Immunity MCQ Quiz - Objective Question with Answer for Immunity - Download Free PDF

The correct answer is C, D, E only

Concept:

• Lymphoid organs are the organs where the origin and/or maturation and proliferation of lymphocytes occur.
• The primary lymphoid organs are bone marrow and thymus, where immature lymphocytes differentiate into antigen-sensitive lymphocytes.
• After maturation, the lymphocytes migrate to secondary lymphoid organs like the spleen, lymph nodes, tonsils, Peyer’s patches of small intestine, and appendix.
• The secondary lymphoid organs provide the sites for interaction of lymphocytes with the antigen, which then proliferate to become effector cells.

Explanation:

• Spleen (C): The spleen filters blood and is a site where lymphocytes interact with blood-borne antigens. It plays a crucial role in immune responses to pathogens circulating in the bloodstream.
• Lymph Nodes (D): Lymph nodes are distributed throughout the body and filter lymph. They trap antigens from lymphatic fluid and allow interaction between lymphocytes and antigens, activating adaptive immune responses.
• Peyer’s Patches (E): Peyer’s patches are specialized mucosa-associated lymphoid tissues in the small intestine. They monitor intestinal contents for antigens and are essential for immune responses in the gut-associated lymphoid tissue (GALT).

Incorrect Options:

• Thymus (A): The thymus is a primary lymphoid organ responsible for the maturation of T cells. 
• Bone Marrow (B): The bone marrow is another primary lymphoid organ responsible for the development and maturation of B cells.

The correct answer is IgA

Explanation:

• Colostrum is the first form of milk produced immediately following the delivery of the newborn.
• It is rich in antibodies, especially IgA, which play a crucial role in providing immunity to the newborn during the first few days of life.
• IgA antibodies are essential for mucosal immunity and are found in high concentrations in colostrum.
• It plays a significant role in protecting the mucous membranes lining the respiratory and gastrointestinal tracts. By providing passive immunity, IgA helps to safeguard the newborn from infections during the early stages of life.

Other Options:

• IgG: While Immunoglobulin G (IgG) is the most common antibody in blood and extracellular fluid, providing long-term protection. IgG is mainly transferred to the newborn through the placenta during pregnancy.
• IgM: Immunoglobulin M (IgM) is the first antibody to respond to an infection and is primarily found in the blood and lymphatic fluid.
• IgE: Immunoglobulin E (IgE) is associated with allergic reactions and is found in very small amounts in the body. 

The correct option is:1  

Explanation:

• IgA → C) Mucosal immunity: IgA is primarily found in mucosal secretions such as saliva, tears, and mucus, playing a key role in protecting mucosal surfaces from pathogens.
• IgE → A) Allergy response: IgE is involved in allergic reactions and defense against parasitic infections by binding to allergens and triggering the release of histamines from mast cells and basophils.
• IgG → B) Passive immunity via placenta: IgG is the most abundant immunoglobulin in circulation and is the only one capable of crossing the placenta, providing passive immunity to the fetus.
• IgM → D) First response in primary infections: IgM is the first immunoglobulin produced during the initial immune response and is effective in forming antigen-antibody complexes due to its pentameric structure.

Key Points

• IgA: Found in high concentrations in breast milk, providing immunity to infants. 
• IgE: Excessive IgE levels are associated with conditions like asthma and anaphylaxis.
• IgG: Plays a significant role in long-term immunity due to its persistence after infections or vaccinations.
• IgM: Acts as an effective opsonin and initiates the classical complement pathway for pathogen destruction.

The correct answer is Thymus

Explanation:

• The lymphoid organs are tissues or structures where lymphocytes are formed, mature, and proliferate. They are categorized into primary and secondary lymphoid organs.
• Primary lymphoid organs are where lymphocytes mature. Secondary lymphoid organs are where lymphocytes become activated and immune responses are initiated.
  • Thymus: A primary lymphoid organ. It is where T lymphocytes (T cells) mature. After maturation, they migrate to secondary lymphoid organs to participate in immune responses.
  • Spleen: A secondary lymphoid organ. It filters blood, removes old red blood cells, and is a site for immune responses against blood-borne pathogens.
  • Lymph nodes: Secondary lymphoid organs scattered throughout the body. They filter lymphatic fluid and provide a site for immune cells to interact with antigens and mount an immune response.
  • MALT (Mucosa-associated lymphoid tissue): This is also a secondary lymphoid tissue. It includes immune tissues like the tonsils, Peyer's patches, and other mucosal tissues that respond to pathogens encountered at mucosal surfaces.

The correct answer is: (1) Only 1 and 3 are correct.

Explanation:

1. Antigen presentation is a process where immune cells, such as dendritic cells, present fragments of pathogens to T-cells to initiate an immune response.

   • This statement is true. Antigen presentation involves immune cells like dendritic cells, macrophages, and B-cells presenting fragments of pathogens (antigens) on their surface to T-cells, initiating an adaptive immune response.

2. Antibody production is carried out by T-cells that are activated upon encountering a specific antigen, leading to the production of antibodies that help in neutralizing pathogens.

   • This statement is false. Antibody production is primarily carried out by B-cells, not T-cells. When B-cells are activated by helper T-cells, they differentiate into plasma cells that produce antibodies to neutralize pathogens.

3. Phagocytosis is the process by which certain cells, like macrophages, engulf and digest pathogens or debris from the body.

   • This statement is true. Phagocytosis is the process where immune cells like macrophages, neutrophils, and dendritic cells engulf pathogens or debris and digest them, playing a critical role in the innate immune response.

4. Thymic education refers to the process where B-cells mature in the thymus and undergo selection to ensure self-tolerance and the ability to recognize foreign antigens.

   • This statement is false. Thymic education (or thymic selection) occurs in the thymus, but it refers to the maturation and selection of T-cells, not B-cells. T-cells undergo positive and negative selection in the thymus to ensure self-tolerance and the ability to recognize foreign antigens.

The correct answer is Passive immunization.

• If a person is infected with some deadly microbes to which quick immune response is required, we need to directly inject the preformed antibodies. This type of immunization is known as Passive immunization.
• Passive immunity: When ready-made antibodies are directly given to protect the body against foreign agents, it is called passive immunity.
• Active immunity: When a host is exposed to antigens, which may be in the form of living or dead microbes or other proteins, antibodies are produced in the host body. This type of immunity is called active immunity.

Active vs passive immunity

Concept:

• Cytokines are low molecular proteinaceous chemical messengers that are secreted by the cells of the immunity system in response to stimuli.
• These are secreted by WBCs and various other cells of the body.
• They serve as messengers of the immune system.
• Cytokines bind to specific receptors on the target cells.
• Once bound they induce signal transduction that results in triggering gene expression in the target cell.
• Depending on the type of cell that secretes cytokines, they are of following types:
  1. Lymphokines: Secreted by lymphocytes. These are secreted specifically by T cells. (Functions similar to those mentioned above for cytokines).
  2. Monokines: Secreted by monocytes and macrophages.
  3. Interleukins: Secreted by some leukocytes and act on other leukocytes.
• Apart from this, chemokines are also a special type of cytokine that plays an important role in inflammation.

Important Points

• There are several kinds of lymphokines. 
• Some of these are interferons, granulocyte-macrophage colony-stimulating factors, migration inhibitory factors and lymphotoxin.
• Out of the options given in the question, the most common lymphokine is interferon.

Interferon - 

• Interferons (IFN) are produced in response to an infection caused by a virus.
• These are proteins that are known to interfere with viral replication.
• There are mainly three types of interferons - IFN-α, IFN-ß and IFN-γ.
• Interferons trigger the synthesis of host cell proteins that in turn inhibit viral regulation.
• It increases the expression of the Major Histocompatibility Complex (MHC).
• It also causes the activation of natural killer cells.

 ​

Hence, the correct answer is option 4 (Interferon).

Concept:

• The immunity system provides the body the ability to fight against the different pathogenic organisms or the toxins that damage the tissues and organs.
• The immunity system consists of several structurally and functionally different organs and tissues.
• The organs of the immune system are divided into two groups - Primary lymphoid organs (E.g.: Bone marrow) and Secondary lymphoid organs (E.g.: Tonsils).
• Lymphocytes are the white blood cells that play an important role in the immune system.

Important Points

CLONAL SELECTION:

• Lymphocytes are of two types - B cells and T cells.
• B cells produce antibodies.  Antibodies are the chemicals produced by the immune system in response to the antigenic stimulus. They fight against the antigens or the toxins and neutralize them.
• T cells on the other hand fight against invading pathogens.
• The B cells during differentiation in the bone marrow, is genetically programmed to produce antibodies.
• The antibodies have a unique antigen-binding site.
• These sites known as paratopes are present in the variable region of the heavy and light chains of the immunoglobulin.
• These regions are characterized by an amino acid sequence that varies from one immunoglobulin to other.
• The antigen-binding site is made through a series of gene translocations. These function as B cell receptors.
• During a pathogen attack, antigens come across the cells of the immune system.
• The epitope (site at which antibody binds) present on the antigen will react with only those B-cells that have receptors that fit more or less.
• This in turn activates the B-cells.
• This process is known as clonal selection.
• The B cells thus activated start proliferating rapidly under the influence of cytokines produced by the effector T cells.
• As a result, a large number of clones of the activated B cells are produced.
• All these are the clones of the activated B-cells that have the correct specificity to the antigen.
• This is known as clonal expansion.​
• Based on the above-given information, the only option that correctly explains the clonal selection, as well as the clonal expansion process is the proliferation and differentiation of lymphocytes that occur in response to a specific antigen.

So the correct answer is option 2.

Concept:

• The ability of the human body to fight against the different pathogenic organisms or the toxins that they release that damage the tissues and organs are called immunity.
• The system that provides this immunity to fight against pathogens is called the immunity system.
• Antigens -
  • These are the foreign substances (pathogenic organisms or toxins) that invade the body and are capable of eliciting an immune response.
• Antibodies -
  • These are the chemicals produced by the immune system in response to the antigenic stimulus in the body.
  • They are also called immunoglobulins (Ig).
  • They fight against the antigens or the toxins and neutralize them.

Explanation:

Option 1 - INCORRECT

• ​The region of an antibody that binds with an antigen is known as a paratope.
• It is present in the variable region of the heavy and light chains of the immunoglobulin.
• These regions are characterized by an amino acid sequence that varies from one immunoglobulin to other and is associated with antigen-binding sites.
• Most antibodies carry two antigen-binding sites.

Option 2 - CORRECT

• ​Antigens are foreign bodies that when introduced into the body of an organism elicits an immune response and stimulate the production of antibodies.
• Most antigens are proteinaceous in nature. Some antigens may also be made up of carbohydrates.
• Epitopes or antigenic determinants are present on an antigen.
• These are the sites on antigens that are recognized by antibodies and receptors present on T and B cells.

 ​

Option 3 - INCORRECT

• ​Each antibody molecule is made up of four polypeptide chains.
• There are two long chains called Heavy chains or 'H' chains.
• The other two are short chains known as Light chains or 'L' chains.
• Heavy chains of an Ig help the antibody to be expressed on the surface of B cells due to its transmembrane domain.
• The variable region of the heavy chain contains the antigen binding site - paratope.

Option 4 - INCORRECT

• The ​V-region of the light chain of an antibody refers to the variable region of an antibody.
• It is present on both the heavy and light chains of Ig.
• It is associated with antigen-binding sites called paratopes. 
• Paratopes are the sites where an antibody binds with an antigen during the formation of an antigen-antibody complex.

So the correct answer is option 2.

The correct answer is C, D, E only

Concept:

• Lymphoid organs are the organs where the origin and/or maturation and proliferation of lymphocytes occur.
• The primary lymphoid organs are bone marrow and thymus, where immature lymphocytes differentiate into antigen-sensitive lymphocytes.
• After maturation, the lymphocytes migrate to secondary lymphoid organs like the spleen, lymph nodes, tonsils, Peyer’s patches of small intestine, and appendix.
• The secondary lymphoid organs provide the sites for interaction of lymphocytes with the antigen, which then proliferate to become effector cells.

Explanation:

• Spleen (C): The spleen filters blood and is a site where lymphocytes interact with blood-borne antigens. It plays a crucial role in immune responses to pathogens circulating in the bloodstream.
• Lymph Nodes (D): Lymph nodes are distributed throughout the body and filter lymph. They trap antigens from lymphatic fluid and allow interaction between lymphocytes and antigens, activating adaptive immune responses.
• Peyer’s Patches (E): Peyer’s patches are specialized mucosa-associated lymphoid tissues in the small intestine. They monitor intestinal contents for antigens and are essential for immune responses in the gut-associated lymphoid tissue (GALT).

Incorrect Options:

• Thymus (A): The thymus is a primary lymphoid organ responsible for the maturation of T cells. 
• Bone Marrow (B): The bone marrow is another primary lymphoid organ responsible for the development and maturation of B cells.

The correct answer is IgA

Explanation:

• Colostrum is the first form of milk produced immediately following the delivery of the newborn.
• It is rich in antibodies, especially IgA, which play a crucial role in providing immunity to the newborn during the first few days of life.
• IgA antibodies are essential for mucosal immunity and are found in high concentrations in colostrum.
• It plays a significant role in protecting the mucous membranes lining the respiratory and gastrointestinal tracts. By providing passive immunity, IgA helps to safeguard the newborn from infections during the early stages of life.

Other Options:

• IgG: While Immunoglobulin G (IgG) is the most common antibody in blood and extracellular fluid, providing long-term protection. IgG is mainly transferred to the newborn through the placenta during pregnancy.
• IgM: Immunoglobulin M (IgM) is the first antibody to respond to an infection and is primarily found in the blood and lymphatic fluid.
• IgE: Immunoglobulin E (IgE) is associated with allergic reactions and is found in very small amounts in the body. 

The correct answer is option 4.

Concept:

• The body's ability to fight disease-causing microbes is called immunity.
• There are two types of immunity: innate immunity and acquired immunity. 

Explanation:

Innate immunity

• It is present at the time of birth and is nonspecific in nature.
• It consists of four types of barriers:

Acquired immunity

• It is pathogen-specific and is acquired when our body is exposed to pathogenic microbes.
• It is based on memory. The T and B lymphocytes play a major role in acquired immunity.
• It is further classified as active and passive immunity.

So, the correct answer is option 4.

The correct answer is Passive immunization.

• If a person is infected with some deadly microbes to which quick immune response is required, we need to directly inject the preformed antibodies. This type of immunization is known as Passive immunization.
• Passive immunity: When ready-made antibodies are directly given to protect the body against foreign agents, it is called passive immunity.
• Active immunity: When a host is exposed to antigens, which may be in the form of living or dead microbes or other proteins, antibodies are produced in the host body. This type of immunity is called active immunity.

Active vs passive immunity

Key Points

• Inflammation is a signal when the body sends cells to defend against an irritant, an allergen, or a pathogen.
• The signs of inflammation include heat, redness in the skin, swelling, pain, etc.
• It is an important part of the body's immune system defenses.
• The cells involved in inflammatory reactions are basophils.
• Basophils are one of the granulocytes of white blood cells.
• The other two granulocytes are neutrophils and eosinophils.
• Basophils secrete histamine, serotonin, heparin, etc., and are involved in inflammatory reactions.
• Basophils contain cytoplasmic granules and the nucleus has two lobes.
• They play a role in both parasitic infections and allergies.

Additional Information

• Neutrophils:
  • These are granulocytes, a type of white blood cell.
  • Neutrophils are the most abundant cells (60-65
    percent) of the total WBCs.
  • Neutrophils are phagocytic cells that destroy foreign organisms entering the body.
• Eosinophils:
  • These are granulocytes, a type of white blood cell.
  • Eosinophils prevent infections and are also associated with allergic reactions.
• Lymphocytes:
  • These are agranulocytes, a type of white blood cell.
  • Lymphocytes are of two major types - B lymphocytes and T lymphocytes.
  • Both B and T lymphocytes are responsible for the immune responses of the body.

​​Hence, the correct option is (1) Basophils.

The correct answer is Passive immunization.

• If a person is infected with some deadly microbes to which quick immune response is required, we need to directly inject the preformed antibodies. This type of immunization is known as Passive immunization.
• Passive immunity: When ready-made antibodies are directly given to protect the body against foreign agents, it is called passive immunity.
• Active immunity: When a host is exposed to antigens, which may be in the form of living or dead microbes or other proteins, antibodies are produced in the host body. This type of immunity is called active immunity.

Active vs passive immunity