Immunology Overview Quiz

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Questions and Answers

Which cell type is primarily responsible for preventing overactive immune responses?

Suppressor T cell (correct)

Helper T cell

Cytotoxic T cell

Plasma cell

Which T cell type is mainly involved in destroying cells infected by viruses or causing transplant rejection?

Helper T cell

Cytotoxic T cell (correct)

Suppressor T cell

Memory T cell

What characterizes innate immunity?

It requires previous exposure to pathogens.

It is present from birth and protects against a variety of pathogens. (correct)

It specifically targets a narrow range of pathogens.

It is a learned response that improves with time.

What is the role of phagocytes in the immune response?

They engulf and digest pathogens and debris. Signup and view all the answers

In which site do T cells typically become activated after recognizing antigens?

Lymph node Signup and view all the answers

What is the primary function of MHC molecules in T cell activation?

To present foreign antigens to T cells Signup and view all the answers

Which of the following statements about adaptive immunity is correct?

It remembers previous encounters with pathogens. Signup and view all the answers

Which statement about class-2 MHC molecules is incorrect?

They are involved in activating Cytotoxic T cells Signup and view all the answers

Which cells are primarily responsible for the first response to infection?

Neutrophils Signup and view all the answers

What role do Helper T cells play in the immune response?

Secrete proteins to assist other immune cells Signup and view all the answers

What is the main function of interferons in the immune system?

To inhibit viral replication. Signup and view all the answers

Which process allows phagocytes to move out of capillaries to reach the site of infection?

Diapedesis Signup and view all the answers

How does adaptive immunity differ from innate immunity?

Adaptive immunity provides memory against previously encountered pathogens. Signup and view all the answers

What mechanisms are included in the innate immune defense?

Epithelial barriers and inflammation. Signup and view all the answers

Which of the following is NOT a characteristic of adaptive immunity?

It is limited to local infection sites. Signup and view all the answers

What is the primary role of B cells in the immune response?

To produce antibodies that tag antigens Signup and view all the answers

What do memory cells do upon re-exposure to the same antigen?

Initiate a rapid and potent immune response Signup and view all the answers

What occurs during the primary response to a pathogen?

Latent period followed by antibody production Signup and view all the answers

What type of cells do T cells become after sensitization?

Helper T cells and cytotoxic T cells Signup and view all the answers

How do antibodies function in the immune response?

By enhancing the activity of complement proteins Signup and view all the answers

What establishes the specificity of antibodies?

The differences in their basic structure Signup and view all the answers

What is the role of the complement system?

To amplify the action of antibodies against pathogens Signup and view all the answers

What type of antigens do B cells typically recognize?

Proteins and sugars of foreign entities Signup and view all the answers

During the activation of B cells, they can differentiate into which two types of cells?

Plasma cells and memory cells Signup and view all the answers

What is the structure of an antibody primarily characterized by?

A common framework with unique variable regions Signup and view all the answers

Study Notes

Learning Objectives

Compare and contrast innate and adaptive immunity
Describe the role of T cells and B cells in immunity
Describe local inflammation

Innate Immunity (Nonspecific)

Local response to protect against pathogens and toxins
Born with these defenses; no prior exposure needed
Does not discriminate the type of pathogen involved (bacteria, viruses, dust, bugs)
Includes external and internal defenses (epithelial barriers, high acidity of secretions, phagocytosis, inflammation, fever)

Nonspecific Phagocytosis

Neutrophils are the first to arrive at an infection site.
Macrophages are phagocytes in specific organs (liver, spleen, lymph nodes, lungs, brain)
They line sinusoids to remove pathogens.
Chemokines attract phagocytes via chemotaxis.
Phagocytes exit capillaries via diapedesis through fenestrations.

Interferons

Polypeptides produced by virus-infected cells
Provide resistance to viral infection in nearby cells
Inhibit the virus's ability to replicate and assemble new virus particles

Adaptive Immunity (Specific)

Acquired ability to fight specific pathogens after prior exposure.
Also called the learned response
Systemic; not restricted to a local infection site
Has memory; mounts a stronger attack upon encountering previously encountered pathogens

Two Types of Adaptive Immunity

Cell-mediated: T cells present antigens to killer cells. These killer cells attack infected host cells, cancer cells, and foreign cells.
Antibody-mediated: B cells create antibodies to tag antigens for destruction. These antibodies attack bacteria and viruses.

Life of a B Cell

Develops from a stem cell in bone marrow; sometimes stays there.
Becomes a mature B cell (gains receptors).
Enters lymph and blood (humoral).
Encounters an antigen (becomes activated)
Differentiates into plasma cells (make antibodies) and memory cells (for future exposure)

B Lymphocytes

B cells have receptors to recognize diverse foreign antigens, usually proteins from viruses, bacteria, or allergens.
After recognizing a matching antigen, B cells divide and produce clones.
Differentiate into plasma cells or memory cells

Life of a T Cell

Develops from a bone marrow stem cell.
Moves to the thymus to mature and gain receptors.
Proceeds to lymph and blood
Meets an antigen (becomes sensitized).
Differentiates into helper T cells, cytotoxic T cells, or suppressor T cells.

T Lymphocytes

Cell-mediated immunity
Mature in the thymus
Activated by antigen-presenting cells (e.g., macrophages, dendritic cells, B cells)
Activated T cells promote macrophage and lymphocyte action.

Types of T Cells

Helper T cell (CD4): About 60-80% of T cells; secrete proteins to support other parts of the immune system (e.g., B cell growth factor and interleukins).
Suppressor/Regulatory T cell: Prevents overactive immune responses.
Cytotoxic/Killer T cell (CD8): Releases perforin to create pores in foreign cells, causing osmosis and destruction. Defends against viruses, fungi, and participates in transplant rejection.

Primary and Secondary Responses

Primary Response: On first exposure to pathogens, there's a 5-10 day latency before specific antibodies are produced, plateau, and decline.
Secondary Response: Subsequent exposure to the same antigen triggers a much faster and sustained antibody production.

Antibodies (Immunoglobulins)

Proteins belonging to the gamma globulin class in plasma.
Have a consistent basic structure, but differences in their components determine specificity.

Complement

Enhances the actions of antibodies.
Activated by pathogens (nonspecific) or antibodies (specific).
Proteins form a pore (membrane attack complex, MAC) in the foreign cell, leading to osmotic water influx and cell lysis.

Memory Cells

Remembers previous exposure to specific antigens.
The primary and secondary responses highlight memory cells' impacts.
Responds much faster and more effectively with a secondary response.

MHC Molecules

Class I MHC molecules are found on all cells and signal to killer cells about infected cells
Class II MHC molecules are found on antigen-presenting cells and signal to helper T cells about foreign invaders.

Interaction Between Cells

The interaction between MHC molecules and helper or killer T cells is essential to activating the cellular and humoral arms of the immune response.

Review Questions and Answers

Question: Which cell type shuts down immune response after infection?
Answer: Suppressor T cells

Self-Antigens

Human cells have unique surface proteins (self-antigens).
Immune cells normally don't attack self-antigens.
Foreign antigens trigger immune responses (e.g., transplant rejection).

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Description

This quiz covers key concepts in immunology, including the differences between innate and adaptive immunity, as well as the roles of T cells and B cells. Additionally, it explores the process of local inflammation and the function of phagocytes in the immune response.