Immunopathology

Last updated

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). [1]

Contents

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. [2] 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. [2] 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. [2] 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. [2] 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. [3]

Improper Immune Responses

When a foreign antigen enters the body, there is either an antigen specific or nonspecific response to it. These responses are the immune system fighting off the foreign antigens, whether they are deadly or not. A possible definition of Immunopathology is how the foreign antigens cause the immune system to have a response or problems that can arise from an organism's own immune response on itself. There are certain problems or faults in the immune system that can lead to more serious illness or disease. These diseases can come from one of the following problems. The first would be Hypersensitivity reactions, where there would be a stronger immune response than normal. There are four different types (type one, two, three and four), all with varying types and degrees of an immune response. The problems that arise from each type vary from small allergic reactions to more serious illnesses such as tuberculosis or arthritis. The second kind of complication in the immune system is Autoimmunity, where the immune system would attack itself rather than the antigen. Inflammation is a prime example of autoimmunity, as the immune cells used are self-reactive. A few examples of autoimmune diseases are Type 1 diabetes, Addison's disease and Celiac disease. The third and final type of complication with the immune system is Immunodeficiency, where the immune system lacks the ability to fight off a certain disease. The immune system's ability to combat it is either hindered or completely absent. The two types are Primary Immunodeficiency, where the immune system is either missing a key component or does not function properly, and Secondary Immunodeficiency, where disease is obtained from an outside source, like radiation or heat, and therefore cannot function properly. Diseases that can cause immunodeficiency include HIV, AIDS and leukemia. [2]

Cancer

The immune system plays an important role in protecting the body against cancer. The immune response to cancer can be categorized into the two main categories as discussed above: innate immunity and adaptive immunity.

Innate immunity is the first line of defense against cancer. It consists of non-specific immune cells that can recognize and destroy abnormal cells, including cancer cells. Natural killer (NK) cells, dendritic cells, and macrophages are some examples of innate immune cells that can detect and eliminate cancer cells. [4]

Adaptive immunity, on the other hand, is more specific and targeted. It involves the activation of T cells and B cells, which can recognize and attack cancer cells that have specific antigens on their surface. T cells can directly kill cancer cells or help activate other immune cells to attack cancer cells. B cells can produce antibodies that recognize and neutralize cancer cells. [5]

However, cancer cells can evade immune surveillance and escape destruction by the immune system through various mechanisms, including downregulating antigen presentation, producing immunosuppressive molecules, and inhibiting T cell function. This can lead to the development and progression of cancer. [5]

Immunotherapy is a type of cancer treatment that aims to harness and enhance the immune system's ability to recognize and attack cancer cells. Some examples of immunotherapies include checkpoint inhibitors, which block molecules that inhibit T cell activation, and CAR-T cell therapy, which involves modifying T cells to recognize and attack cancer cells more efficiently. [5]

Related Research Articles

<span class="mw-page-title-main">Antigen</span> Molecule triggering an immune response (antibody production) in the host

In immunology, an antigen (Ag) is a molecule, moiety, foreign particulate matter, or an allergen, such as pollen, that can bind to a specific antibody or T-cell receptor. The presence of antigens in the body may trigger an immune response.

<span class="mw-page-title-main">Immune system</span> Biological system protecting an organism against disease

The immune system is a network of biological systems that protects an organism from diseases. It detects and responds to a wide variety of pathogens, from viruses to parasitic worms, as well as cancer cells and objects such as wood splinters, distinguishing them from the organism's own healthy tissue. Many species have two major subsystems of the immune system. The innate immune system provides a preconfigured response to broad groups of situations and stimuli. The adaptive immune system provides a tailored response to each stimulus by learning to recognize molecules it has previously encountered. Both use molecules and cells to perform their functions.

<span class="mw-page-title-main">Immunology</span> Branch of medicine studying the immune system

Immunology is a branch of biology and medicine that covers the study of immune systems in all organisms.

<span class="mw-page-title-main">Autoimmunity</span> Immune response against an organisms own healthy cells

In immunology, autoimmunity is the system of immune responses of an organism against its own healthy cells, tissues and other normal body constituents. Any disease resulting from this type of immune response is termed an "autoimmune disease". Prominent examples include celiac disease, diabetes mellitus type 1, Henoch–Schönlein purpura, systemic lupus erythematosus, Sjögren syndrome, eosinophilic granulomatosis with polyangiitis, Hashimoto's thyroiditis, Graves' disease, idiopathic thrombocytopenic purpura, Addison's disease, rheumatoid arthritis, ankylosing spondylitis, polymyositis, dermatomyositis, and multiple sclerosis. Autoimmune diseases are very often treated with steroids.

An immune response is a physiological reaction which occurs within an organism in the context of inflammation for the purpose of defending against exogenous factors. These include a wide variety of different toxins, viruses, intra- and extracellular bacteria, protozoa, helminths, and fungi which could cause serious problems to the health of the host organism if not cleared from the body.

In biology, immunity is the state of being insusceptible or resistant to a noxious agent or process, especially a pathogen or infectious disease. Immunity may occur naturally or be produced by prior exposure or immunization.

<span class="mw-page-title-main">Lymphocyte</span> Subtype of white blood cell

A lymphocyte is a type of white blood cell (leukocyte) in the immune system of most vertebrates. Lymphocytes include T cells, B cells, and innate lymphoid cells, of which natural killer cells are an important subtype. They are the main type of cell found in lymph, which prompted the name "lymphocyte". Lymphocytes make up between 18% and 42% of circulating white blood cells.

Humoral immunity is the aspect of immunity that is mediated by macromolecules – including secreted antibodies, complement proteins, and certain antimicrobial peptides – located in extracellular fluids. Humoral immunity is named so because it involves substances found in the humors, or body fluids. It contrasts with cell-mediated immunity. Humoral immunity is also referred to as antibody-mediated immunity.

<span class="mw-page-title-main">Cell-mediated immunity</span> Immune response that does not involve antibodies

Cellular immunity, also known as cell-mediated immunity, is an immune response that does not rely on the production of antibodies. Rather, cell-mediated immunity is the activation of phagocytes, antigen-specific cytotoxic T-lymphocytes, and the release of various cytokines in response to an antigen.

Opsonins are extracellular proteins that, when bound to substances or cells, induce phagocytes to phagocytose the substances or cells with the opsonins bound. Thus, opsonins act as tags to label things in the body that should be phagocytosed by phagocytes. Different types of things ("targets") can be tagged by opsonins for phagocytosis, including: pathogens, cancer cells, aged cells, dead or dying cells, excess synapses, or protein aggregates. Opsonins help clear pathogens, as well as dead, dying and diseased cells.

<span class="mw-page-title-main">Adaptive immune system</span> Subsystem of the immune system

The adaptive immune system, also known as the acquired immune system, or specific immune system is a subsystem of the immune system that is composed of specialized cells, organs, and processes that eliminate pathogens specifically. The acquired immune system is one of the two main immunity strategies found in vertebrates.

<span class="mw-page-title-main">Antigen-presenting cell</span> Cell that displays antigen bound by MHC proteins on its surface

An antigen-presenting cell (APC) or accessory cell is a cell that displays an antigen bound by major histocompatibility complex (MHC) proteins on its surface; this process is known as antigen presentation. T cells may recognize these complexes using their T cell receptors (TCRs). APCs process antigens and present them to T cells.

<span class="mw-page-title-main">Innate immune system</span> Immunity strategy in living beings

The innate immune system or nonspecific immune system is one of the two main immunity strategies in vertebrates. The innate immune system is an alternate defense strategy and is the dominant immune system response found in plants, fungi, prokaryotes, and invertebrates.

<span class="mw-page-title-main">Toll-like receptor 2</span> Cell surface receptor found in humans

Toll-like receptor 2 also known as TLR2 is a protein that in humans is encoded by the TLR2 gene. TLR2 has also been designated as CD282. TLR2 is one of the toll-like receptors and plays a role in the immune system. TLR2 is a membrane protein, a receptor, which is expressed on the surface of certain cells and recognizes foreign substances and passes on appropriate signals to the cells of the immune system.

Host tropism is the infection specificity of certain pathogens to particular hosts and host tissues. This explains why most pathogens are only capable of infecting a limited range of host organisms.

<span class="mw-page-title-main">Polyclonal B cell response</span> Immune response by adaptive immune system

Polyclonal B cell response is a natural mode of immune response exhibited by the adaptive immune system of mammals. It ensures that a single antigen is recognized and attacked through its overlapping parts, called epitopes, by multiple clones of B cell.

A non-specific immune cell is an immune cell that responds to many antigens, not just one antigen. Non-specific immune cells function in the first line of defense against infection or injury. The innate immune system is always present at the site of infection and ready to fight the bacteria; it can also be referred to as the "natural" immune system. The cells of the innate immune system do not have specific responses and respond to each foreign invader using the same mechanism.

Protective autoimmunity is a condition in which cells of the adaptive immune system contribute to maintenance of the functional integrity of a tissue, or facilitate its repair following an insult. The term ‘protective autoimmunity’ was coined by Prof. Michal Schwartz of the Weizmann Institute of Science (Israel), whose pioneering studies were the first to demonstrate that autoimmune T lymphocytes can have a beneficial role in repair, following an injury to the central nervous system (CNS). Most of the studies on the phenomenon of protective autoimmunity were conducted in experimental settings of various CNS pathologies and thus reside within the scientific discipline of neuroimmunology.

Autoimmune retinopathy (AIR) is a rare immunological disease in which the patient's immune system attacks proteins in the retina, leading to loss of vision. Researchers do not yet fully understand the disease, but it may be the result of cancer or cancer chemotherapy. Autoimmune retinopathy is an autoimmune condition characterized by vision loss, blind spots, and visual field abnormalities. Autoimmune retinopathy can be divided into paraneoplastic (PAIR) or non-paraneoplastic (nPAIR). The nPAIR division can be further divided into cancer-associated retinopathy (CAR) and melanoma-associated retinopathy (MAR). The condition is associated with retinal degeneration, when autoimmune antibodies recognize retinal proteins as antigens and target them, leading to retinal degeneration.

Immunological memory is the ability of the immune system to quickly and specifically recognize an antigen that the body has previously encountered and initiate a corresponding immune response. Generally, they are secondary, tertiary and other subsequent immune responses to the same antigen. The adaptive immune system and antigen-specific receptor generation are responsible for adaptive immune memory.

References

  1. ↑ Us D (April 2008). "[Cytokine storm in avian influenza]". Mikrobiyoloji Bulteni. 42 (2): 365–380. PMID   18697437.
  2. 1 2 3 4 5 Chaplin, David D. (February 2010). "Overview of the immune response". Journal of Allergy and Clinical Immunology. 125 (2): S3–S23. doi:10.1016/j.jaci.2009.12.980. PMC   2923430 . PMID   20176265.
  3. ↑ Sallusto, Federica; Lanzavecchia, Antonio; Araki, Koichi; Ahmed, Rafi (October 2010). "From Vaccines to Memory and Back". Immunity. 33 (4): 451–463. doi:10.1016/j.immuni.2010.10.008. PMC   3760154 . PMID   21029957.
  4. ↑ Shimoda, Shinji; Hisamoto, Satomi; Harada, Kenichi; Iwasaka, Sho; Chong, Yong; Nakamura, Minoru; Bekki, Yuki; Yoshizumi, Tomoharu; Shirabe, Ken; Ikegami, Toru; Maehara, Yoshihiko; He, Xiao-Song; Gershwin, M. Eric; Akashi, Koichi (December 2015). "Natural killer cells regulate T cell immune responses in primary biliary cirrhosis". Hepatology. 62 (6): 1817–1827. doi:10.1002/hep.28122. ISSN   0270-9139. PMC   4681684 . PMID   26264889.
  5. 1 2 3 Sottile, Rosa; Tannazi, Milad; Johansson, Maria H.; Cristiani, Costanza Maria; Calabró, Luana; Ventura, Valeria; Cutaia, Ornella; Chiarucci, Carla; Covre, Alessia; Garofalo, Cinzia; Pontén, Victor; Tallerico, Rossana; Frumento, Paolo; Micke, Patrick; Maio, Michele (2019-10-15). "NK- and T-cell subsets in malignant mesothelioma patients: Baseline pattern and changes in the context of anti-CTLA-4 therapy". International Journal of Cancer. 145 (8): 2238–2248. doi: 10.1002/ijc.32363 . ISSN   0020-7136. PMID   31018250.
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.