Antigen Presenting Cells and Dendritic Cells

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What characterizes effector cells in the immune response?

They only function in the bloodstream without tissue involvement.

They present antigens to other immune cells.

They actively engage in immune defenses after encountering antigens. (correct)

They are long-lived and store memory of antigens.

Which statement accurately describes professional antigen-presenting cells (APCs)?

They primarily provide signals to activate naïve T cells. (correct)

They require additional signals to activate effector B cells.

They are less effective at displaying antigens compared to non-professional APCs.

They can only present antigens during times of infection.

What is the role of Major Histocompatibility Complex (MHC) in antigen presentation?

MHC is responsible for activating B cells without T cell assistance.

MHC molecules destroy pathogens before they are presented.

MHC molecules help to attach antigens to the surface of APCs. (correct)

MHC facilitates the death of effector cells after antigen elimination.

Which type of immune cells are classified as naïve lymphocytes?

B-lymphocytes and T-lymphocytes that have not yet encountered foreign invaders. (C) Signup and view all the answers

How do non-professional APCs differ from professional APCs?

Non-professional APCs can only present antigens in specific situations. (A) Signup and view all the answers

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

Serving as a bridge between antigens and T cell activation (D) Signup and view all the answers

Which surface receptors do dendritic cells express upon activation?

Receptors for chemokines (A) Signup and view all the answers

What triggers the activation of dendritic cells?

Cytokines and Toll-like receptors (B) Signup and view all the answers

What happens to dendritic cells after they become activated?

They lose adhesiveness and migrate (A) Signup and view all the answers

What inflammatory cytokines are produced by activated dendritic cells?

Tumor Necrosis Factor and Interleukin-1 (B) Signup and view all the answers

Where are dendritic cells typically found in the body?

In lymphoid organs and epithelial tissues (D) Signup and view all the answers

Which type of dendritic cells migrate and are involved in B cell maturation?

Germinal center dendritic cells (D) Signup and view all the answers

What is the significance of chemokines in the function of dendritic cells?

They guide dendritic cells to lymph nodes (D) Signup and view all the answers

What is the primary role of dendritic cells during migration to lymph nodes?

They undergo maturation into antigen-presenting cells. (A) Signup and view all the answers

Which type of antigens do MHC class I molecules primarily present?

Intracellular and extracellular antigens (D) Signup and view all the answers

What is a critical function of professional antigen-presenting cells (APCs) like dendritic cells?

Efficient internalization of antigens through phagocytosis and endocytosis (D) Signup and view all the answers

How do dendritic cells interact with T cells after maturation?

By presenting antigens via MHC and expressing co-stimulatory molecules (C) Signup and view all the answers

What triggers the expression of MHC class II molecules on professional APCs?

Induced by cytokines and bacterial infection (B) Signup and view all the answers

Which cells are considered professional antigen-presenting cells?

Dendritic cells, macrophages, and B cells (D) Signup and view all the answers

Where are antigen-presenting cells primarily located in the body?

In connective and lymphoid tissues, and body cavities (C) Signup and view all the answers

Which co-stimulatory molecules are typically expressed by antigen-presenting cells?

B7 molecules (D) Signup and view all the answers

Which type of dendritic cells are specifically involved in capturing antigens from the skin and mucous surfaces?

Langerhans cells (A) Signup and view all the answers

What is the primary role of follicular dendritic cells (FDCs)?

Assisting in B cell maturation and antibody production (B) Signup and view all the answers

Which type of dendritic cells is rich in MHC class II molecules?

Interdigitating cells (A) Signup and view all the answers

Which characteristic is true about follicular dendritic cells (FDCs)?

They lack MHC class II molecules. (C) Signup and view all the answers

What is the primary function of dendritic cells when they interact with T cells?

They present antigens and activate T cells. (D) Signup and view all the answers

Which of the following is NOT a characteristic of interdigitating cells?

They do not interact with B cells. (D) Signup and view all the answers

Which of the following types of cells is considered a professional antigen-presenting cell (APC)?

Dendritic cells (B) Signup and view all the answers

How do germinal center dendritic cells assist in B cell function?

By helping form memory B cells. (A) Signup and view all the answers

What occurs when tissues are damaged and antigens are released?

The immune system mistakenly attacks the damaged tissues. (B) Signup and view all the answers

What is molecular mimicry in the context of autoimmunity?

Foreign antigens resemble the body's own proteins, leading to self-attack. (C) Signup and view all the answers

How can an alteration in antigen processing affect the immune system?

It might lead to the immune system attacking normal cells. (D) Signup and view all the answers

Which factor does NOT contribute to the development of autoimmunity?

Over stimulation of adaptive immunity. (A) Signup and view all the answers

What role do lymphocyte abnormalities play in autoimmunity?

They can lead to self-reactivity and autoimmunity. (C) Signup and view all the answers

What may happen due to the failure of central tolerance mechanisms?

Self-reactive lymphocytes persist and may attack the body. (A) Signup and view all the answers

Which of the following describes polyclonal lymphocyte activation?

Non-specific activation, including self-reactive lymphocytes. (D) Signup and view all the answers

How can chronic inflammation lead to autoimmunity?

By disrupting immune system’s tolerance to self-antigens. (A) Signup and view all the answers

Study Notes

Antigen Presenting Cells (APCs)

APCs are immune cells that display antigens on their surface, alerting other immune cells to an infection.
APCs can be divided into two groups:
- Professional APCs: These are cells specialized for presenting antigens, including dendritic cells, macrophages, and B cells. They are highly efficient at antigen presentation and activating naive T cells.
- Non-professional APCs: These cells can also present antigens but only under specific circumstances, such as during an infection. They are less effective at antigen presentation compared to professional APCs.
Professional APCs are important because they:
- Display antigens on their surface for T cells to recognize.
- Provide signals necessary to fully activate naive T cells.

Types of Dendritic Cells

Langerhans cells: Found in the skin and mucosal epithelium. Capture antigens from these surfaces and migrate to lymph nodes to trigger an immune response.
Interdigitating cells: Dendritic cells that travel to lymphoid tissues (like lymph nodes) and interact with T cells. They help activate T cells by presenting antigens.
Follicular dendritic cells (FDCs): Found in the primary and secondary follicles of B cell areas in lymph nodes and the spleen. Present antigens to B cells to aid in antibody production.
Germinal center dendritic cells (GCDC): Found within germinal centers. Assist in B cell maturation and the selection of high-affinity antibodies, forming memory B cells.

Dendritic Cell Migration and Maturation

When dendritic cells encounter an antigen, they activate and undergo various changes:
- Loss of adhesiveness to the epithelial tissue.
- Expression of specific surface receptors that respond to chemokines.
- Migration to lymph nodes guided by chemokines.
As dendritic cells mature, they express MHC and co-stimulatory molecules for efficient interaction and activation of T cells.

MHC Expression in Professional APCs

Macrophages: MHC-II expression is induced by bacteria and/or cytokines. MHC-I is expressed at low levels.
Dendritic Cells: MHC-II is expressed constantly and at high levels. MHC-I is expressed at low levels but is induced by bacteria and/or cytokines.
B Cells: MHC-II is always expressed and is further induced upon activation. MHC-I is constantly expressed at low levels.

Antigen Presentation by Professional APCs

Macrophages: Process both intracellular and extracellular antigens. Antigens are presented via MHC-II (extracellular antigens) and MHC-I (intracellular).
Dendritic Cells: Process extracellular antigens. Antigens are presented via MHC-II.
B Cells: Process extracellular antigens that bind to specific immunoglobulin receptors. Antigens are presented via MHC-II.

Co-stimulation

Co-stimulatory molecules (like B7 expression) are necessary for full T cell activation. B7 expression is induced by bacteria and/or cytokines in macrophages. In dendritic cells, B7 is always expressed at high levels. B7 expression in B cells is induced upon activation.

Location of Professional APCs

Macrophages: Found in connective tissues, lymphoid tissues, body cavities, and blood.
Dendritic Cells: Located in the connective tissue, epithelium, and lymphoid tissues.
B Cells: Found in lymphoid tissues and blood.

Autoimmunity

Autoimmunity occurs when the immune system mistakenly attacks the body's own tissues and organs.
Mechanisms of autoimmunity:
- Tissue damage: Damaged tissue releases antigens that are mistaken for foreign invaders.
- Molecular changes: Self-proteins may undergo structural changes and be recognized as foreign.
- Molecular mimicry: Foreign antigens resemble self-proteins, leading to cross-reactivity.
- Alteration in antigen processing: Defects in antigen processing can lead to improper recognition of self-antigens.
- Infection: Certain infections can disrupt tolerance to self-antigens.
- Genetic factors: Specific genes can increase susceptibility to autoimmune diseases.
Other contributing factors:
- Lymphocyte abnormalities: Abnormal B or T cells can contribute to autoimmunity.
- Failure of central tolerance: Self-reactive lymphocytes fail to be eliminated in the thymus or bone marrow.
- Overcome of peripheral tolerance: Mechanisms that suppress self-reactive lymphocytes fail.
- Polyclonal lymphocyte activation: Non-specific activation of lymphocytes, potentially including self-reactive ones, can lead to autoimmunity.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Description

Explore the essential roles of antigen presenting cells (APCs) in the immune response, including the distinction between professional and non-professional APCs. Gain insights into the specific types of dendritic cells, such as Langerhans cells, and their functions in triggering immunity. Test your understanding of these key concepts in immunology.