Immunology Overview and History

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Questions and Answers

What is the primary role of the complement system in the immune response?

To activate B cells for antibody production

To enhance the ability of antibodies and phagocytic cells (correct)

To produce antibodies exclusively

To directly kill all pathogens encountered

How are complement proteins activated?

By proteolytic cleavage of their zymogen precursors (correct)

Via cytokine signaling from T cells

Through a cycle of phosphorylation events

Through direct binding to pathogens

What does cross reactivity in antibodies refer to?

An antibody's inability to recognize small molecular changes

An antibody's capacity to react with different types of pathogens

An antibody's ability to bind only to its specific antigen

An antibody's ability to react with multiple antigenic determinants (correct)

What initiates the cascade of activation in the complement system?

Cleavage of an inactive zymogen to an active enzyme Signup and view all the answers

What type of enzyme is generated during the complement activation cascade?

Serine protease Signup and view all the answers

What was the significance of Edward Jenner's experiment with cowpox and smallpox?

It was the first recorded vaccination. Signup and view all the answers

Which of the following describes the primary function of the immune system?

To protect the body against disease. Signup and view all the answers

In what way does the innate immune system respond to pathogens?

It recognizes general features common to many invaders. Signup and view all the answers

What is a key characteristic of the innate immune system?

It provides an immediate response upon detection of threats. Signup and view all the answers

What happens when the immune system fails to function properly?

It can lead to various immune-mediated disorders. Signup and view all the answers

How does the immune system distinguish between self and non-self cells?

By recognizing general characteristics of invaders. Signup and view all the answers

Which type of immunity is characterized by its non-specific response?

Innate immunity. Signup and view all the answers

What does the term 'antigen-independent response' refer to in the context of the innate immune system?

Responding to pathogens without prior exposure. Signup and view all the answers

What is the main purpose of using a capture antibody in an assay?

To bind the target antigen to a solid surface Signup and view all the answers

What is one advantage of using an enzyme-linked conjugated antibody in assays?

It produces a measurable signal through color change Signup and view all the answers

In a competitive assay, what is indicated by a lower assay signal?

Higher levels of sample antigen Signup and view all the answers

Which statement accurately describes the secondary antibody's function?

It enhances the signal for detection Signup and view all the answers

What challenge may arise when choosing the right antibody for an assay?

It can be time-consuming to determine the best fit Signup and view all the answers

What is a limitation of using a competitive assay format?

It offers low specificity Signup and view all the answers

Which aspect is NOT generally associated with Western Blotting?

It can quantify all types of antigens Signup and view all the answers

What does the term 'sandwich' refer to in the context of antibody assays?

A capture antibody binding a sample antigen with detection antibody Signup and view all the answers

What is the role of Factor D in the complement pathway?

It cleaves factor B into Ba and Bb. Signup and view all the answers

Which complex is responsible for cleaving C5 in the complement pathway?

C3bBbP Signup and view all the answers

What is one of the key functions of the complement system?

It enhances inflammation and facilitates phagocytosis. Signup and view all the answers

Which of the following statements about primary lymphoid organs is true?

They are responsible for the maturation of T and B cells. Signup and view all the answers

What happens to necrotic cells in relation to the complement system?

They activate complement and are cleared by phagocytes. Signup and view all the answers

How does the complement system respond to viral infections?

It opsonizes and lyses viruses for phagocytosis. Signup and view all the answers

What completes the loop created by C3 convertase in the complement pathway?

Additional cleavage of C3 by C3bBb. Signup and view all the answers

What is the final outcome of all complement pathways?

Formation of the Membrane Attack Complex (MAC). Signup and view all the answers

What is the purpose of heating the sample during sample preparation in Western blotting?

To denature proteins and reduce disulfide bonds Signup and view all the answers

Which component is essential in the blocking step to prevent non-specific binding of antibodies in Western blotting?

BSA or milk Signup and view all the answers

What is the role of gel electrophoresis in the Western blotting process?

To separate proteins based on their size Signup and view all the answers

During the membrane transfer phase, in which direction do negatively charged proteins migrate?

From the gel to the positive side of the membrane Signup and view all the answers

What is the most likely consequence of inadequate wash steps during Western blotting?

Reduced signal-to-noise ratio Signup and view all the answers

What type of substrate may be used in the detection step of Western blotting?

Chemiluminescent substrate kit Signup and view all the answers

What is the purpose of using a total protein stain during immunodetection in Western blotting?

To assess the transfer efficiency of proteins Signup and view all the answers

Which protein characteristic dictates how proteins migrate during gel electrophoresis?

Molecular weight Signup and view all the answers

Study Notes

A Brief History of Immunology

Edward Jenner's 1798 observation of milkmaids' immunity to smallpox after cowpox infection led to the development of the smallpox vaccine.

What is Immunology?

The study of the immune system and its role in protecting the body against disease.
Focuses on molecules, cells, organs, and systems responsible for recognizing and eliminating foreign materials.

Overview of Immune System Function

Defends against microbes, fungi, viruses, pathogens, and transplanted organs.
Destroys abnormal or dead cells.
Distinguishes between "self" and "non-self" cells.

Immune System Dysfunction

Deficiencies or dysfunctions can cause disorders including cancers and autoimmune diseases (type 1 diabetes, rheumatoid arthritis, lupus).

Major Subdivisions of the Immune System

Innate Immune System: First line of defense; non-specific, immediate maximal response, no immunological memory.
Adaptive Immune System: Specific, slower response, immunological memory (discussed in later lectures).

Cross Reactivity

An antibody's ability to react with more than one antigenic determinant.

The Complement System

Part of the innate immune system; enhances antibody and phagocytic cell function.
Clears microbes and damaged cells, promotes inflammation, attacks pathogen cell membranes.
Composed of inactive precursor proteins (zymogens) synthesized by the liver; activated by proteolytic cleavage.
Activation occurs through a triggered-enzyme cascade.
All pathways (Classical, Lectin, Alternative) converge at C3 cleavage.
Main functions: inflammation, phagocytosis, Membrane Attack Complex (MAC) formation.
Other key functions: removal of immune complexes and necrotic cells; responses to viruses.

Primary and Secondary Lymphoid Organs

Primary Lymphoid Organs: Bone marrow (hematopoietic stem cell production, B cell and NK cell maturation); Thymus (T cell maturation).
Secondary Lymphoid Organs: Sites of immune responses (discussed in later lectures).

Enzyme-Linked Immunosorbent Assay (ELISA)

Sandwich ELISA: Uses capture and detection antibodies to create a "sandwich" for target detection. Highly sensitive and specific, rapid, requires little sample preparation.
Competitive ELISA: Sample antigen competes with labeled antigen for antibody binding. Lower signal indicates more antigen in sample. Less specific, useful for small targets.

Western Blotting

Detects specific proteins in a mixture; determines protein size and amount.
Procedure: Sample preparation (lysis, reduction, denaturation), gel electrophoresis (protein separation by size), membrane transfer (proteins transferred to membrane), immunodetection (blocking, primary/secondary antibody incubation, detection).
Membrane Transfer: Proteins transferred from gel to membrane using an electrical current in a cold buffer.
Blocking Step: Prevents non-specific antibody binding (using BSA or milk).
Wash Steps: Remove unbound reagents to reduce background.

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Description

Explore the fascinating history and functions of the immune system. This quiz covers key concepts from Edward Jenner's smallpox vaccine development to the intricacies of immune system dysfunctions and subdivisions. Test your knowledge on how our bodies defend against diseases and what happens when this system falters.