Immunology: Kinetics, Cytokines, Complement, and Hypersensitivity

What are the four phases of antibody synthesis?

Lag Phase, Log Phase, Plateau, Decline

What occurs during the Lag Phase of antibody synthesis?

No antibody is produced.

What characterizes the Log Phase of antibody synthesis?

It is the exponential phase with increased antibody production.

What happens during the Plateau phase of antibody synthesis?

Antibody production equals antibody degradation.

What occurs during the Decline phase of antibody synthesis?

There is increased antibody degradation.

What is the Primary Immune Response?

It occurs after the first exposure to an immunogen and has a longer duration.

What is the Secondary Immune Response?

It occurs after repeated exposure to the same immunogen and has a higher antibody titer.

What is the major antibody produced during the Primary Immune Response?

IgM

What role do cytokines play in the immune system?

They regulate the immune system and orchestrate both innate and adaptive responses.

What is pleiotropy in the context of cytokines?

A single cytokine can produce many different actions.

What does redundancy mean regarding cytokines?

Different cytokines may share similar actions.

What is synergism in cytokine effects?

Cytokines complement and enhance each other's actions.

What is antagonism in cytokine action?

One cytokine may counteract the action of another.

What is cascade induction in cytokines?

Cytokines activate target cells to produce additional cytokines.

What is the function of IL-1?

It is an endogenous pyrogen that is pro-inflammatory and helps in Ig synthesis.

What is the role of TNF-alpha?

It mediates cytotoxic and inflammatory reactions, especially in the presence of LPS from Gram-negative bacteria.

What does the complement system do?

It enhances host defense mechanisms against foreign cells through a series of proteins.

What are the three pathways of complement activation?

Classical, Alternative, and Lectin pathways.

What is the role of C3 convertase in the complement system?

It is crucial for the activation of the complement cascade.

What are anaphylatoxins?

They increase vascular permeability and trigger the release of histamine from basophils and mast cells.

What is the CH50 Hemolytic assay used for?

It evaluates the complement components of the Classical pathway.

What does the AH50 Hemolytic assay evaluate?

It assesses the complement components of the Alternative pathway.

What is the Complement Fixation Test?

A test that uses complement as a reagent to indicate the presence of specific antigens or antibodies.

What is hypersensitivity in the immune response?

A heightened or exaggerated state of immune responsiveness.

What are the most common complement deficiencies?

C1, C2, C4 deficiencies.

What is the significance of C3 in the complement system?

C3 is required in all pathways and is the most abundant complement protein.

What is the role of complement regulatory proteins?

They inhibit the complement system to prevent damage to host cells.

What is the function of Factor H in the complement system?

It acts as a cofactor for C3b inactivation by factor I.

What is the main source of cytokines?

They are produced by various immune cells, including T cells and macrophages.

What classification system did Philip Gell and Robin Coombs devise?

A classification system based on four categories of hypersensitivity.

What type of hypersensitivity is mediated by IgE?

Type I hypersensitivity, which includes anaphylaxis and hay fever.

What is the time frame for Type IV hypersensitivity reactions?

24-48 hours after exposure.

What is the mechanism of Type II hypersensitivity?

Antibody-mediated cell lysis due to antibody and complement.

What are examples of Type II hypersensitivity reactions?

Food allergies, bronchial asthma, transfusion reactions, and autoimmune conditions like Goodpasture syndrome.

What characterizes Type III hypersensitivity?

Deposition of immune complexes in host tissues, leading to systemic inflammation.

What are examples of Type III hypersensitivity reactions?

Serum sickness, Arthus reaction, systemic lupus erythematosus (SLE), and rheumatoid arthritis (RA).

What is the primary immune mechanism involved in Type IV hypersensitivity?

Cell-mediated immunity involving sensitized T cells.

What are common causes of contact dermatitis?

Nickel, rubber, poison ivy, and cosmetics.

What is the purpose of the Tuberculin test (PPD)?

To detect past or present infection of tuberculosis through a skin reaction.

What is the standard procedure for serum preparation in serology?

Blood is allowed to clot, then centrifuged; serum is stored at 2-8°C for <72 hours and at -20°C for >72 hours.

What is the definition of antibody titer?

The reciprocal of the highest dilution of serum where the antibody is still detectable.

What does a fourfold increase in antibody titer indicate?

Current infection.

What is clinical sensitivity in diagnostic testing?

The percentage of persons with the disease who have a positive test result.

What is clinical specificity in diagnostic testing?

The percentage of persons without the disease who have a negative test result.

What does positive predictive value indicate?

The probability of having the disease if the test result is abnormal.

What does negative predictive value indicate?

The probability of not having the disease if the test result is normal.

What is the difference between precipitation and agglutination reactions?

Precipitation involves soluble antigens forming insoluble complexes, while agglutination involves visible aggregates of particles.

What is avidity in the context of antigen-antibody binding?

The overall strength of binding, representing the sum of all affinities involved.

What is the zone of equivalence in immunological reactions?

The point where the number of multivalent sites of antigen and antibody are approximately equal, leading to optimum precipitation/agglutination.

What is the prozone phenomenon?

A false negative reaction due to an excess of antibodies in a test.

What is the purpose of turbidimetry in immunology?

To measure the decrease in light intensity caused by antibody-antigen complexes in solution.

What does nephelometry measure in immunological tests?

The amount of light scattered in a solution containing antibody-antigen complexes.

What is the principle behind the Oudin method in immunodiffusion?

Antigen and antibody diffuse independently in agar gel, resulting in a distinct pattern of precipitation.

What does a smooth curve in precipitation patterns indicate?

Epidemiological identity between antigens.

What does a crossed-line pattern in precipitation indicate?

Non-identity between antigens.

What does spur formation in precipitation patterns indicate?

Partial identity between antigens.