Immunopathology and Immune Response Mechanisms

What is the first step of humoral immunity?

Antigen Recognition, where B cells encounter antigens on pathogens.

What role does Major Histocompatibility Complex II (MHC II) play in humoral immunity?

It presents fragments of internalized antigens on the surface of B cells.

How are B cells activated in humoral immunity?

Helper T cells recognize the antigen-MHC II complex and release cytokines.

What occurs during clonal selection of B cells?

Activated B cells divide and produce identical clones, differentiating into plasma cells and memory B cells.

What is the function of plasma cells in humoral immunity?

Plasma cells produce antibodies that specifically bind to the initiating antigen.

What happens to antibodies produced by plasma cells?

They are released into the bloodstream to bind to antigens, marking them for destruction.

List the four functions of antibodies in humoral immunity.

1. Neutralization 2. Opsonization 3. Complement Activation 4. Agglutination.

What are memory B cells and their significance?

They persist in the body and enable a faster response upon re-exposure to the same pathogen.

How does long-term immune memory work in humoral immunity?

Memory B cells quickly differentiate into plasma cells upon re-encountering the same antigen, producing a rapid antibody response.

What is the first step of cellular immunity?

Antigen Recognition, where antigen-presenting cells (APCs) process and present antigens.

What are antigen-presenting cells (APCs)?

Cells like dendritic cells, macrophages, and B cells that present antigen fragments using MHC molecules.

What is required for full T cell activation?

Co-stimulatory signals from APCs and cytokines like Interleukin-1 (IL-1).

What happens during clonal expansion of T cells?

Activated helper T cells proliferate to produce a large number of identical T cells specific to the antigen.

What are the specialized subsets of helper T cells?

Th1, Th2, Th17, and regulatory T cells (Tregs), differentiated based on the cytokine environment.

How do cytotoxic T cells (CTLs) recognize infected cells?

They recognize antigens presented on MHC class I molecules of infected cells.

What stimulates the activation and differentiation of cytotoxic T cells?

Cytokines like Interleukin-2 (IL-2) produced by helper T cells.

What is the cytotoxic activity of activated cytotoxic T cells?

They release perforin and granzymes to induce apoptosis in infected cells.

What are memory T cells and their role in immunity?

Memory T cells are activated T cells that provide long-term immunity against specific pathogens, responding more rapidly and efficiently upon re-exposure to the same antigen.

What is the function of Regulatory T Cells (Tregs)?

Tregs suppress excessive immune responses to prevent autoimmune reactions and maintain immune system balance.

What happens to effector T cells after an infection is cleared?

Most effector T cells undergo apoptosis, while memory T cells persist to provide rapid responses upon subsequent encounters with the same pathogen.

What is cellular immunity and how does it work with humoral immunity?

Cellular immunity protects against intracellular threats and works in concert with humoral immunity to provide comprehensive defense against a wide range of pathogens.

What role do antigen-receptor interactions play in the immune system?

Antigen-receptor interactions are crucial for the immune system's ability to recognize and respond to foreign substances, distinguishing between self and non-self.

What are antigens and receptors in the context of the immune system?

Antigens are molecules that induce an immune response, while receptors are proteins that specifically bind to these antigens.

What are B Cell Receptor (BCR) interactions?

BCR interactions involve B cells recognizing and binding to specific antigens, triggering B cell activation, antibody production, and memory B cell formation.

What triggers B cell activation?

BCR engagement with an antigen triggers B cell activation, leading to antibody production and memory B cell formation.

What are T Cell Receptor (TCR) interactions?

TCR interactions involve T cells recognizing peptide antigens presented on the surface of infected or abnormal cells.

How do TCRs recognize antigens?

TCRs recognize antigens presented by major histocompatibility complex (MHC) molecules on the cell surface.

What are the two main types of T cells?

The two main types of T cells are CD4+ T cells (helper T cells) and CD8+ T cells (cytotoxic T cells).

How do CD4+ and CD8+ T cells differ in antigen recognition?

CD4+ T cells recognize antigens presented by MHC class II molecules, while CD8+ T cells recognize antigens presented by MHC class I molecules.

Why is binding specificity important in BCR and TCR interactions?

Binding specificity is crucial because it allows the receptors to recognize a wide range of antigens, enabling targeted immune responses.

What is the role of antibodies in the immune response?

Antibodies are proteins produced by B cells that recognize and neutralize specific antigens, marking pathogens for destruction by other immune cells.

How do vaccines confer specific immunity?

Vaccines introduce antigens that trigger an immune response, activating immune cells like B cells and T cells, leading to antibody production.

What components can vaccines contain to trigger an immune response?

Vaccines can contain proteins, sugars, or other components specific to the pathogen.

What happens when a person is vaccinated?

The immune system recognizes the antigens in the vaccine as foreign and mounts an immune response.

What is the significance of memory T cells in vaccination?

Memory T cells persist after vaccination, allowing for rapid and enhanced responses upon future encounters with the pathogen.

What is the relationship between cellular immunity and humoral immunity?

Cellular immunity and humoral immunity work together to provide a comprehensive defense against a wide range of pathogens.

What is the role of antigen presentation in T cell activation?

Antigen presentation by MHC molecules is essential for T cell activation, allowing TCRs to recognize and respond to specific antigens.

How do antigen-receptor interactions contribute to adaptive immunity?

They enable the immune system to mount targeted and effective responses against a wide array of pathogens.

What is the outcome of successful BCR engagement with an antigen?

Successful BCR engagement leads to B cell activation, antibody production, and the formation of memory B cells.

What is the importance of the immune system distinguishing between self and non-self?

This distinction allows the immune system to target and eliminate harmful invaders while avoiding attacks on the body's own cells.

What are memory cells and their role in the immune system?

Memory B cells and T cells are formed after the initial immune response, allowing the immune system to quickly recognize and respond to a previously encountered pathogen.

How do memory cells contribute to long-term immunity?

The presence of memory cells enables the immune system to respond quickly and effectively to future encounters with the same pathogen, preventing or reducing disease severity.

What is the role of vaccines in conferring specific immunity?

Vaccines help control and prevent infectious diseases by stimulating the immune system to produce memory cells, leading to long-term immunity.

What are some diseases that vaccines have helped to control or eradicate?

Vaccines have been instrumental in controlling diseases such as polio, measles, mumps, rubella, influenza, and hepatitis.

Why might vaccines not confer lifelong immunity?

While vaccines are effective, they may not provide lifelong immunity for all individuals, necessitating booster shots to enhance and prolong immunity.

What is the importance of regular vaccination efforts?

Regular vaccination is critical for maintaining community immunity and preventing the spread of infectious diseases.

What is immune hypersensitivity?

Immune hypersensitivity refers to exaggerated or inappropriate immune responses to antigens.

How many main types of immune hypersensitivity reactions are there?

There are four main types of immune hypersensitivity reactions: Types I, II, III, and IV.

What characterizes Type I hypersensitivity?

Type I hypersensitivity is mediated by IgE antibodies and results in rapid responses, such as asthma and allergies.

What is Type II hypersensitivity and its mechanism?

Type II hypersensitivity is cytotoxic and mediated by IgM or IgG antibodies that target antigens on cell surfaces, leading to reactions like Rh incompatibility.

What occurs during Type III hypersensitivity?

Type III hypersensitivity involves immune complexes that deposit in tissues, triggering inflammation and damage to blood vessels and organs.

What is an example of a Type IV hypersensitivity reaction?

Contact dermatitis caused by poison ivy is an example of Type IV hypersensitivity.

What is the timing of a Type I hypersensitivity reaction?

Type I hypersensitivity reactions occur rapidly, within minutes of exposure.

How long does it take for Type II hypersensitivity reactions to occur?

Type II hypersensitivity reactions typically occur within hours to days.

When do Type III hypersensitivity reactions generally manifest?

Type III hypersensitivity reactions generally occur hours to days after exposure.

What is the timing for Type IV hypersensitivity reactions?

Type IV hypersensitivity reactions are delayed, appearing 24 hours or more after exposure.

What can happen if kidneys are damaged by a Type III hypersensitivity reaction?

If kidneys are damaged by a Type III hypersensitivity reaction, dialysis may be required.

What is the role of epinephrine in severe allergic reactions?

Epinephrine counteracts severe drops in blood pressure that can result from life-threatening allergic reactions.

What is an example of a harmful immune response?

A bee-sting allergy is an example of an immune response that is harmful to the host rather than protective.

What happens during a hemolytic transfusion reaction (Type II hypersensitivity)?

In a hemolytic transfusion reaction, anti-A antibodies in a Type B recipient bind to Type A donor red blood cells, leading to their destruction.

What triggers the sensitization in Type IV hypersensitivity?

The first exposure to a hapten antigen, like poison ivy, does not cause a reaction but sensitizes helper T cells for future exposures.

What is the significance of booster shots in vaccination?

Booster shots may be recommended to enhance and prolong immunity, especially against emerging variants or waning immunity.

What happens to memory helper T cells upon secondary exposure to an allergen?

They become reactivated and produce inflammatory cytokines that stimulate macrophages and cytotoxic T cells, inducing an inflammatory lesion.

What can occur if an inflammatory lesion persists at the site of allergen exposure?

It can inflict significant tissue damage.

What are the consequences of a weakened immune system?

Increased susceptibility to infections, which can be more severe and prolonged.

What are autoimmune diseases?

Conditions where the immune system mistakenly attacks the body's own cells, examples include rheumatoid arthritis, lupus, multiple sclerosis, and type 1 diabetes.

What is a common characteristic of systemic lupus erythematosus?

Autoimmunity to the individual's own DNA and/or proteins, often presenting with a butterfly rash.

What are immunodeficiency disorders?

Conditions characterized by a weakened or absent immune response, making individuals vulnerable to frequent and severe infections.

What can cause acquired immunodeficiency disorders?

Factors such as HIV infection or certain medications.

What are inflammatory disorders?

Conditions resulting from dysregulation of the immune system, associated with chronic inflammation, such as inflammatory bowel disease (IBD) and psoriasis.

How does a compromised immune system affect cancer risk?

It may struggle to recognize and eliminate cancer cells, increasing the risk of cancer development and progression.

What is a potential consequence of autoimmune diseases on organs?

The immune system's attack can lead to inflammation and damage in various organs, causing long-term complications.

What are hypersensitivity reactions?

Exaggerated immune responses to certain stimuli, ranging from mild allergic reactions to severe conditions like anaphylaxis.

What is chronic fatigue syndrome (CFS) and its potential link to immune dysfunction?

A condition characterized by persistent, unexplained fatigue, with some evidence suggesting that immune dysfunction may play a role.

What are secondary infections in the context of immune dysfunction?

Infections that occur due to a weakened immune system, such as opportunistic infections in individuals with HIV/AIDS.

What is ELISA in immunology?

A serological test that detects the presence of antibodies or antigens in a patient's blood, used for diagnosing diseases like HIV and hepatitis.

What is the purpose of the Western Blot test?

It is often used as a confirmatory test for diseases like HIV, separating proteins and identifying specific antibodies in a patient's blood.

What is the purpose of Direct Immunofluorescence Assays (IFA)?

To detect the presence of antigens directly in patient samples using fluorescently labeled antibodies.

How does Indirect Immunofluorescence Assays (IFA) work?

It detects antibodies in patient serum by using a secondary fluorescently labeled antibody.

What does the Widal Test diagnose?

Typhoid fever by detecting antibodies against Salmonella typhi.

What is the Rapid Plasma Reagin (RPR) Test used for?

Diagnosing syphilis.

What is the function of enzyme immunoassays like direct ELISA?

They use an enzyme-antibody conjugate to deliver a detectable substrate to the site of an antigen.

What does a western blot test identify?

Specific bands on a protein gel using antibodies, often used for detecting antibodies against HIV.

What is the Classic Complement Fixation Test used to measure?

The activity of the complement system in response to antigen-antibody complexes, used for diseases like Brucellosis.

What does Polymerase Chain Reaction (PCR) do?

Amplifies and detects nucleic acids (DNA or RNA) of pathogens, providing highly sensitive and specific results.

What is the advantage of Real-time PCR (qPCR)?

It allows for the quantification of DNA or RNA during the amplification process.

What is the purpose of Flow Cytometry Immunophenotyping?

To identify and quantify specific immune cells in the blood, aiding in the diagnosis of immunodeficiency disorders.

How does the complement fixation test indicate the presence of antibodies?

If antibodies are present, complement fixation occurs, preventing hemolysis of added sheep red blood cells.

What can elevated levels of cytokines indicate?

An inflammatory response associated with infection.

What is the Tuberculin Skin Test (Mantoux Test) used for?

Diagnosing tuberculosis by assessing the delayed-type hypersensitivity reaction.

What is Next-Generation Sequencing (NGS) used for in diagnostics?

To sequence the entire genome of pathogens for detailed analysis and identification.

What do Antibody Neutralization Tests determine?

The ability of antibodies to neutralize the infectivity of a pathogen.

What factors influence the choice of diagnostic method for infectious diseases?

The type of pathogen, the stage of infection, and the resources available in the diagnostic laboratory.

What is the procedure for reading the Mantoux skin test?

The test should be read in 48-72 hours, with a positive result indicated by redness, swelling, or hardness.

What is the significance of the raised wheal in the Mantoux skin test?

It indicates an immune response to the tuberculin protein derivative injected.

What does flow cytometry measure in a sample?

The fluorescence intensity of each cell as it passes through a laser-excited capillary.

What type of sample is used in the western blot test for HIV?

Patient serum samples containing antibodies.

What does the enzyme substrate in enzyme immunoassays do?

It converts from a colorless molecule into a colored end product or fluoresces after enzyme activation.

What is the role of antibodies in the western blotting process?

They are used to identify specific proteins on the gel.

What does the presence of antibodies in the complement fixation test indicate?

That complement fixation will occur, leading to no hemolysis of sheep red blood cells.