Introduction to Immunology

55 Questions

What is the role of soluble factors produced by a specific immune response in relation to phagocytic cells?

They augment the activity of phagocytic cells.

What is the purpose of soluble mediators produced during an inflammatory response?

To attract cells of the immune system.

How do the adaptive and innate immune systems work together?

Through a carefully regulated interplay to eliminate a foreign invader.

What are the two major groups of cells involved in an effective immune response?

T lymphocytes and antigen-presenting cells.

Where are lymphocytes produced?

In the bone marrow through the process of hematopoiesis.

What is the unique feature of lymphocytes that enables them to mediate immune responses?

They produce and display antigen-binding cell-surface receptors.

What are the defining immunologic attributes of lymphocytes?

Specificity, diversity, memory, and self/nonself recognition.

What are the two major populations of lymphocytes?

B lymphocytes (B cells) and T lymphocytes (T cells).

Where do lymphocytes circulate and reside?

In the blood and lymphatic systems, and in various lymphoid organs.

What is the significance of the interplay between adaptive and innate immunity?

It serves to eliminate a foreign invader.

What is the function of the variable region of an antibody molecule?

The variable region is responsible for recognizing and binding to a specific antigen.

What is the purpose of the enzyme reaction in ELISA?

The purpose of the enzyme reaction in ELISA is to detect and quantify the target molecule.

What is the significance of antibody specificity?

Antibody specificity refers to the ability of an antibody to recognize and bind to a specific antigen, allowing for precise immune responses.

What is the difference between the heavy chains and light chains of an antibody molecule?

The heavy chains (H chains) and light chains (L chains) of an antibody molecule differ in their structure and function, with the H chains forming the constant region and the L chains forming the variable region.

What is the name given to the protein molecules that are produced and secreted by B cells?

The protein molecules produced and secreted by B cells are called immunoglobulins (Ig) or antibodies.

What are the two regions of an antibody formed when it is cleaved by the protease papain?

Fab region and Fc region

What is the term for the ability of an antibody to precisely recognize a specific antigen?

Antibody specificity

What is the primary function of IgG in the human body?

IgG detoxifies harmful substances and is important in the recognition of antigen-antibody complexes by leukocytes and macrophages.

How do B cells recognize a vast number of antigens despite a limited number of genes?

Gene rearrangement

What is the term for the body's ability to defend itself against repeated infections of the same pathogen?

Immunological memory

What is the significance of IgA in breast milk?

IgA in breast milk protects the gastrointestinal tract of neonates from pathogens.

What is the process called when mature B cells differentiate into cells that produce increasing amounts of secreted immunoglobulins and start to produce immunoglobulin isotypes other than IgM and IgD?

Immunoglobulin class switching.

Why do tens to hundreds of millions of B cells not recognize and attack self-tissues?

Immune tolerance

What is the definition of polyclonal antibodies?

Polyclonal antibodies are generated by immunizing animals with an antigen, which induces the production of high levels of antibodies into the blood.

What is the original role of IgE?

To protect against parasites.

What is the advantage of using hybridomas in producing monoclonal antibodies?

Hybridomas allow for the indefinite production of a single antibody with high affinity and specificity, as they are a fusion of antibody-producing B cells with immortalized cancer cells.

How do monoclonal antibodies against the same antigen differ from each other?

Each clone reacts to different epitopes on the same antigen and has different suitable applications.

What is the phage display method used for?

The phage display method is used to select antibodies against a target molecule from a large population of antibody phages.

What is the main difference between polyclonal and monoclonal antibodies in terms of epitope recognition?

Polyclonal antibodies react to multiple epitopes, whereas monoclonal antibodies react to a single epitope.

Why do monoclonal antibodies tend to be sensitive to modifications such as labeling and removal of the Fc region?

Monoclonal antibodies are homogeneous, so any modifications can affect the binding ability of the entire antibody population.

What is the advantage of using polyclonal antibodies as secondary antibodies in detection assays?

They provide a higher sensitivity of detection due to the ability of multiple antibodies to bind to a primary antibody molecule.

Why are polyclonal antibodies more resistant to protease digestion than monoclonal antibodies?

Because multiple different antibody molecules are present, making it less likely for proteases to affect antigen-binding ability.

What is the purpose of the third step in antibody purification, gel filtration chromatography?

To remove contaminants remaining after step 2 and exchange the buffer.

What is the difference between Protein A and Protein G in antibody purification?

Protein A is a cell wall protein of Staphylococcus aureus, while Protein G is a cell wall protein isolated from group G Streptococci, and they differ in their ability to bind to Ig subclasses and species.

What is the advantage of antigen-affinity purification over Protein A/G affinity chromatography?

It provides a higher yield of antigen-specific antibodies.

What is the advantage of using polyclonal antibodies as secondary antibodies in detection assays?

They provide a higher sensitivity of detection and are commonly used.

Why do monoclonal antibodies tend to be sensitive to modifications such as labeling and removal of the Fc region?

They are highly sensitive to protease digestion, which can result in digestion outside the intended regions or loss of antigen-binding ability.

What is the purpose of the first step in antibody purification?

To partially remove solid materials and proteins other than the antibodies.

What is the difference between Protein A and Protein G in antibody purification?

They differ in their ability to bind to Ig subclasses and between species.

Why are polyclonal antibodies more resistant to protease digestion than monoclonal antibodies?

Because multiple different antibody molecules are present, antigen-binding ability tends to be unaffected.

What is the purpose of the third step in antibody purification, gel filtration chromatography?

To remove contaminants remaining after step 2 and exchange the buffer.

How do polyclonal antibodies differ from monoclonal antibodies in terms of epitope recognition?

Polyclonal antibodies can recognize multiple epitopes, while monoclonal antibodies recognize a single epitope.

What is the advantage of antigen-affinity purification over Protein A/G affinity chromatography?

It provides a higher yield of antigen-specific antibodies.

What is the purpose of affinity chromatography in antibody purification?

To isolate antibodies that bind to a specific antigen or protein.

Why are antibodies often modified by proteases?

To add a label or remove the Fc region to reduce non-specific reaction.

Why are polyclonal antibodies more commonly used as secondary antibodies in detection assays?

Because they provide a higher sensitivity of detection (amplification of the signal) due to multiple antibody molecules binding to a primary antibody molecule.

What is the advantage of using polyclonal antibodies in terms of modification, such as labeling and removal of the Fc region?

They are less sensitive to modifications because multiple different antibody molecules are present, making them more amenable to modification.

What is the purpose of centrifugation or filtration in the first step of antibody purification?

To partially remove solid materials and proteins other than the antibodies.

What is the difference between Protein A and Protein G in antibody purification?

The ability of Protein G and Protein A to bind to Ig differs between Ig subclasses and between species.

What is the advantage of antigen-affinity purification over Protein A/G affinity chromatography?

It provides a higher yield of antigen-specific antibodies, although the total amount of recovered antibodies is lower.

Why are monoclonal antibodies sensitive to protease digestion?

Because they can be digested outside the intended regions, or lose antigen-binding ability, due to their high sensitivity to protease digestion.

What is the purpose of gel filtration chromatography in the third step of antibody purification?

To remove contaminants remaining after step 2 and exchange the buffer.

What is the significance of the Fc region in antibody purification using Protein A or Protein G?

The Fc region is specifically bound by Protein A or Protein G, allowing for the purification of IgG.

Why are antibodies often modified by proteases?

To add a label or to remove the Fc region to reduce non-specific reaction.

What is the purpose of affinity chromatography in antibody purification?

To isolate antibodies by binding to a specific protein or antigen.

Study Notes

Immunology

The immune system is a defense system that protects animals from invading pathogenic microorganisms and cancer.
It generates a variety of cells and molecules that can specifically recognize and eliminate foreign invaders.
The immune system has two main functions: recognition and response.

Recognition

The immune system can recognize subtle chemical differences between different foreign pathogens.
It can discriminate between foreign molecules and the body's own cells and proteins.
Recognition of a foreign pathogen leads to an immune response.

Response

The immune system recruits various cells and molecules to mount an appropriate response to eliminate the pathogen.
This response is called an effector response.
The response is specific to each type of pathogen.

Innate Immunity

Innate immunity is the first line of defense against infection.
It provides immediate, non-specific defense against infection.
Components of innate immunity include:
- Anatomic barriers (e.g. skin, mucous membranes)
- Physiologic barriers (e.g. temperature, pH)
- Phagocytic cells (e.g. macrophages, neutrophils)
- Inflammatory responses

Anatomic Barriers

The skin and mucous membranes provide a physical barrier against infection.
The skin has two layers: the epidermis and dermis.
The epidermis contains layers of tightly packed epithelial cells.
The dermis contains blood vessels, hair follicles, sebaceous glands, and sweat glands.

Physiologic Barriers

Temperature and pH can inhibit the growth of certain microorganisms.
Gastric acidity is an example of a physiologic barrier to infection.
Various soluble factors, such as lysozyme, interferon, and complement, can also contribute to innate immunity.

Phagocytic Cells

Phagocytic cells, such as macrophages and neutrophils, can ingest and destroy pathogens.
Phagocytosis is one type of endocytosis, where a cell's plasma membrane expands around the particulate material to form a phagosome.

Inflammatory Response

The inflammatory response is a complex sequence of events that stimulates immune responses.
It is triggered by tissue damage or the presence of a pathogen.
The classic signs of inflammation are:
- Redness (rubor)
- Swelling (tumor)
- Heat (calor)
- Pain (dolor)
- Loss of function (functio laesa)

Adaptive Immunity

Adaptive immunity is capable of recognizing and selectively eliminating specific foreign microorganisms and molecules.
It is specific to each individual and is a reaction to specific antigenic challenges.
Adaptive immunity involves the activation of lymphocytes and the production of antibodies.### Adaptive Immunity Characteristics
Adaptive immunity displays four characteristic attributes: antigenic specificity, diversity, immunologic memory, and self/nonself recognition
Antigenic specificity allows the immune system to distinguish subtle differences among antigens, even between two protein molecules that differ in only a single amino acid
Diversity enables the immune system to recognize billions of unique structures on foreign antigens
Immunologic memory enables the immune system to respond more strongly to a second encounter with the same antigen, providing life-long immunity to many infectious agents
Self/nonself recognition allows the immune system to distinguish between self and nonself molecules, responding only to nonself molecules

Interplay between Adaptive and Innate Immunity

Adaptive immunity is not independent of innate immunity, with phagocytic cells crucial to nonspecific immune responses involved in activating the specific immune response
Soluble factors produced by a specific immune response augment the activity of phagocytic cells
The immune response regulates the intensity of the inflammatory response through the interplay of adaptive and innate immunity

The Adaptive Immune System

An effective immune response requires cooperation between lymphocytes and antigen-presenting cells
Lymphocytes are produced in the bone marrow through hematopoiesis and mediate the defining immunologic attributes of specificity, diversity, memory, and self/nonself recognition
There are two major populations of lymphocytes: B lymphocytes (B cells) and T lymphocytes (T cells)

Enzyme-Linked Immunosorbent Assay (ELISA)

ELISA is a method of target antigen or antibody capture in samples using a specific antibody or antigen and detection/quantitation using an enzyme reaction with its substrate.
Various antigen-antibody combinations are used, including an enzyme-labeled antigen or antibody.
Enzyme activity is measured colorimetrically using a substrate that changes color when modified by the enzyme.

Antibodies

Antibodies are proteins produced and secreted by B cells that bind to foreign substances, such as pathogens.
The term "antibody" refers to its function of binding to an antigen.
Another name for this protein molecule is immunoglobulin (abbreviated Ig).
Antibodies are Y-shaped molecules consisting of two heavy chains (H chains) and two light chains (L chains).
Each antibody recognizes a specific antigen, known as "antibody specificity."

Variable and Constant Regions

The N-terminal domains of the H and L chains are called the variable regions (V regions).
The rest of the molecule is called the constant region (C region).
The amino acid sequence of the V region varies from antibody to antibody, accounting for the high degree of three-dimensional structural diversity of immunoglobulin chains.

Fab and Fc Regions

The protease papain cleaves antibodies above the disulfide bonds that connect the two H chains, generating three fragments.
The two N-terminal fragments are called the Fab region, and the C-terminal fragment is called the Fc region.
The Fab region includes the antigen-binding site.

Antibody Diversity and Specificity

Antibodies against a variety of antigens preexist in the body, known as "antibody diversity."
Each B cell produces one kind of antibody, but tens to hundreds of millions of different B cells are circulating in the body.
Antibodies precisely recognize toxins and pathogens, known as "antibody specificity."

Gene Rearrangement

Antibody-producing B cells are produced in the bone marrow and mature in the periphery.
During B-cell maturation, the antibody genes (immunoglobulin genes) undergo recombination, generating an enormous repertoire of antigen-binding sites (the variable region).

Immunoglobulin Class Switching

B cells expressing plasma membrane-bound IgM and IgD (mature B cells) are activated upon encounter with a specific antigen and begin to proliferate and produce secretory IgM and IgD.
With further activation, these mature B cells differentiate into cells that produce increasing amounts of secreted immunoglobulins and start to produce immunoglobulin isotypes other than IgM and IgD.

Polyclonal and Monoclonal Antibodies

Polyclonal antibodies are generated by injecting an antigen into an animal, which induces the production of multiple antibodies that react to the antigen.
Monoclonal antibodies are produced by artificially fusing a single B cell producing an antibody with immortalized cancer cells.
Monoclonal antibodies react to a single epitope on an antigen, while polyclonal antibodies react to multiple epitopes.

Antibody Purification

Antibodies are usually purified by centrifugation or filtration, followed by affinity chromatography (purification with Protein A/G or antigen-affinity purification).
Protein A is a cell wall protein of Staphylococcus aureus that specifically binds to the Fc region of mammalian IgG.
Antigen-affinity purification involves using a column packed with immobilized antigen to isolate antibodies that bind to the antigen.

Enzyme-Linked Immunosorbent Assay (ELISA)

ELISA is a method of target antigen or antibody capture in samples using a specific antibody or antigen and detection/quantitation using an enzyme reaction with its substrate.
Various antigen-antibody combinations are used, including an enzyme-labeled antigen or antibody.
Enzyme activity is measured colorimetrically using a substrate that changes color when modified by the enzyme.

Antibodies

Antibodies are proteins produced and secreted by B cells that bind to foreign substances, such as pathogens.
The term "antibody" refers to its function of binding to an antigen.
Another name for this protein molecule is immunoglobulin (abbreviated Ig).
Antibodies are Y-shaped molecules consisting of two heavy chains (H chains) and two light chains (L chains).
Each antibody recognizes a specific antigen, known as "antibody specificity."

Variable and Constant Regions

The N-terminal domains of the H and L chains are called the variable regions (V regions).
The rest of the molecule is called the constant region (C region).
The amino acid sequence of the V region varies from antibody to antibody, accounting for the high degree of three-dimensional structural diversity of immunoglobulin chains.

Fab and Fc Regions

The protease papain cleaves antibodies above the disulfide bonds that connect the two H chains, generating three fragments.
The two N-terminal fragments are called the Fab region, and the C-terminal fragment is called the Fc region.
The Fab region includes the antigen-binding site.

Antibody Diversity and Specificity

Antibodies against a variety of antigens preexist in the body, known as "antibody diversity."
Each B cell produces one kind of antibody, but tens to hundreds of millions of different B cells are circulating in the body.
Antibodies precisely recognize toxins and pathogens, known as "antibody specificity."

Gene Rearrangement

Antibody-producing B cells are produced in the bone marrow and mature in the periphery.
During B-cell maturation, the antibody genes (immunoglobulin genes) undergo recombination, generating an enormous repertoire of antigen-binding sites (the variable region).

Immunoglobulin Class Switching

B cells expressing plasma membrane-bound IgM and IgD (mature B cells) are activated upon encounter with a specific antigen and begin to proliferate and produce secretory IgM and IgD.
With further activation, these mature B cells differentiate into cells that produce increasing amounts of secreted immunoglobulins and start to produce immunoglobulin isotypes other than IgM and IgD.

Polyclonal and Monoclonal Antibodies

Polyclonal antibodies are generated by injecting an antigen into an animal, which induces the production of multiple antibodies that react to the antigen.
Monoclonal antibodies are produced by artificially fusing a single B cell producing an antibody with immortalized cancer cells.
Monoclonal antibodies react to a single epitope on an antigen, while polyclonal antibodies react to multiple epitopes.

Antibody Purification

Antibodies are usually purified by centrifugation or filtration, followed by affinity chromatography (purification with Protein A/G or antigen-affinity purification).
Protein A is a cell wall protein of Staphylococcus aureus that specifically binds to the Fc region of mammalian IgG.
Antigen-affinity purification involves using a column packed with immobilized antigen to isolate antibodies that bind to the antigen.

Enzyme-Linked Immunosorbent Assay (ELISA)

ELISA is a method of target antigen or antibody capture in samples using a specific antibody or antigen and detection/quantitation using an enzyme reaction with its substrate.
Various antigen-antibody combinations are used, including an enzyme-labeled antigen or antibody.
Enzyme activity is measured colorimetrically using a substrate that changes color when modified by the enzyme.

Antibodies

Antibodies are proteins produced and secreted by B cells that bind to foreign substances, such as pathogens.
The term "antibody" refers to its function of binding to an antigen.
Another name for this protein molecule is immunoglobulin (abbreviated Ig).
Antibodies are Y-shaped molecules consisting of two heavy chains (H chains) and two light chains (L chains).
Each antibody recognizes a specific antigen, known as "antibody specificity."

Variable and Constant Regions

The N-terminal domains of the H and L chains are called the variable regions (V regions).
The rest of the molecule is called the constant region (C region).
The amino acid sequence of the V region varies from antibody to antibody, accounting for the high degree of three-dimensional structural diversity of immunoglobulin chains.

Fab and Fc Regions

The protease papain cleaves antibodies above the disulfide bonds that connect the two H chains, generating three fragments.
The two N-terminal fragments are called the Fab region, and the C-terminal fragment is called the Fc region.
The Fab region includes the antigen-binding site.

Antibody Diversity and Specificity

Antibodies against a variety of antigens preexist in the body, known as "antibody diversity."
Each B cell produces one kind of antibody, but tens to hundreds of millions of different B cells are circulating in the body.
Antibodies precisely recognize toxins and pathogens, known as "antibody specificity."

Gene Rearrangement

Antibody-producing B cells are produced in the bone marrow and mature in the periphery.
During B-cell maturation, the antibody genes (immunoglobulin genes) undergo recombination, generating an enormous repertoire of antigen-binding sites (the variable region).

Immunoglobulin Class Switching

B cells expressing plasma membrane-bound IgM and IgD (mature B cells) are activated upon encounter with a specific antigen and begin to proliferate and produce secretory IgM and IgD.
With further activation, these mature B cells differentiate into cells that produce increasing amounts of secreted immunoglobulins and start to produce immunoglobulin isotypes other than IgM and IgD.

Polyclonal and Monoclonal Antibodies

Polyclonal antibodies are generated by injecting an antigen into an animal, which induces the production of multiple antibodies that react to the antigen.
Monoclonal antibodies are produced by artificially fusing a single B cell producing an antibody with immortalized cancer cells.
Monoclonal antibodies react to a single epitope on an antigen, while polyclonal antibodies react to multiple epitopes.

Antibody Purification

Antibodies are usually purified by centrifugation or filtration, followed by affinity chromatography (purification with Protein A/G or antigen-affinity purification).
Protein A is a cell wall protein of Staphylococcus aureus that specifically binds to the Fc region of mammalian IgG.
Antigen-affinity purification involves using a column packed with immobilized antigen to isolate antibodies that bind to the antigen.

This quiz covers the basics of the immune system, its functions, and its mechanisms to protect animals from pathogens and cancer.

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