Immune Response and Cell Functions

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Questions and Answers

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

Phagocytize foreign substances

Produce antibodies to immobilize antigens

Manage the immune response and destroy foreign cells (correct)

Capture antigens and transport them to lymph nodes

Which of the following correctly describes B cells?

They help activate macrophages.

They transport antigens to the thymus.

They secrete antibodies through plasma cells. (correct)

They directly destroy foreign cells.

What role do macrophages play in the immune response?

They capture antigens for transport back to the thymus.

They produce antibodies.

They form a stroma for other immune cells.

They phagocytize foreign substances and activate T cells. (correct)

Which of the following statements about primary lymphatic organs is true?

They are sites where stem cells become immunocompetent. Signup and view all the answers

Which cells are involved in capturing antigens and bringing them back to the lymph nodes?

Dendritic cells Signup and view all the answers

What is the primary function of the macrophages within the red pulp of the spleen?

Remove ruptured or defective blood cells Signup and view all the answers

Which component of the spleen is responsible for immune function and contains lymphocytes?

White pulp Signup and view all the answers

What percentage of the body’s platelet supply can the spleen store?

1/3 Signup and view all the answers

Which of the following functions of the spleen does NOT typically occur after birth?

Fetal erythrocyte production Signup and view all the answers

What constitutes the stroma of the spleen?

Capsule, trabeculae, reticular fibers, and fibroblasts Signup and view all the answers

What is the process called when neutrophils squeeze through the blood vessel wall to reach damaged cells?

Emigration Signup and view all the answers

What type of immunity involves B cells transforming into plasma cells that produce antibodies?

Antibody-mediated immunity Signup and view all the answers

Which cells are transformed from monocytes and are more potent than neutrophils?

Macrophages Signup and view all the answers

What characterizes adaptive immunity in contrast to innate immunity?

Memory Signup and view all the answers

Which of the following statements about T cells is true?

T cells mature in the thymus Signup and view all the answers

What is the primary role of helper T cells in the immune response?

Regulate activity of B cells and cytotoxic T cells Signup and view all the answers

What type of pathogens are cytotoxic T cells primarily effective against?

Intracellular pathogens Signup and view all the answers

What forms a pocket of dead phagocytes and damaged tissue?

Pus Signup and view all the answers

What is the primary function of lymph nodes in the immune system?

To filter foreign substances and activate an immune response Signup and view all the answers

Which cells are primarily located in the outer cortex of a lymph node?

B cells forming lymphatic nodules Signup and view all the answers

What is the role of dendritic cells in the lymph node?

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

How does lymph flow through a lymph node?

In one direction only, entering through afferent vessels Signup and view all the answers

Which component of the lymph node is primarily responsible for its structural support?

Stroma Signup and view all the answers

What do the medullary sinuses in the lymph node do?

Drain lymph towards efferent lymphatic vessels Signup and view all the answers

What are the two distinct regions of a lymph node?

Cortex and medulla Signup and view all the answers

Which type of lymphocytes are primarily found in the deep cortex of a lymph node?

T cells Signup and view all the answers

What is the main function of clonal selection in lymphocytes?

To proliferate and differentiate in response to a specific antigen Signup and view all the answers

Which type of cells arise from clonal selection specifically to respond to a secondary invasion?

Memory cells Signup and view all the answers

What are the two main characteristics of antigens?

Immunogenicity and reactivity Signup and view all the answers

Which part of an antigen is primarily responsible for triggering a response in the immune system?

Epitopes or antigenic determinants Signup and view all the answers

What is the role of Major Histocompatibility Complex (MHC) antigens?

To help T cells recognize both foreign and self-proteins Signup and view all the answers

In which organs and tissues does clonal selection primarily take place?

Secondary lymphatic organs and tissues Signup and view all the answers

Which of the following is NOT a type of effector cell produced during clonal selection?

Naïve T cell Signup and view all the answers

What role does the complement system play in the immune response?

Causes cytolysis of microbes and enhances inflammation. Signup and view all the answers

How does the immune system's diversity in antigen receptors benefit the body?

It allows recognition of a vast array of different pathogens Signup and view all the answers

Which of the following proteins is NOT involved in binding iron in the body?

Albumin Signup and view all the answers

What is the primary function of antimicrobial proteins (AMPs)?

Exhibit antimicrobial activity and attract immune cells. Signup and view all the answers

Which characteristic is unique to Natural Killer (NK) cells?

They can kill abnormal body cells without previous sensitization. Signup and view all the answers

What is one of the first steps in the process of phagocytosis?

Chemotaxis of phagocytes towards microbes. Signup and view all the answers

Which phase of inflammation is characterized by increased blood flow and permeability to remove debris?

Vasodilation. Signup and view all the answers

During inflammation, what substances are allowed to pass out of the blood due to increased permeability?

Antibodies and clotting factors. Signup and view all the answers

What is one of the signs of inflammation?

Swelling. Signup and view all the answers

What mechanism allows phagocytes to attach to abnormal or infected cells?

Adhesion. Signup and view all the answers

What best describes the role of the phase called 'emigration' in inflammation?

Phagocytes migrating to the site of infection. Signup and view all the answers

Study Notes

Lymphatic System

The lymphatic system is a network of vessels, tissues, and organs that helps maintain fluid balance in the body and plays a crucial role in immunity.
It consists of lymph, lymphatic vessels, structures and organs containing lymphatic tissue, and red bone marrow.
The lymphatic system functions to drain excess interstitial fluid, transport dietary lipid, and carry out immune responses.

Immunity or Resistance

Immunity is the body's ability to ward off damage or disease.
Two types are present, innate (non-specific) and adaptive (specific).
Innate immunity is present at birth and involves no specific recognition of invaders, and no memory component.
Adaptive immunity is based on specific recognition of invaders with a memory component of previous exposure to a pathogen.

Lymphatic Vessels and Lymph Circulation

Lymphatic vessels begin as lymphatic capillaries, which are closed at one end.
These capillaries collect excess interstitial fluid, which becomes lymph.
Lymphatic vessels unite to form larger vessels similar in structure to veins but with thinner walls and more valves.
Lymphatic vessels pass through lymph nodes and encapsulated organs containing masses of B and T cells.

Lymphatic Capillaries

Lymphatic capillaries are slightly larger in diameter than blood capillaries.
They have a unique one-way structure that permits interstitial fluid to flow into them but not out.
Anchoring filaments help widen the openings when interstitial fluid accumulates.

Lymph Trunks and Ducts

Lymphatic vessels unite to form lymph trunks.
The principal trunks are lumbar, intestinal, bronchomediastinal, subclavian, and jugular.
Lymph from the trunks flows into two main channels – thoracic and right lymphatic ducts.
These ducts empty the lymph into the venous blood.

Lymphoid Cells

Lymphocytes are the main cells involved in the immune response and come in two main varieties: T cells and B cells.
T cells manage the immune response and destroy foreign cells.
B cells produce plasma cells, which secrete antibodies that immobilize antigens.
Other lymphoid cells include macrophages (phagocytize foreign substances and help activate T cells), dendritic cells (spiny-looking cells similar to macrophages that capture antigens and bring them back to lymph nodes), and reticular cells (fibroblast-like cells that produce a stroma supporting other cell types in lymphoid organs).

Lymphatic Tissues and Organs

Lymphatic tissues and organs are grouped into two categories based on their function.
Primary lymphatic organs are sites where stem cells divide and become immunocompetent to produce a normal immune response (red bone marrow and thymus).
Secondary lymphatic organs are sites where most immune responses occur (lymph nodes, spleen, lymphatic nodules).

Lymphoid Organs

Lymphoid organs include the thymus, lymph nodes, spleen and lymphatic nodules.
Tonsils are in the pharyngeal region and Thymus is located in the thorax and most active during youth.
Spleen curves around the left side of the stomach.
Peyer's patches are in the intestine, and the appendix.
The thymus is important in T-lymphocyte maturation.

Thymus

The thymus contains an outer cortex and inner medulla.
The cortex has densely packed lymphocytes and scattered macrophages.
The medulla contains fewer lymphocytes and thymic corpuscles.
The thymus is different from other lymphoid organs.
It functions strictly in T lymphocyte maturation and does not directly fight antigens.

Lymph Nodes

Lymph nodes are located along lymphatic vessels, scattered throughout the body.
The stroma supports the connective tissue.
The parenchyma is the functional part of the node with an outer cortex containing B cells (lymphatic nodules) where plasma cells and memory B cells form, and an inner cortex comprised of T cells and dendritic cells, and a medulla containing B cells, antibody-producing plasma cells from the cortex, and macrophages.

Spleen

The spleen is the largest single mass of lymphatic tissue in the body.
It has stroma consisting of a capsule, trabeculae, reticular fibers, and fibroblasts.
The spleen contains white pulp, which contains lymphocytes and macrophages, and red pulp, which has blood-filled venous sinuses, splenic cords, red blood cells, macrophages, lymphocytes, plasma cells, and granulocytes.
Macrophages in the spleen remove ruptured, worn-out, or defective blood cells.

Lymphatic Nodules

Lymphatic nodules are scattered throughout the lamina propria of mucous membranes lining various parts of the body, such as the gastrointestinal, urinary, and reproductive tracts.
They are also part of the mucosa-associated lymphatic tissue (MALT) of the respiratory tract.
Some are small and solitary, while others are larger, such as tonsils, Peyer's patches, and the appendix.

Antigen Processing

B cells can recognize and bind to antigens in lymph, interstitial fluid, or blood plasma, whereas T cells only recognize processed antigen fragments presented in a specific way.
Antigenic proteins are broken into peptide fragments, and are associated with MHC molecules.
This antigen-MHC complex is inserted into the plasma membrane for T cell binding.

Antigen Presenting Cells (APCs)

Antigen presenting cells (APCs) include macrophages, dendritic cells, and B cells.
APCs process and present the antigen, which can penetrate various tissues—skin (Langerhans cells), mucous membranes of various tracts such as respiratory, gastrointestinal, urinary, and reproductive, and lymph nodes.

Exogenous and Endogenous Antigens

Exogenous antigens are present in fluids outside the body cells (e.g., bacteria, toxins, viruses).
APCs ingest, process, and place the processed antigen next to MHC-II molecules in their plasma membranes, presenting the antigen to T cells.
Endogenous antigens are found inside the cell (e.g., infected body cells; cancer cells).
Infected cells display the antigen fragments next to MHC-I molecules for T cell recognition.

Cell-mediated Immunity

Cytotoxic T cells attack and destroy invading antigens.
These cells are particularly effective against intracellular pathogens like viruses, some cancer cells, and foreign tissue transplants.
T cells are activated by a combination of signaling and costimulation. Anergy (lack of response) can also occur.

Helper T Cell Activation and Clonal Selection

Helper T cells (CD4+ T cells) recognize and bind to antigen fragments associated with MHC-II molecules.
Activation leads to clonal selection of helper T cells, producing both active helper T cells and memory helper T cells.
Activation and clonal selection involve costimulation with interleukin-2 (IL-2).

Cytotoxic T Cell Activation and Clonal Selection

Cytotoxic T cells (CD8+ T cells) recognize antigen presented with MHC-I molecules.
Activation leads to clonal selection and the creation of active cytotoxic T cells and memory cytotoxic T cells.

Elimination of Invaders

Cytotoxic T cells migrate and destroy infected target cells through granzymes inducing apoptosis (cell death) or using perforins, and granulysin for direct cell lysis (cell bursting).
Macrophages and natural killer (NK) cells also contribute to the eradication of infected cells.
Tumour antigens, displayed on cancerous cells, may also be targeted for destruction by cytotoxic T cells.

Antibody-Mediated Immunity

B-cell activation requires antigen binding to BCRs.
Antigen processing and costimulation by helper T cells result in the development of plasma cells and memory B cells, which produce and release antibodies targeting and neutralizing extracellular pathogens.

Antibodies

Antibodies are glycoproteins that bind to specific epitopes of antigens that triggered their production. They belong to a group of glycoproteins called antibodies, or immunoglobulins (Igs).
Antibodies consist of four polypeptide chains—two heavy and two light chains. The variable regions (at the tips of the "Y" shape) of the chains allow for antigen-specific binding, while the constant region (remainder of the chains) determines the type of antibody response.

Immunological Memory

The body develops memory cells after the first encounter with an antigen. This allows for a faster and more intense response to subsequent exposure to the same antigen. The amount of antibodies (antibody titer) in serum can be measured as a measure of immunological memory.

Self-Recognition and Self-Tolerance

T cells must be capable of recognizing self-MHC proteins.
T cells that cannot recognize self-MHC molecules undergo apoptosis.
Self-tolerance develops through negative selection, eliminating T and B cells that recognize self-peptide fragments. Anergy occurs when cells don't respond to self antigens, becoming unresponsive.

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Description

This quiz delves into the critical roles of T cells, B cells, and macrophages in the immune response. You'll explore the functions of various immune components, including the spleen's role in immunity and blood cell dynamics. Test your understanding of essential concepts in immunology through a series of thought-provoking questions.