Immunology Chapter: Innate vs Adaptive Immunity

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Questions and Answers

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

Suppressor T cell (correct)

Helper T cell

Cytotoxic T cell

B lymphocyte

Which statement about the activation of T cells is accurate?

Helper T cells are only activated by cytotoxic T cells.

T cells can be activated without MHC molecules.

Cytotoxic T cells require assistance from Helper T cells for activation. (correct)

Antigens can activate any T cell regardless of their type.

What role do MHC molecules play in the immune response?

They are responsible for the destruction of virus-infected cells.

They enhance the osmosis process in foreign cells.

They assist in the maturation of B cells.

They present antigens to T cells, thus activating specific T cell responses. (correct)

Which type of T cell is most abundant in the immune system?

Helper T cell Signup and view all the answers

In the context of transplantation, what triggers an immune response?

Foreign antigens presented by the recipient's MHC. Signup and view all the answers

Which of the following statements about class-2 MHC molecules is correct?

They are involved in presenting foreign antigens to Helper T cells. Signup and view all the answers

What is the primary function of plasma cells in the immune response?

To produce antibodies Signup and view all the answers

During which immune response do memory cells become crucial for a faster reaction?

Secondary response Signup and view all the answers

Which cell type is responsible for attacking infected host cells, cancer cells, and foreign cells?

Cytotoxic T cells Signup and view all the answers

What happens during the primary response to a pathogen?

Latency before antibody production Signup and view all the answers

What characteristic distinguishes antibodies from one another?

The specificity in their variable regions Signup and view all the answers

What role does the complement system play and how is it activated?

It aids in bacterial cell lysis; activated by pathogens or antibodies Signup and view all the answers

What is the correct sequence for the development of T cells?

Bone marrow → Thymus → Lymph Signup and view all the answers

How do B cells initially recognize foreign antigens?

Via antigen receptors on their surface Signup and view all the answers

In what way does the humoral immune response differ from the cell-mediated response?

It involves antibodies produced by B cells Signup and view all the answers

What effect does the membrane attack complex (MAC) have on a target cell?

It causes the cell to swell and burst Signup and view all the answers

What characterizes innate immunity as discussed?

It can recognize and respond to a variety of pathogens. Signup and view all the answers

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

Operates without any prior knowledge of pathogens. Signup and view all the answers

Which cells are typically the first to respond to an infection during the innate immune response?

Neutrophils Signup and view all the answers

What process describes the attraction of phagocytes to the site of infection?

Chemotaxis Signup and view all the answers

Which statement about macrophages is true?

They are organ-specific phagocytes found in various tissues. Signup and view all the answers

What role do interferons play in the immune response?

They provide resistance against viral infections in neighboring cells. Signup and view all the answers

What is the main difference between innate and adaptive immunity?

Innate immunity is present at birth, while adaptive immunity develops after exposure. Signup and view all the answers

Which of the following best describes 'specific defense systems'?

They are activated only after pathogen exposure. Signup and view all the answers

What is the purpose of diapedesis in the immune response?

To facilitate movement of phagocytes through blood vessels. 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
Protects against a wide variety of pathogens and toxins
Present from birth
Doesn't differentiate between types of pathogens (e.g., bacteria, viruses, dust, bugs)
Includes external and internal defenses
Epithelial barriers
High acidity of secretions
Phagocytosis
Inflammation, fever

Nonspecific Phagocytosis

Neutrophils: First to arrive at an infection site
Macrophages: Organ-specific phagocytes in liver, spleen, lymph nodes, lungs, and brain.
- Line sinusoids of liver, spleen, and lymph nodes to remove pathogens.
- Chemokines released from tissue attract phagocytes through a process called chemotaxis
- Phagocytes move out of capillaries through fenestrations via diapedesis

Interferons

Polypeptides produced by cells infected with a virus
Provide resistance to viral infections in nearby cells
Inhibit the ability of a virus to replicate and assemble new virus particles

Adaptive Immunity (Specific)

Acquired ability to defend against specific pathogens by prior exposure
Also known as the learned response
Systemic: Not restricted to a local infection site
Has memory: Recognizes and mounts a stronger attack on previously encountered pathogens

Two Types of Adaptive Immunity

Cell-mediated: Uses T cells to present antigens to killer cells
- Attacks infected host cells (viruses, fungi), cancer cells, and foreign cells
Antibody-mediated: Uses B cells to make antibodies to tag antigens for death
- Attacks bacteria and viruses

Life of a B Cell

Begins as a stem cell in bone marrow
Maturation/stays in bone marrow
Mature B cell (gains receptors)
Enters the lymph and blood (humoral)
Exposed to antigen
Activated B cell
- Plasma cells: Make antibodies
- Memory cells: For second exposure

B Lymphocytes

B cells have receptors to identify foreign antigens, which are usually proteins from foreign viruses, bacteria, and allergens
After recognizing the matching antigen, B cells undergo division forming a clone
B cells develop into plasma cells or memory cells

Antibodies

AKA immunoglobulins (proteins)
Part of the gamma globulin class of plasma proteins
Have a similar basic structure but differences provide for antibody specificity

Complement

Complements the action of antibodies
Activated by pathogens (nonspecific) or exposure to antibodies (specific)
When activated, proteins build a pore in the foreign cell, which is called the membrane attack complex (MAC)
Osmotic influx of water, cell swells, and bursts

B Cells and T Cells

Stem cell → Antigen → B lymphocyte/T lymphocyte
B cells produce antibodies, while cytotoxic T cells destroy infected cells
T cells involved need help from helper T cells which activate the B and cytotoxic T cells

Life of a T Cell

Begins as a stem cell in bone marrow.
Travels to the thymus.
Develops into a mature T cell with receptors.
Enters lymph and blood.
Exposed to an antigen
Develops into a sensitized T cell:
Helper T cell
Cytotoxic T cell
Suppressor T cell

T Lymphocytes

Cell-mediated immunity
Mature in thymus
Activated by antigens presented by antigen-presenting cells
- Examples: macrophages, dendritic cells, B lymphocytes
T cells activated promote action of macrophages and lymphocytes

Types of T Cells

Helper T cell (CD4):
- 60-80% of T cells
- Secretes proteins to assist other systems
- B cell growth factor
- Interleukins for T cell growth
Suppressor/regulatory T cell:
- Prevents overactive immune responses

Cytotoxic/Killer T Cell (CD8)

Releases perforin to create a pore in foreign cells
Causes osmosis and destruction of the infected cell
Involved in transplant rejection, defending against viruses, and fungi

MHC Molecules

Occur in lymph nodes
Found on all cells
Signals infected cells

Interaction between Class-2 MHC & Helper T cell

Occurs in lymph nodes
Macrophage presents antigen to cells

Primary and Secondary Responses

Primary response (1st exposure): Latency of 5-10 days before specific antibodies are made
Antibody levels plateau, decrease after a few weeks
Secondary response (Subsequent exposure): Antibody production is more rapid and sustained

Self-Antigens

Human cells have surface proteins (self-antigens)
Immune cells typically do not attack self-proteins
Foreign cell proteins can trigger an immune response. This aspect is important in organ transplant rejection.

T cells recognize MHC

The pathogen is taken in by a phagocyte
A protein is put into a membrane called MHC
MHC molecules on cell membranes come in different combinations.
T cells recognize MHC plus antigen
Activates specific T cell response to specific antigens

Questions of the Day

Explain how antibodies help destroy invading bacterial cells.
Describe the interaction between the antigen-presenting cell and T cell
Compare and contrast B and T lymphocytes

Autoimmune Diseases

Failure of the immune system to tolerate self-antigens
Formation of autoreactive T cells and B cells.
Production of autoantibodies (e.g., Myasthenia Gravis, antibodies to nicotinic cholinergic receptors on skeletal muscle).

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Description

Test your understanding of innate and adaptive immunity in this quiz. Compare their roles, particularly the functions of T cells and B cells. Additionally, explore key concepts such as local inflammation and the process of phagocytosis.