WBCs: Lymphocytes

Questions and Answers

Which of the following is NOT a characteristic of the innate immune response?

Non-specific

Fast

Generic

Specific (correct)

Which cells are primarily involved in phagocytosis within the innate immune system?

Lymphocytes

B cells

Neutrophils (correct)

T cells

Which of the following immune cells is responsible for immunological surveillance?

Dendritic Cells

Natural Killer Cells (correct)

B cells

T cells

What are the classical signs of inflammation?

Rubor, calor, dolor, tumor Signup and view all the answers

Which natural antimicrobial substance is NOT part of the innate immune system?

Antibodies produced by B cells Signup and view all the answers

What type of immunity is dependent on the recognition of specific antigens?

Antigen-Specific Immunity Signup and view all the answers

Which of the following cells is NOT classified as an innate immune cell?

B cells Signup and view all the answers

Which of the following physical barriers provides defense at body surfaces?

Epithelial membranes Signup and view all the answers

What is the primary function of memory B cells?

To confer immunological memory Signup and view all the answers

Which characteristic is true for memory B cells?

They have undergone 'class switch' in development. Signup and view all the answers

What is the correct statement about plasma cells?

Plasma cells are specialized for rapid antibody secretion. Signup and view all the answers

Which of the following is true about T-cells?

T-cells help protect against intracellular pathogens. Signup and view all the answers

Which statement accurately describes the role of antibodies?

They enhance phagocytosis through opsonization. Signup and view all the answers

What is the presence of CD19 on B-cells indicative of?

They are B-cells. Signup and view all the answers

What is the primary role of B lymphocytes in the immune system?

Production of antibodies Signup and view all the answers

Which type of T cells primarily recognize MHC-II molecules?

CD4+ T helper cells Signup and view all the answers

What process happens at the cortex-medulla border of the thymus?

Negative selection leading to apoptosis of self-reactive thymocytes Signup and view all the answers

What percentage of thymocytes typically die by apoptosis before reaching maturity?

95-98% Signup and view all the answers

Which characteristic do CD8+ T cytotoxic cells express?

CD8 glycoproteins Signup and view all the answers

How do CD8+ T cytotoxic cells eliminate infected cells?

By apoptosis Signup and view all the answers

What is one of the key functions of interferon-gamma (IFN-γ) secreted by CD8+ T cells?

Limits viral replication and infection spread Signup and view all the answers

What is the primary function of the thymus in relation to T-cells?

Development and selection of T-cells Signup and view all the answers

What role do antigen-presenting cells (APCs) play in T cell activation?

They present antigens via MHC molecules Signup and view all the answers

Which of these lymphocyte types is specifically involved in humoral immunity?

B lymphocytes Signup and view all the answers

Which type of lymphocytes is primarily responsible for producing antigen-specific antibodies?

B lymphocytes Signup and view all the answers

What distinguishes cell-mediated immunity from humoral immunity?

Direct killing of infected cells Signup and view all the answers

What is the normal range of lymphocytes in the blood?

1.5-3.5 x 10^9/L Signup and view all the answers

Which cell surface proteins are crucial for presenting bits of cell contents for immune identification?

Major Histocompatibility Complex (MHC) Signup and view all the answers

In humans, which HLA group is not associated with MHC-I?

HLA-DR Signup and view all the answers

What is the role of MHC-I when a cell is infected?

To present intracellular material to the outside Signup and view all the answers

How do T lymphocytes contribute to immunity?

By directly attacking pathogens Signup and view all the answers

What percentage of lymphocytes in the blood are T lymphocytes?

75% Signup and view all the answers

What is a defining characteristic of lymphocytes compared to neutrophils?

Large and relatively round nucleus Signup and view all the answers

Which type of immunity do Natural Killer (NK) cells belong to?

Innate immunity Signup and view all the answers

What is the primary role of B-lymphocytes in the immune response?

To mount a specific immune response by producing antigen-specific antibodies Signup and view all the answers

What two signals are required for the activation of T-cells?

Recognition of peptide:MHC complexes and co-stimulation Signup and view all the answers

In what locations do T-cells undergo positive and negative selection?

Thymus cortex and cortex-medulla border Signup and view all the answers

What secretory characteristic is notable in plasma cells?

Extensive Rough Endoplasmic Reticulum and Golgi apparatus Signup and view all the answers

What does central tolerance test B-cells for before they leave the bone marrow?

Reaction to self proteins Signup and view all the answers

What type of MHC molecules do B cells express?

MHC-II molecules Signup and view all the answers

What is the consequence of the random generation of B cell receptors?

Increased likelihood of autoimmune diseases Signup and view all the answers

What indicates a longer period since infection when examining antibodies in blood?

Presence of only IgG antibodies Signup and view all the answers

What is the apoptotic mechanism's role in B cell development?

To eliminate B cells that react strongly to self proteins Signup and view all the answers

How many molecules of a single antibody does a B cell typically have on its surface?

About 150,000 molecules Signup and view all the answers

Study Notes

Innate Immune Cells

Macrophages and granulocytes are key innate immune cells.
Neutrophils, eosinophils, basophils, mast cells, dendritic cells, and NK (Natural Killer) cells are also included in this category.
Innate immune response features: fast, non-specific, and generic.

Function of Innate Immune Cells

Phagocytosis: Involves macrophages, neutrophils, and eosinophils to engulf and digest pathogens.
Immunological Surveillance: NK cells monitor for abnormal cells.
Physical Barriers: Skin, epithelial membranes, hair, and one-way urine flow act as initial defenses.
Natural Antimicrobial Substances: Include HCl, lysozyme, natural antibodies, saliva, interferons, and complement proteins.

Inflammation

Four classic signs of inflammation: rubor (redness), calor (heat), dolor (pain), tumor (swelling).

Adaptive Immune Cells

Adaptive immune response depends on highly specialized cells: T lymphocytes and B lymphocytes.
B lymphocytes are responsible for humoral immunity by producing antigen-specific antibodies, while T lymphocytes facilitate cell-mediated immunity.

Specificity of Adaptive Immunity

Unique to specific antigens and establishes immunological memory for faster responses upon re-exposure.
Lymphocytes possess large, round nuclei and are slightly smaller than neutrophils.

Lymphocyte Characteristics

Normal lymphocyte count: 1.5-3.5 x 10^9/L.
Lifespan of lymphocytes can extend for many years.
Lymphocytes are divided into T-cells and B-cells, with T-cells comprising about 75% of circulating lymphocytes.

Role of Major Histocompatibility Complex (MHC)

MHC molecules allow immune cells to distinguish self from non-self.
MHC-I presents intracellular material and is found on all nucleated cells.
MHC-II is present on antigen-presenting cells (APCs) like dendritic cells, macrophages, and B-cells.
Human leukocyte antigen (HLA) gene encodes MHCs, with three main groups: HLA-A, HLA-B, HLA-DR.

T Lymphocyte Function

T helper cells (CD4+) bind to MHC-II for recognition and activation.
Cytotoxic T cells (CD8+) bind to MHC-I, recognize infected cells, and induce apoptosis through perforin and interferon-gamma (IFN-γ).

B Lymphocyte Function

B lymphocytes (produced in bone marrow) mount specific immune responses by secreting antibodies.
Antibodies neutralize toxins, opsonize pathogens for phagocytosis, and activate the complement system.
Memory B cells confer long-term immunity and produce high-affinity antibodies upon re-exposure.

Development of T-cells

Thymocytes undergo positive selection (functional receptor) in the cortex and negative selection (removing self-reactive cells) at the cortex-medulla border.
About 95-98% of thymocytes undergo apoptosis before reaching maturity.

Antibody Production and Action

Plasma cells secrete up to 2000 antibodies per second and produce various antibody types, including IgM and IgG.
Antibody functions include:
- Opsonization: Enhances phagocytosis.
- Complement Activation: Leads to lysis and enhances phagocytosis.
- Neutralization: Prevents the action of toxins and pathogens.

True/False Statements

B-cells have CD19 on their surface - true.
Plasma cells can secrete up to 200 antibodies per cell per second - false, it’s 2000.
Antibodies defend the body through complement activation, opsonization, and neutralization - true.

Summary of Immune Response Types

Cell-mediated response (T-cells): Protects against intracellular organisms.
Humoral response (B-cells): Plasma cells release antibodies to defend against extracellular threats.

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Description

Test your knowledge on the innate and adaptive immune cells, including the roles of various white blood cells (WBCs) like macrophages, neutrophils, and lymphocytes. This quiz covers the main features and functions of the immune system, helping you understand the crucial elements of defense and immunity.