human (e.g. avian flu leads to a cytokine storm which contributes to the increased mortality rate).
Types of Immunity
In all vertebrates, there are two different kinds of immunities: Innate and Adaptive immunity. Innate immunity is used to fight off non-changing antigens and is therefore considered nonspecific. It is usually a more immediate response than the adaptive immune system, usually responding within minutes to hours. It is composed of physical blockades such as the skin, but also contains nonspecific immune cells such as dendritic cells, macrophages, and basophils. The second form of immunity is Adaptive immunity. This form of immunity requires recognition of the foreign antigen before a response is produced. Once the antigen is recognized, a specific response is produced in order to destroy the specific antigen. Because of its tailored response characteristic, adaptive immunity is considered to be specific immunity. A key part of adaptive immunity that separates it from innate is the use of memory to combat the antigen in the future. When the antigen is originally introduced, the organism does not have any receptors for the antigen so it must generate them from the first time the antigen is present. The immune system then builds a memory of that antigen, which enables it to recognize the antigen quicker in the future and be able to combat it quicker and more efficiently. The more the system is exposed to the antigen, the quicker it will build up its responsiveness. Nested within Adaptive immunity are the Primary and Secondary Immune Responses.
The Primary Immune Response refers to the first exposure and subsequent response of the immune system to a pathogen. During this initial response, the immune system identifies and targets the pathogen through various mechanisms, including the activation of immune cells such as T cells and B cells, which produce antibodies that specifically target the pathogen. The Secondary Immune Response occurs upon subsequent encounters with the same pathogen. During the Primary Immune Response, memory cells are generated that remember the specific pathogen and how to target it. When the same pathogen enters the body again, the memory cells are quickly activated, leading to a faster and more efficacious response compared to the primary immune response. This results in more effective elimination of the pathogen. Vaccines serve to activate the Primary Immune Response through exposure to weakened or less dangerous antigens, preparing the body's memory cells for the purpose of the immune system being more equipped to handle the equivalent full scale antigen.