Leukocytes and Immune Response Quiz

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Questions and Answers

What is the primary role of major histocompatibility molecules (MHC) in the immune system?

To activate B and T cells (correct)

To break down foreign proteins

To transport oxygen in the blood

To signal the presence of pathogens

What characterizes agranular leukocytes?

They have multiple lobes in their nucleus.

They contain abundant cytoplasmic granules.

They have a single un-lobed nucleus and few granules. (correct)

They are primarily responsible for allergic reactions.

What role do dendritic cells play in the immune system?

They primarily kill bacteria.

They are the most numerous leukocytes in the blood.

They present antigens to T cells. (correct)

They are responsible for producing antibodies.

Mast cells and basophils are primarily involved in which type of immune response?

Allergic reactions Signup and view all the answers

What distinguishes HLA class I from HLA class II?

HLA class I is found on almost all nucleated cells Signup and view all the answers

What is the primary characteristic that distinguishes mature B cells from other lymphocytes?

Synthesis of membrane-bound immunoglobulin Signup and view all the answers

Which statement about monocytes is true?

They differentiate into macrophages after entering tissues. Signup and view all the answers

Which cluster of differentiation (CD) molecule supports the TCR and transduces signaling?

CD3 Signup and view all the answers

What is a significant feature of the MHC genes?

They are located on chromosome 6 Signup and view all the answers

Basophils are known for containing granules that have which type of substance?

Amines that affect smooth muscles Signup and view all the answers

Which statement best describes the size range of lymphocytes in the adaptive immune system?

Lymphocytes can range from 4 to 15 µm in size Signup and view all the answers

Which type of leukocyte is the most common in peripheral blood?

Neutrophils Signup and view all the answers

Which characteristic does not define class II HLA molecules?

They are only present on B cells Signup and view all the answers

What is a feature of eosinophils?

They play a role in responses to parasitic infections. Signup and view all the answers

Which of the following statements about T cell maturation is true?

Thymocytes undergo screening for self-recognition Signup and view all the answers

What is the primary function of neutrophils in the immune response?

Killing and digesting bacteria Signup and view all the answers

What role do cluster of differentiation (CD) molecules play in the adaptive immune system?

They indicate the functional capacities of various cells Signup and view all the answers

Which cells are formed as a result of naïve B cells encountering an antigen?

Effector cells and memory cells Signup and view all the answers

Which cell type is primarily responsible for recognizing antigens bound to MHC class II molecules?

CD4+ T cells Signup and view all the answers

What is the primary difference between plasma cells and memory B cells?

Plasma cells produce antibodies while memory B cells do not Signup and view all the answers

Which of the following best describes the polymorphism of MHC molecules?

They show variations in amino acid sequences among individuals Signup and view all the answers

Natural killer (NK) cells are characterized by the absence of which types of receptors?

TCR or BCR on their surfaces Signup and view all the answers

Which of the following is TRUE regarding CD8+ T cells?

They recognize MHC class I molecules Signup and view all the answers

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

To secrete large quantities of immunoglobulins Signup and view all the answers

What is the primary function of killer activation receptors (KARs) and killer inhibition receptors (KIRs)?

To distinguish between infected and healthy cells Signup and view all the answers

Which of the following statements about the thymus is correct?

More than 95% of thymocytes die by apoptosis before maturing. Signup and view all the answers

What occurs within the bone marrow regarding B cells?

A selection process eliminates B cells with self-reactive antibody receptors. Signup and view all the answers

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

To generate immune responses to antigens in lymph Signup and view all the answers

Which region of the lymph node primarily contains T lymphocytes?

Paracortex Signup and view all the answers

What is the role of the spleen in the immune system?

To filter blood and mount immune responses to antigens Signup and view all the answers

What changes occur in thymic function with age?

Thymic function declines, potentially reducing immune response. Signup and view all the answers

Which of the following structures are NOT considered secondary lymphoid organs?

Thymus Signup and view all the answers

Study Notes

Agranular Leukocytes

Monocytes spend 1-2 days in circulation before becoming macrophages in tissues
Both monocytes and macrophages contribute to phagocytosis
Dendritic cells, found in portals like the skin, engulf cells and particles
Dendritic cells mature after encountering antigens and present them to T cells, initiating adaptive immunity
Dendritic cells, macrophages, and B cells are all antigen-presenting cells (APCs)

Granular Leukocytes

Neutrophils make up the largest population (60%) of leukocytes and are effective at killing bacteria
Basophils and mast cells, both containing acidic granules, play a role in allergic reactions
Eosinophils are bilobed cells with granules containing basic proteins and are involved in parasitic infections

Major Histocompatibility Molecules (MHC)

MHC, also called the human leukocyte antigen (HLA) complex, is located on chromosome 6
MHC encodes enzymes and structural molecules necessary for B and T cell activation and function
MHC plays a critical role in determining tissue compatibility for transplants
MHC genes exhibit polymorphism, meaning they vary between individuals, impacting tissue compatibility

HLA Molecules

HLA class I molecules are expressed on almost all nucleated cells and bind to short antigenic peptides
HLA class II molecules are expressed on antigen-presenting cells (APCs) and bind to long antigenic peptides

Cluster of Differentiation Molecules (CD)

CD molecules serve as markers on leukocyte surfaces and indicate their functional capacities
CD3 supports the TCR and transmits signals when the TCR is engaged
CD4 is expressed on helper T cells (Th cells) and recognizes MHC class II complexes
CD8 is expressed on cytotoxic T cells (Tc cells) and recognizes MHC class I molecules

Lymphocytes

Lymphocytes are the major cells of the adaptive immune system, ranging in size from small to large
Lymphocytes can be categorized based on their receptors, site of training, and CD molecule expression

B lymphocytes (B cells)

B cells mature in the bone marrow and are defined by their expression of membrane-bound immunoglobulin (antibody) molecules
Upon encountering antigens, naïve B cells differentiate into plasma cells and memory cells
Plasma cells secrete large quantities of immunoglobulins for a short period

T lymphocytes (T cells)

T cells mature in the thymus and recognize antigens bound to MHC molecules
CD4+ T cells (helper T cells) recognize MHC class II complexes
CD8+ T cells (cytotoxic T cells) recognize MHC class I molecules and kill infected or cancerous cells

Natural Killer (NK) cells

NK cells lack TCRs or BCRs and are a unique subset of T cells, expressing TCRs and KIRs/KARs
NK cells can target virally infected cells and tumors

Immune System Organs ( Lymphatic System)

The lymphatic system consists of primary and secondary lymphoid organs
Primary lymphoid organs (thymus and bone marrow) are where lymphocyte maturation occurs
Secondary lymphoid organs (lymph nodes, spleen, and MALT) trap antigens and facilitate lymphocyte interaction with antigens

Thymus

The thymus selects against T cells that cannot recognize antigens or react with self-antigens
More than 95% of thymocytes die by apoptosis before reaching maturity
Thymic function declines with age, potentially contributing to weakened immunity

Bone Marrow

Bone marrow is the site of B cell origin and development
Bone marrow selects against B cells with self-reactive antibody receptors

Lymph Nodes

Lymph nodes are encapsulated structures containing lymphocytes, macrophages, and dendritic cells
They are sites of immune response to antigens in lymph
Lymph nodes are divided into the cortex, paracortex, and medulla, each with a distinct microenvironment

Spleen

The spleen mounts immune responses to antigens circulating in the bloodstream
It is a large, oval organ located in the left abdominal cavity

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Description

Test your knowledge on agranular and granular leukocytes, their functions, and the role of major histocompatibility molecules in the immune response. This quiz covers key aspects of immune cell types, their interactions, and contributions to adaptive immunity.