Basic Immunology And Serology

Fibrinogen is an important clotting factor because it plays a crucial role in the formation of blood clots. When there is tissue damage or injury, fibrinogen is converted into fibrin by the enzyme thrombin. Fibrin forms a mesh-like structure that helps in the clotting process by trapping platelets and other blood cells, forming a stable clot. This clot then prevents excessive bleeding and allows for the healing of the damaged tissue.

T lymphocytes undergo antigen-independent maturation in the thymus. The thymus is a specialized organ of the immune system located in the upper chest. It is responsible for the development and maturation of T lymphocytes, also known as T cells. T cells are a type of white blood cell that play a crucial role in the immune response. In the thymus, T cells undergo a process called positive and negative selection, where they learn to recognize self from non-self antigens. This maturation process is essential for the proper functioning of the immune system.

IgM is able to activate complement. Complement is a group of proteins that play a role in the immune response by promoting inflammation, attracting immune cells, and destroying pathogens. IgM is a type of antibody that is produced during the primary immune response. It can bind to antigens on the surface of pathogens and activate the complement system, leading to the destruction of the pathogen. IgA, IgD, and IgE do not have the ability to activate complement.

Rheumatoid arthritis is an autoimmune disease that causes pain and progressive destruction of the joints. It is characterized by symptoms such as weight loss, morning stiffness, and the presence of an antibody directed against IgG. This explanation fits the given description of the disease, making Rheumatoid arthritis the correct answer.

The zone at which antibody and antigen are at optimal concentration so that they form a large insoluble lattice together is called the equivalence zone. In this zone, the antibody and antigen molecules are present in equal amounts, allowing for the formation of a large lattice structure. This lattice formation is important for various immunological reactions, such as precipitation and agglutination. The equivalence zone is crucial for accurate and efficient immune responses.

Natural immunity refers to the ability of the body to resist infection through its normal physiological processes, such as the skin acting as a physical barrier, mucous membranes producing mucus to trap pathogens, and the immune system's innate response to destroy and eliminate pathogens. This type of immunity is present from birth and provides a general defense against a wide range of pathogens. Autoimmunity, acquired immunity, and alloimmunity are different types of immune responses that are not specifically related to the body's normal functions in resisting infection.

HLA (MHC) class I proteins are found on all nucleated cells. This is because these proteins play a crucial role in the immune system by presenting antigens to T cells, which helps in identifying infected or abnormal cells. Since all nucleated cells have the potential to be infected or abnormal, it is necessary for them to express HLA class I proteins to enable immune recognition and response. Therefore, HLA class I proteins are not limited to specific cell types like RBCs, B cells, macrophages, or stem cells, but are present on all nucleated cells.

Elevated levels of acute phase reactants indicate the presence of inflammation in the patient. However, the cause of the inflammation is unknown. This result suggests that there is an ongoing inflammatory response in the body, but further investigation is needed to determine the underlying cause of the inflammation.

Precipitation reactions occur when a soluble antibody combines with a soluble antigen. This reaction results in the formation of an insoluble complex called a precipitate. Soluble antigens are substances that can dissolve in a solution, and when they come into contact with soluble antibodies, they form a complex that is no longer soluble and can be observed as a precipitate. Cellular antigens, red blood cells, and radioactive antigens are not mentioned in the question and are therefore not involved in precipitation reactions.

All of the options listed can adversely affect an electrophoresis reaction. Decreasing the strength of the current can lead to slower migration of molecules, potentially causing inaccurate results. Changing the pH of the buffer can alter the charge and stability of the molecules being separated, affecting their migration. Increasing the strength of the current can generate excessive heat, leading to denaturation or degradation of the molecules. Therefore, all of these factors can have a negative impact on the electrophoresis reaction.

C3 is found in both the classic and alternative pathways of the complement system. It is a crucial component that plays a central role in the activation and amplification of the complement cascade. C3 is cleaved into C3a and C3b, where C3b binds to the surface of pathogens and opsonizes them for phagocytosis. This activation of C3 is a common step in both the classic and alternative pathways, making it the correct answer.

Universal precautions refer to a set of infection control practices that are used to prevent the transmission of bloodborne pathogens in healthcare settings. These precautions involve treating every specimen and patient as if they were infectious, regardless of their actual infection status. This approach ensures that healthcare workers take necessary precautions to prevent the spread of infections and protect themselves and others from potential harm. By assuming that all specimens are infectious, healthcare workers can consistently follow appropriate safety measures such as wearing gloves, masks, and other protective equipment, and properly handling and disposing of specimens to minimize the risk of transmission.

Postzone refers to a situation in which the antigen is present in excess compared to the antibody. In this scenario, the excess antigen can saturate all the available binding sites on the antibody, preventing the formation of antigen-antibody complexes. This results in a lack of visible reaction or false-negative results in diagnostic tests.

B cells undergo antigen-independent differentiation in the bone marrow. This is where B cells develop from hematopoietic stem cells and undergo a series of maturation processes, including rearrangement of immunoglobulin genes and expression of surface immunoglobulin receptors. Antigen-independent differentiation in the bone marrow is crucial for the generation of a diverse repertoire of B cells with different antigen specificities. Once mature, B cells leave the bone marrow and migrate to secondary lymphoid organs such as the spleen, lymph nodes, and Peyer's patches, where they can encounter antigens and undergo further activation and differentiation.

IgG and IgM are the immunoglobulins that help initiate the classic complement pathway. The classic complement pathway is activated by the binding of IgG or IgM antibodies to antigens on the surface of pathogens. This binding triggers a cascade of reactions that results in the activation of complement proteins and the formation of a membrane attack complex, leading to the destruction of the pathogen. IgA and IgD do not play a direct role in initiating the classic complement pathway.

Class II MHC antigens are necessary for antigen recognition by CD4-positive T-cells. CD4-positive T-cells are a type of immune cell that plays a crucial role in coordinating the immune response. These cells recognize antigens presented by MHC class II molecules on the surface of antigen-presenting cells. MHC class II molecules are primarily expressed on antigen-presenting cells such as dendritic cells, macrophages, and B cells. When a CD4-positive T-cell recognizes an antigen presented by MHC class II, it triggers an immune response to eliminate the antigen. Therefore, Class II MHC antigens are necessary for antigen recognition by CD4-positive T-cells.

Measurement of CRP levels could be useful in determining the risk of a heart attack because elevated levels of CRP in the blood indicate inflammation, which is a risk factor for heart disease. It can also be used to determine the flare-up of rheumatoid arthritis, as high CRP levels are associated with increased disease activity. Additionally, CRP levels can be measured to detect an inflammatory process in the body, as it is a marker of inflammation. Therefore, all of the given options are correct and CRP measurement can be useful for all of these purposes.

IgE is the correct answer because it is the immunoglobulin isotype involved in type I hypersensitivity reactions. IgE is responsible for allergic responses and triggers the release of histamine and other inflammatory mediators when bound to allergens. This leads to symptoms such as itching, swelling, and difficulty breathing commonly seen in allergic reactions like hay fever or anaphylaxis. IgA, IgG, and IgM are not typically involved in type I hypersensitivity reactions.

The chain of infection refers to the process by which infectious diseases are transmitted from one person to another. In this case, the staphylococcal infection is being passed between patients due to health-care workers not washing their hands. This represents a link in the chain of infection, as the infection is being transmitted through direct contact with contaminated hands.

Acquired immunity is characterized by the involvement of memory. This means that the immune system has the ability to recognize and remember specific pathogens that it has encountered before. When the body is exposed to a particular pathogen for the first time, the immune system mounts a response to eliminate it. However, during this initial encounter, the immune system also creates memory cells that "remember" the pathogen. If the body is exposed to the same pathogen again in the future, the immune system can mount a faster and more effective response due to the presence of these memory cells.

The target recognition molecule of the lectin pathway that initiates complement activation is Mannose-Binding Lectin. This molecule binds to carbohydrates on the surface of pathogens, such as bacteria or viruses, initiating the activation of the complement system. Once bound, Mannose-Binding Lectin recruits other complement proteins to the pathogen surface, leading to the formation of a membrane attack complex and ultimately the destruction of the pathogen. C1q, C4, and C5b6789 are all components of the classical pathway of complement activation, not the lectin pathway.

IgM is the first immunoglobulin to appear in the immune response and is the receptor for antigens on a mature B cell. It plays a crucial role in the primary immune response by binding to antigens and initiating the activation of B cells. IgM is a pentameric antibody that is primarily found in the bloodstream and lymph fluid, and it is particularly effective at neutralizing pathogens and activating complement.

In an immunologic immunoassay, the prozone refers to a situation where the antibody is present in excess compared to the antigen. This imbalance can lead to false-negative results as the excessive antibodies can prevent the formation of antigen-antibody complexes necessary for accurate detection.

The titer of the antibody is 32. This is because the highest dilution that does not show any visible agglutination is in the 1:64 tube. Therefore, the last dilution that showed agglutination is the 1:32 tube, indicating that the titer is 32.

Acute phase reactants are proteins that are produced by the liver in response to inflammation or infection. They are used as markers to monitor the presence and severity of these conditions, but they are not specific enough to diagnose a specific disease. Therefore, the correct answer is "Used to diagnose a specific disease."

Haptoglobin is an acute phase protein that binds to free hemoglobin in the blood. When red blood cells are damaged or destroyed, hemoglobin is released into the bloodstream. Haptoglobin binds to this free hemoglobin, preventing its toxic effects and facilitating its removal by macrophages. This helps to prevent oxidative damage and kidney injury that can occur due to the presence of free hemoglobin. Therefore, the function of haptoglobin is to bind hemoglobin.

Natural immunity, also known as innate immunity, is a non-specific defense mechanism that is present in the body from birth. It relies on the normal functions of the body, such as the skin and mucous membranes, to provide a barrier against pathogens. This type of immunity does not involve memory or lymphocytes, and it is not specific to a particular pathogen. Instead, it provides a general defense against a wide range of potential threats.

HLA (MHC) class I antigens are found on all nucleated cells. This means that these antigens are present on the surface of almost all cells in the body except for red blood cells. They play a crucial role in the immune system by presenting antigens to cytotoxic T cells, which then initiate an immune response against infected or abnormal cells. This widespread distribution of HLA class I antigens allows for efficient detection and elimination of potentially harmful cells throughout the body.

Hemagglutination is a serological test that uses red blood cells coated with exogenous antigens to detect patient antibodies against the antigen. In this test, if the patient has antibodies against the antigen, they will cause the red blood cells to clump together or agglutinate. This agglutination can be visually observed, indicating the presence of antibodies. Hemagglutination is commonly used for blood typing and detecting certain viral infections.

To make a 1:20 dilution, the ratio of serum to the final volume should be 1:20. Since the final volume is 5 mL, we can calculate the amount of serum needed by multiplying 5 mL by the ratio (1/20). This gives us 0.25 mL of serum needed to make the dilution.

Autoimmunity occurs when the immune system mistakenly attacks the body's own cells and tissues. The causes of autoimmunity can include factors such as inheritance of certain HLA antigens, molecular mimicry (where the immune system mistakenly identifies self-antigens as foreign), and polyclonal B cell activation (which can lead to the production of autoantibodies). However, normal antibody production is not a reason for autoimmunity as it is a normal immune response to protect the body against infections and foreign substances.

C-reactive protein (CRP) acts as an opsonin, which means it enhances the immune system's ability to recognize and eliminate foreign particles, such as bacteria and viruses. By binding to these pathogens, CRP facilitates their recognition and uptake by immune cells, promoting their destruction. This function of CRP is crucial in the body's defense against infections and inflammation.

In the latex agglutination slide test for CRP (C-reactive protein), latex particles are coated with anti-CRP antibodies. When a sample containing CRP is added to the latex particles, the CRP molecules bind to the anti-CRP antibodies on the latex particles, causing agglutination or clumping of the latex particles. This reaction is specific to CRP and indicates the presence of CRP in the sample.

Heterophile antigens are characterized as found in unrelated plants or animals but cross-react with the same antibody. This means that these antigens can be present in different species but can still trigger an immune response in the same way, as they are recognized by the same antibodies. This cross-reactivity allows for the development of diagnostic tests, such as the monospot test for infectious mononucleosis, where antibodies produced against one heterophile antigen can also react with a similar antigen from another species.

The given description of the immunoassay involves the binding of patient antibodies to an antigen on a solid support, followed by the addition of enzyme-labeled anti-immunoglobulin antibodies. This is a characteristic of an ELISA (Enzyme-Linked Immunosorbent Assay), where the enzyme-labeled antibodies are used to detect the presence or quantity of the patient antibodies.

The correct answer is Agglutination. In agglutination assays, the antigen is bound to a larger carrier, such as latex beads or red blood cells, and the antibody is soluble. When the antibody binds to the antigen, it forms visible clumps or aggregates that can be detected macroscopically. This assay is commonly used in blood typing and diagnosing certain infections.

Coombs' reagent is used to enhance agglutination with IgG coated red blood cells. This reagent contains antibodies that specifically bind to IgG antibodies on the surface of red blood cells. When Coombs' reagent is added to a sample containing IgG coated red blood cells, it causes the cells to clump together, or agglutinate. This reaction is useful in various laboratory tests, such as the Coombs' test, which is used to detect and diagnose conditions involving immune-mediated destruction of red blood cells, such as autoimmune hemolytic anemia.

T cells undergo maturation and selection in the cortex of the thymus, followed by further maturation and selection in the medulla. Once they have completed this process, mature T cells are released into the secondary lymphoid organs to carry out their immune functions. The correct answer describes the correct sequence of events in the maturation of T cells in the thymus.

Competitive binding assays involve a limited number of binding sites being present. In this type of assay, a labeled analyte competes with an unlabeled analyte (patient antigen) for binding to these limited binding sites. The concentration of the patient antigen is directly proportional to the label detected because as the concentration of patient antigen increases, more of it competes with the labeled analyte for binding to the limited binding sites, resulting in less label being detected. Therefore, the answer is that a limited number of binding sites are present.

In this type of assay, a serological reaction is set up using soluble antigen and antibody. When the antigen and antibody combine, they form an insoluble complex, which can be detected macroscopically. This process is known as precipitation.

C3b can activate the alternative complement pathways. C3b is a component of the complement system that plays a crucial role in the activation of the alternative pathway. When C3b binds to a foreign surface, it recruits other complement proteins and initiates a cascade of reactions that lead to the formation of a membrane attack complex, which can destroy the target cell. Therefore, C3b is an important activator of the alternative complement pathways.

Fluorescence is used to determine the expression of cell surface markers in a flow cytometer. This technique involves labeling specific antibodies with fluorescent dyes, which bind to the cell surface markers of interest. When the labeled cells pass through the flow cytometer, they are excited by a laser or other light source, causing the fluorescent dye to emit light at a specific wavelength. The emitted light is then detected by the flow cytometer, allowing for the quantification and analysis of the cell surface markers.

When IgM on the surface of an immature B cell binds to a self-antigen, the process of apoptosis can occur. Apoptosis is a programmed cell death mechanism that eliminates cells that are potentially harmful or dysfunctional. In this case, when the immature B cell recognizes a self-antigen, it is considered as potentially harmful to the body. To prevent any autoimmune reactions, the B cell undergoes apoptosis, ensuring the removal of the self-reactive cell.

Type I hypersensitivity response is an immediate allergic reaction mediated by the release of histamine and other inflammatory mediators from mast cells and basophils. This response is primarily involved in protecting against parasites. When parasites invade the body, the immune system triggers a type I hypersensitivity response to eliminate them. This response causes symptoms such as itching, redness, and swelling, which are aimed at expelling or neutralizing the parasites. In contrast, type I hypersensitivity is not typically involved in protection against viruses, bacteria, or fungi, which are usually targeted by other immune mechanisms.

MHC class I and class II molecules are both involved in antigen recognition and are members of the immunoglobulin superfamily. They are also expressed codominantly, meaning that both alleles of the gene are expressed. However, they are not expressed constitutively on all nucleated cells. MHC class I molecules are expressed on most nucleated cells, while MHC class II molecules are primarily expressed on antigen-presenting cells.

An immature T cell co-expresses CD4 and CD8, which means it has both CD4 and CD8 proteins on its surface. This is different from a mature T cell, which only expresses either CD4 or CD8. The co-expression of CD4 and CD8 on an immature T cell is important for its development and selection in the thymus. Once the T cell matures, it will undergo a process called positive selection, where it will only express either CD4 or CD8, depending on its function as a helper or cytotoxic T cell.

Immunoelectrophoresis involves the separation of proteins by electrophoresis followed by the diffusion of antibodies from wells cut in the gel. This technique allows for the identification and quantification of specific proteins based on their electrophoretic mobility and reaction with antibodies. It is commonly used in clinical laboratories for the diagnosis and monitoring of various diseases, such as multiple myeloma.

When 0.5 mL of serum is added to 1.5 mL of diluent, the total volume becomes 0.5 mL + 1.5 mL = 2 mL.

To find the dilution ratio, we compare the volume of the serum to the total volume of the solution:

Dilution ratio = volume of serum : total volume Dilution ratio = 0.5 mL : 2 mL

To simplify this ratio, divide both parts by 0.5:

0.5 / 0.5 : 2 / 0.5 = 1 : 4

Therefore, this represents a 1:4 dilution.

In the slide agglutination test for lupus, the presence of Anti-DNP antibodies is detected. DNP stands for dinitrophenol, which is a hapten that is commonly used to simulate the behavior of nucleic acids in the test. The presence of Anti-DNP antibodies indicates an autoimmune reaction against nucleic acids, which is characteristic of lupus. Therefore, Anti-DNP is the correct answer for this question.

Edward Jenner's discovery that cowpox generated immunity against smallpox is based on the principle of cross-immunity. Cross-immunity refers to the phenomenon where immunity to one disease provides protection against another related disease. In this case, Jenner observed that individuals who had been infected with cowpox, a milder disease, were also protected against smallpox, a more severe and deadly disease. This discovery led to the development of the smallpox vaccine and marked a major breakthrough in the field of immunology.