20.3 Agglutination Assays
3 min read•june 18, 2024
assays are powerful tools for detecting specific antigens or antibodies in samples. They rely on the clumping of cells or particles when antibodies bind to matching antigens. These tests are widely used in , disease diagnosis, and bacterial identification.
Blood typing through agglutination is crucial for safe transfusions. It determines and by mixing red blood cells with specific antibodies. ensures compatibility between donor and recipient blood, preventing potentially life-threatening reactions.
Agglutination Assays
Direct vs indirect agglutination
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- involves antibodies binding directly to antigens on the surface of cells or particles (bacteria, red blood cells) used to detect the presence of specific antigens in a sample
- Blood typing determines ABO and by mixing red blood cells with antibodies specific to A, B, and D antigens
- Bacterial identification groups Streptococcus species based on specific cell wall antigens
- involves antibodies binding to soluble antigens, which then cross-link particles or cells (, red blood cells) used to detect the presence of specific antibodies in a sample
- diagnoses by detecting antibodies against Salmonella typhi antigens
- test detects in rheumatoid arthritis that agglutinate -coated particles
- can be determined by serial dilutions of the sample to find the highest dilution that still produces visible agglutination
Applications of hemagglutination
- involves the agglutination of red blood cells (RBCs) in the presence of specific antibodies or antigens
- Viral occurs when viruses (influenza) have surface proteins that bind to receptors on RBCs causing agglutination
- test detects antibodies against these viruses in a patient's serum that inhibit agglutination
- Bacterial hemagglutination occurs when bacteria () produce that bind to RBCs causing agglutination
- Indirect hemagglutination test detects antibodies against these bacteria in a patient's serum that agglutinate bacteria-coated RBCs
Blood Typing and Transfusion
Blood typing through agglutination
- ABO blood typing determines blood type based on the presence or absence of A and B antigens on RBCs and anti-A and anti-B antibodies in the serum
- Agglutination occurs when the corresponding antigen and antibody are mixed
- Four blood types: A (A antigen), B (B antigen), AB (both A and B antigens), O (neither antigen)
- Rh blood typing determines Rh status based on the presence or absence of the Rh factor (D antigen) on RBCs
- Agglutination occurs when Rh-positive RBCs are mixed with anti-D antibodies
- Rh-positive individuals have the D antigen, Rh-negative individuals lack the D antigen
Cross-matching for blood transfusions
- Cross-matching ensures compatibility between donor and recipient blood to prevent reactions
- Steps in cross-matching:
- ABO and Rh typing of both donor and recipient blood
- Screening recipient serum for the presence of unexpected antibodies ()
- Mixing recipient serum with donor RBCs to check for agglutination ()
- Agglutination indicates incompatible donor blood that cannot be used
- No agglutination indicates compatible donor blood that can be safely transfused
- Agglutination in cross-matching indicates the presence of antibodies in the recipient's serum that can react with antigens on the donor's RBCs
- Transfusing incompatible blood can lead to severe transfusion reactions (hemolytic reactions, acute kidney injury)
- can occur when antibodies recognize similar epitopes on different antigens, potentially leading to false-positive results
Additional Considerations in Agglutination Assays
- : A phenomenon where excess antibodies in a sample can interfere with agglutination, leading to false-negative results in high-concentration samples
- : Antibodies that cause agglutination at low temperatures, which can affect blood typing and transfusion procedures
- : A modification of the agglutination assay where complement proteins are used to enhance the sensitivity of the test, particularly useful in detecting certain bacterial and viral infections
Key Terms to Review (71)
ABO: ABO is a system that classifies human blood into four main groups based on the presence or absence of specific antigens on the surface of red blood cells. This system is a crucial component in agglutination assays, which are used to determine blood type and compatibility for transfusions and organ transplants.
Acute phase: The acute phase is the immediate response of the immune system to infection or injury, characterized by the rapid production of proteins and activation of immune cells. It aims to contain and eliminate pathogens while signaling further immune responses.
Adhesins: Adhesins are surface structures on pathogens that allow them to adhere to host cells. They play a crucial role in the initial stages of microbial infection.
Adhesins: Adhesins are specialized surface molecules found on the cells of many pathogens that enable them to attach to and infect host cells. They act as the 'sticky' components that facilitate the initial stages of pathogenesis by allowing the pathogen to bind to and invade the host's tissues.
Agglutination: Agglutination is the process by which antibodies bind to and cause the clumping or aggregation of antigens, such as bacteria or other foreign particles, into larger visible complexes called agglutinates. This phenomenon is a key concept in understanding antigen-antibody interactions and is widely used in various immunological assays and diagnostic techniques.
Antibody screen: An antibody screen is a laboratory test used to detect antibodies in a patient's blood. It is commonly performed to identify unexpected antibodies that might cause reactions during blood transfusions or pregnancies.
Antibody Titer: An antibody titer is a measurement of the concentration or amount of antibodies present in a person's blood. It is a quantitative assessment of the body's immune response to a specific antigen, providing information about the level of antibodies produced.
Antigen-Antibody Complexes: Antigen-antibody complexes are the physical interactions that occur between an antigen, a foreign substance that can induce an immune response, and an antibody, a protein produced by the immune system to recognize and neutralize that antigen. These complexes are central to the body's adaptive immune response and serve as the basis for various immunological techniques, including agglutination assays.
Autoantibodies: Autoantibodies are antibodies produced by the body's own immune system that mistakenly target and attack the body's healthy cells and tissues, leading to autoimmune disorders. These abnormal antibodies are a key feature in understanding the pathogenesis of various autoimmune diseases as well as their detection and diagnosis through agglutination assays.
Autoimmune hemolytic anemia: Autoimmune hemolytic anemia (AIHA) is a condition where the immune system mistakenly attacks and destroys red blood cells, leading to anemia. This results in symptoms like fatigue, pallor, and shortness of breath.
Avery: Avery refers to Oswald Avery, a scientist whose experiments in the 1940s demonstrated that DNA is the substance that causes bacterial transformation. His work was pivotal in identifying DNA as the molecule responsible for heredity.
Blood types: Blood types are classifications of blood based on the presence or absence of specific antigens on the surface of red blood cells. The main blood group systems are ABO and Rh.
Blood Typing: Blood typing is a laboratory test that determines an individual's blood group based on the presence or absence of certain antigens on the surface of red blood cells. It is a crucial step in blood transfusions and organ transplantation to ensure compatibility and prevent adverse reactions.
Cold Agglutinins: Cold agglutinins are autoantibodies that react with antigens on the surface of red blood cells at lower temperatures, typically below 37°C (98.6°F). This phenomenon is known as cold agglutination, and it can lead to the clumping or agglutination of red blood cells, which is an important concept in the context of agglutination assays.
Complement Fixation: Complement fixation is an immunological assay that measures the ability of antibodies in a sample to activate the complement system, a group of proteins that help eliminate pathogens. It is a key technique used in the context of agglutination assays to detect and quantify specific antibodies or antigens.
Convalescent phase: The convalescent phase is the period during which a patient is recovering from an infection and their symptoms are decreasing. It is marked by the development of specific antibodies against the pathogen.
Cross-match: Cross-match is a laboratory test used to ensure compatibility between donor and recipient blood before transfusion. It involves mixing small samples of the donor's and recipient's blood to check for agglutination or hemolysis.
Cross-matching: Cross-matching is a critical step in blood typing and transfusion medicine, where a patient's blood is tested against potential donor blood to ensure compatibility and prevent adverse reactions. It involves a series of tests to identify any antibodies or antigens that could lead to an incompatible blood match.
Cross-reactivity: Cross-reactivity occurs when an antibody directed against one specific antigen also reacts with a different, but structurally similar, antigen. This phenomenon can have significant implications in diagnostic tests and immune responses.
Cross-reactivity: Cross-reactivity refers to the ability of an antibody or antigen to bind to multiple, structurally similar targets, leading to potential false-positive or false-negative results in various immunological assays and diagnostic tests.
Direct Agglutination: Direct agglutination is a serological test used to detect the presence of specific antibodies in a sample by observing the clumping or agglutination of antigen-coated particles. This technique is a fundamental principle in agglutination assays, which are widely employed in various diagnostic and research applications.
Direct agglutination assay: A direct agglutination assay is a laboratory technique used to detect antibodies or antigens in a sample by mixing it with particles that will clump together if the target molecule is present. This method is commonly used for diagnosing infections and blood typing.
Direct antihuman globulin test (DAT): The Direct Antihuman Globulin Test (DAT), also known as the direct Coombs test, detects antibodies or complement proteins attached to the surface of red blood cells. It is used to diagnose conditions like autoimmune hemolytic anemia and hemolytic disease of the newborn.
Direct Coombs’ test: The direct Coombs’ test detects antibodies that are attached to the surface of red blood cells. It is used to diagnose conditions such as autoimmune hemolytic anemia.
Direct hemagglutination assays: Direct hemagglutination assays are laboratory techniques used to detect the presence of antibodies or antigens in a sample by observing the agglutination (clumping) of red blood cells. This method is commonly employed to diagnose infections and monitor immune responses.
Dochez: The Dochez agglutination assay is a laboratory technique used to detect the presence of specific antibodies or antigens in a sample by observing clumping reactions. It is named after American bacteriologist and immunologist, Alfred F. Dochez.
Epstein-Barr virus: Epstein-Barr virus (EBV) is a herpesvirus that primarily infects B cells and epithelial cells, causing mononucleosis. It is associated with several cancers, including Burkitt's lymphoma and nasopharyngeal carcinoma.
Hemagglutination: Hemagglutination is the clumping of red blood cells due to the presence of a virus or antibodies. It is commonly used in laboratory assays to detect viral infections and determine antibody levels.
Hemagglutination: Hemagglutination is the agglutination or clumping of red blood cells, which can occur due to the interaction between certain molecules, such as viruses or antibodies, and receptors on the surface of red blood cells. This process is an important tool in the isolation, culture, and identification of viruses, as well as in various agglutination assays.
Hemagglutination Inhibition: Hemagglutination inhibition is an assay used to detect and quantify antibodies in a sample by their ability to inhibit the agglutination of red blood cells (RBCs) by a specific antigen. It is a widely used technique in immunology and virology to identify and measure the presence of antibodies against various pathogens.
Hemagglutinin: Hemagglutinin is a glycoprotein found on the surface of certain viruses, such as the influenza virus, that causes red blood cells to clump together. It plays a crucial role in the initial stages of viral infection by binding to host cell receptors.
Hemolytic disease of the newborn: Hemolytic disease of the newborn (HDN) is a condition where the immune system of an Rh-negative mother produces antibodies that attack the red blood cells of her Rh-positive baby. This leads to hemolysis and significant health issues for the infant.
Hemolytic transfusion reactions: Hemolytic transfusion reactions (HTRs) are immune responses that occur when incompatible blood is transfused, leading to the destruction of red blood cells. This can result in serious complications such as kidney failure, shock, and even death.
IgG: IgG, or Immunoglobulin G, is the most abundant type of antibody found in the human body. It plays a crucial role in the adaptive immune response, contributing to pathogen recognition, phagocytosis, and the regulation of humoral immunity.
Immunological: Immunological refers to the processes, responses, and mechanisms related to the immune system. It encompasses the body's ability to recognize, defend against, and respond to foreign or harmful substances, such as pathogens, toxins, and diseased cells, in order to maintain homeostasis and health.
Indirect Agglutination: Indirect agglutination is a serological technique used to detect the presence of specific antibodies in a sample by using an antigen-coated particle as a detection agent. This method relies on the ability of the target antibodies to bind to the antigen, forming a visible agglutination or clumping of the particles, which indicates a positive result.
Indirect agglutination assay: An indirect agglutination assay is a laboratory technique used to detect antibodies or antigens by their ability to cause agglutination, using particles like latex beads coated with specific antigens or antibodies. This method enhances the visibility of the reaction and is commonly used in diagnosing infectious diseases.
Indirect antiglobulin test (IAT): The indirect antiglobulin test (IAT) is a laboratory technique used to detect antibodies in a patient's serum that are capable of binding to red blood cells. It is commonly used in blood compatibility testing and antibody screening.
Indirect Coombs’ test: The indirect Coombs' test is a laboratory assay used to detect antibodies against red blood cells (RBCs) in a patient's serum. It is commonly used in prenatal testing and before blood transfusions.
Jaundice: Jaundice is a medical condition characterized by the yellowing of the skin and eyes due to elevated bilirubin levels in the blood. It often indicates underlying issues with the liver, bile ducts, or red blood cells.
Lancefield: Lancefield classification is a system used to categorize certain types of bacteria, particularly streptococci, based on the carbohydrate composition of bacterial antigens found on their cell walls. This system is crucial for identifying pathogenic species and understanding their role in infections.
Latex Agglutination: Latex agglutination is a type of agglutination assay used to detect the presence of specific antibodies or antigens in a sample. It involves the use of latex particles coated with an antigen or antibody that will bind to the corresponding target in the sample, causing the latex particles to clump together or agglutinate, indicating a positive result.
Latex beads: Latex beads are small, spherical particles made from polystyrene or other polymers used in various laboratory assays. They can be coated with specific antigens or antibodies to detect the presence of complementary molecules.
Latex fixation assay: A latex fixation assay is a laboratory method used to detect specific antibodies or antigens in a sample by using latex beads coated with the target molecule. The presence of agglutination (clumping) indicates a positive reaction.
M protein: M protein is a virulence factor found on the surface of certain bacteria, notably Streptococcus pyogenes. It plays a crucial role in evading the host immune response by inhibiting phagocytosis.
Microtiter plate: A microtiter plate is a flat plate with multiple wells used as small test tubes in laboratory experiments. It is commonly used for assays like agglutination to analyze immune responses.
Mumps: Mumps is a contagious viral infection characterized by the swelling of the parotid glands, which are salivary glands located near the ears. It can also cause complications in other parts of the body, including the nervous system and reproductive organs.
Mycoplasma pneumonia: Mycoplasma pneumonia is a type of bacterial infection that primarily affects the respiratory tract, leading to atypical pneumonia. It is caused by the bacterium Mycoplasma pneumoniae, which lacks a cell wall.
Mycoplasma pneumoniae: Mycoplasma pneumoniae is a species of bacterium that is a common cause of atypical or 'walking' pneumonia, particularly in older children and young adults. It is a small, pleomorphic, and slow-growing bacterium that lacks a cell wall, making it resistant to many common antibiotics.
Neuraminidase: Neuraminidase is an enzyme found on the surface of influenza viruses that helps the virus release from the host cell after replication. It is a target for antiviral drugs like oseltamivir.
Precipitin: A precipitin is an antibody that binds to its corresponding antigen, forming a visible precipitate. This reaction is a key principle underlying agglutination assays, which are used to detect and identify specific antigens or antibodies in a sample.
Prozone Effect: The prozone effect refers to a phenomenon in antigen-antibody interactions where an excess of antigen can actually inhibit the detection or visualization of the antigen-antibody complex. This effect is particularly relevant in the context of detecting antigen-antibody complexes and agglutination assays.
Rh: Rh, or Rhesus factor, is a protein found on the surface of red blood cells. It is an important consideration in blood typing and transfusion medicine, as well as during pregnancy and childbirth. The presence or absence of the Rh factor is a key factor in agglutination assays, which are used to determine blood type and compatibility.
Rh blood groups: Rh blood groups are classifications of blood based on the presence or absence of the Rh antigen, also known as the Rh factor, on the surface of red blood cells. The most significant antigen in this group is the D antigen.
Rheumatoid Factor: Rheumatoid factor is an autoantibody that is commonly found in the blood of individuals with rheumatoid arthritis, an autoimmune disorder characterized by chronic inflammation of the joints. This antibody targets the Fc portion of the body's own immunoglobulin G (IgG) molecules, leading to the formation of immune complexes that contribute to the inflammatory response.
Rheumatoid factor (RF): Rheumatoid Factor (RF) is an autoantibody found in the blood that targets the Fc region of IgG antibodies. It is commonly used as a marker in the diagnosis of rheumatoid arthritis and other autoimmune diseases.
Salmonella enterica subspecies typhi: Salmonella enterica subspecies typhi is a pathogenic bacterium responsible for typhoid fever in humans. It is known for its role in systemic infections and its ability to evade the host immune response.
Serial dilution: Serial dilution is a stepwise dilution of a substance in solution, often used to reduce a dense culture of cells to a more usable concentration. It is frequently employed in microbiology to estimate the number of organisms present in a sample.
Seroconversion: Seroconversion is the period during which a specific antibody develops and becomes detectable in the blood. It indicates a change from seronegative (absence of antibodies) to seropositive (presence of antibodies).
Serological: Serological refers to the analysis and study of serum, the liquid portion of blood that contains antibodies and other proteins. This term is particularly relevant in the context of detecting antigen-antibody complexes and agglutination assays, which are important techniques in immunology and diagnostic testing.
Serovars: Serovars are distinct variations within a species of bacteria or viruses, identified by differences in their surface antigens. They are used to classify microorganisms for epidemiological studies and disease tracking.
Strep throat: Strep throat is a bacterial infection caused by Streptococcus pyogenes, characterized by inflammation and pain in the throat. It is highly contagious and spreads through respiratory droplets.
Streptococci: Streptococci are a genus of Gram-positive bacteria that form chains or pairs and are known for causing various infections in humans. They are classified based on their hemolytic properties and carbohydrate antigens on their cell walls.
Syphilis: Syphilis is a sexually transmitted infection caused by the bacterium Treponema pallidum. It progresses through distinct stages and can lead to serious health complications if left untreated.
Titer: Titer refers to the concentration of a substance in a solution, often used to measure the level of antibodies or antigens in a serum. It is determined by serially diluting the sample and identifying the highest dilution at which activity is still detectable.
Transfusion: Transfusion is the process of transferring blood or blood products from one person into another's circulatory system. It is crucial in managing blood loss and treating various medical conditions.
Transfusion: Transfusion is the process of transferring blood or blood components from one individual (the donor) to another (the recipient). It is a critical medical procedure used to replace lost blood, provide missing blood components, or treat various blood-related disorders.
Typhoid fever: Typhoid fever is a serious bacterial infection caused by the protoebacterium Salmonella enterica serotype Typhi. It spreads through contaminated food and water, leading to high fever, abdominal pain, and other systemic symptoms.
Viral hemagglutination inhibition assay: A viral hemagglutination inhibition assay is a laboratory technique used to measure the ability of antibodies to prevent viruses from agglutinating red blood cells. It is commonly employed to quantify immune responses and detect specific viral infections.
Widal test: The Widal test is a serological assay used to diagnose enteric fever, particularly typhoid fever, by detecting agglutinating antibodies against Salmonella antigens in the patient's serum.
Widal Test: The Widal test is a serological test used to diagnose typhoid fever, a life-threatening infectious disease caused by the bacterium Salmonella Typhi. It detects the presence of antibodies produced by the body in response to the Salmonella Typhi infection, allowing for the diagnosis of the disease.