Lymphocytes

Questions and Answers

What is the primary role of memory B cells in the immune system?

To activate T-cells during an immune response.

To differentiate into plasma cells that secrete large amounts of antibodies.

To create immunological memory for rapid response upon re-exposure to a pathogen. (correct)

To produce antibodies immediately upon first exposure to a pathogen.

Which statement is accurate regarding the surface characteristics of B-cells?

B-cells express IgM and IgD on their surface.

B-cells can only be found in the blood.

B-cells have CD19 on their surface. (correct)

B-cells do not have any surface markers.

How many antibodies can a plasma cell secrete per second?

200 Ab/cell/second

20 Ab/cell/second

2000 Ab/cell/second (correct)

20000 Ab/cell/second

Which of the following correctly describes MHC molecules?

MHC-II is only found on antigen-presenting cells (APCs). Signup and view all the answers

What is one function of antibodies in the immune system?

They enhance the ability of phagocytes to engulf pathogens. Signup and view all the answers

Which of the following is NOT a type of innate immune cell?

B lymphocytes Signup and view all the answers

What is one key feature of the innate immune response?

Non-Specific Signup and view all the answers

Which cells are primarily involved in the process of phagocytosis?

Macrophages, Neutrophils, Eosinophils Signup and view all the answers

Which immune cells play a vital role in immunological surveillance?

Natural Killer cells Signup and view all the answers

What are the four classical signs of inflammation?

Redness, Heat, Pain, Swelling Signup and view all the answers

Which of the following is considered a physical barrier in immune defense?

Epithelial membranes Signup and view all the answers

Which of the following substances is part of the innate immune system's natural antimicrobial agents?

Lysozyme Signup and view all the answers

What characteristic defines the speed of the innate immune response?

Immediate Signup and view all the answers

What is the primary role of T cytotoxic (TC) lymphocytes?

To recognize and eliminate altered host-cells through killing Signup and view all the answers

What membrane glycoprotein do T cytotoxic lymphocytes express?

CD8 Signup and view all the answers

When are T cytotoxic lymphocytes activated?

When they interact with an antigen-class I MHC complex Signup and view all the answers

How do CD8+ T-cytotoxic cells induce cell death?

By apoptosis Signup and view all the answers

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

To limit viral replication Signup and view all the answers

What is the role of T helper (TH) lymphocytes?

To enhance the function of other immune cells Signup and view all the answers

What type of MHC molecules do TH lymphocytes recognize?

MHC-II Signup and view all the answers

What co-receptor is expressed by B cells?

CD19 Signup and view all the answers

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

Development of autoimmune responses Signup and view all the answers

What is the production rate of antibodies by plasma cells?

2000 antibodies per cell per second Signup and view all the answers

What indicates a recent infection when testing blood antibodies?

Presence of both IgM and IgG Signup and view all the answers

What process tests B cells for reaction to self proteins before they mature?

Central tolerance Signup and view all the answers

What type of antibodies do B lymphocytes primarily produce during the initial response?

IgM Signup and view all the answers

What happens to B cells that strongly react to self proteins?

They are eliminated by apoptosis Signup and view all the answers

What is the primary function of T lymphocytes in the immune system?

Killing infected cells Signup and view all the answers

Which of the following describes the ability of antigen-specific immunity after initial exposure?

It provides improved defense upon re-exposure Signup and view all the answers

What is the normal range of lymphocytes in the blood per liter?

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

What type of immunity do B lymphocytes primarily mediate?

Humoral immunity Signup and view all the answers

Which surface proteins are responsible for presenting bits of the cell's contents to the immune system?

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

What is the life span of lymphocytes?

Many years Signup and view all the answers

What percentage of lymphocytes in the blood are T lymphocytes?

75% Signup and view all the answers

Which type of lymphocyte is known for producing antigen-specific antibodies?

B lymphocytes Signup and view all the answers

What does 'CD' signify in the context of lymphocytes?

Cluster Differentiation markers Signup and view all the answers

What occurs in the thymus during the maturation of thymocytes?

Both positive and negative selection 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 the thymus in the immune system?

To generate and select T-cells Signup and view all the answers

What molecules do CD8+ T cytotoxic cells recognize?

MHC-I Signup and view all the answers

What characterizes Large Granular Lymphocytes (LGL)?

They include Natural Killer cells Signup and view all the answers

Which statement accurately describes memory B cells?

They confer rapid secondary responses and can produce IgA, IgG, and IgE. Signup and view all the answers

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

They release antibodies into the plasma for immune defense. Signup and view all the answers

Which of the following is true regarding the CD markers on T-helper and T-cytotoxic cells?

MHC-II molecules are recognized by CD4+ T-helper cells. Signup and view all the answers

Which of the following distinguishes MHC-I from MHC-II molecules?

MHC-I is found on all nucleated cells, while MHC-II is restricted to APCs. Signup and view all the answers

What is the primary role of antibodies in the immune response?

They prevent pathogen entry by neutralization and opsonization. Signup and view all the answers

What is the primary function of Major Histocompatibility Complex (MHC) molecules in the immune system?

Presenting cell contents to identify self or non-self Signup and view all the answers

Which statement about T lymphocytes is NOT true?

CD8+ T cytotoxic cells recognize MHC-II. Signup and view all the answers

How many main HLA groups are inherited as a set in humans?

Three Signup and view all the answers

Which of the following innate immune cells is specifically involved in phagocytosis?

Neutrophils Signup and view all the answers

What is the role of thymocytes in the thymus?

They undergo positive and negative selection. Signup and view all the answers

What distinguishes the populations of lymphocytes?

Presence of different membrane proteins (CD molecules) Signup and view all the answers

What feature differentiates the innate immune response from the adaptive immune response?

It is fast and generic. Signup and view all the answers

Which statement accurately describes the role of Natural Killer (NK) cells?

They conduct immunological surveillance. Signup and view all the answers

What is the main cellular difference between B lymphocytes and T lymphocytes?

B lymphocytes produce antibodies, while T lymphocytes do not. Signup and view all the answers

What percentage of thymocytes die by apoptosis before reaching maturity?

95-98% Signup and view all the answers

Identify the physical barriers that contribute to the innate immune defense.

Skin and epithelial membranes Signup and view all the answers

What are the classical signs of inflammation that indicate a response to injury or infection?

Redness, heat, pain, swelling Signup and view all the answers

Which type of T cells are primarily responsible for recognizing and acting on MHC-I molecules?

CD8+ T cytotoxic cells Signup and view all the answers

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

Immunoglobulins Signup and view all the answers

What characterizes the immune response associated with antigen-specific immunity after an initial exposure?

It results in immunological memory for faster future responses. Signup and view all the answers

Which cells can be classified as antigen-presenting cells (APCs)?

B lymphocytes, dendritic cells, and macrophages Signup and view all the answers

Which characteristic of the innate immune response contributes to its non-specific nature?

Immediate response to any pathogen Signup and view all the answers

In which part of the thymus do thymocytes undergo negative selection?

Cortex-medulla border Signup and view all the answers

What type of immunity relies primarily on the recognition of specific antigens?

Adaptive immunity Signup and view all the answers

What is the primary differentiating feature of Natural Killer (NK) cells?

They directly kill infected cells and tumors. Signup and view all the answers

What does 'TH' denote in the lymphocyte classification system?

T-helper lymphocytes Signup and view all the answers

What type of material do HLA molecules present to cell surfaces?

Intracellular material Signup and view all the answers

Which cell type executes the process of positive selection in the thymus?

Thymocytes Signup and view all the answers

What is the primary mechanism by which CD8+ T-cytotoxic cells induce cell death in infected or altered host cells?

By facilitating cell lysis via pore formation Signup and view all the answers

What is the consequence when a B lymphocyte binds to an antigen without proper co-stimulation?

Anergic state and failure to respond Signup and view all the answers

Which of the following best describes the role of CD4+ T-helper cells in the immune response?

Assist other immune cells with activation Signup and view all the answers

What characterizes the antibody production sequence in response to an infection?

Initial production is IgM, followed by IgG after class switching Signup and view all the answers

What selective process ensures that B cell progenitors do not react strongly to self-proteins?

Central tolerance Signup and view all the answers

What is the primary function of the perforin protein secreted by CD8+ T-cytotoxic cells?

To create channels in target cell membranes Signup and view all the answers

Which surface marker do T helper lymphocytes utilize for their interaction with MHC molecules?

CD4 Signup and view all the answers

What distinguishes the most recent exposure in the context of antibody testing?

Presence of both IgM and IgG antibodies Signup and view all the answers

How do B lymphocytes primarily recognize specific antigens?

Via surface antibodies specific to the antigen Signup and view all the answers

What mechanism do B cells undergo to eliminate those that strongly react to self proteins?

Apoptosis Signup and view all the answers

What co-receptor provides assistance to T cells during activation through interaction with MHC molecules?

CD28 Signup and view all the answers

What describes the function of IFN-γ in the immune response?

It inhibits viral replication and limits infection spread Signup and view all the answers

What negative outcome might occur if B cells fail during central tolerance?

Development of autoimmune conditions Signup and view all the answers

Match the following innate immune cells with their primary function:

Macrophages = Engulf and digest pathogens via phagocytosis Neutrophils = First responders to infection Eosinophils = Defense against parasites Mast Cells = Release histamines to initiate inflammation Signup and view all the answers

Match the following signs of inflammation with their Latin terms:

Redness = Rubor Heat = Calor Pain = Dolor Swelling = Tumor Signup and view all the answers

Match the following natural antimicrobial substances with their description:

HCl = Stomach acid that helps kill pathogens Lysozyme = Enzyme that breaks down bacterial cell walls Interferons = Proteins that inhibit viral replication Complement = Protein system that enhances immune responses Signup and view all the answers

Match the following immune responses with their characteristics:

Innate immunity = Fast and non-specific Adaptive immunity = Specific to particular antigens Phagocytosis = Process of engulfing pathogens Immunological surveillance = Constant monitoring for abnormal cells Signup and view all the answers

Match the following innate immune cells with their primary roles:

Natural Killer Cells = Immunological surveillance and killing infected cells Dendritic Cells = Antigen presentation and activation of T cells Granulocytes = Release substances that trap or kill pathogens Mast Cells = Participate in allergic responses and inflammation Signup and view all the answers

Match the following types of innate immune responses with their descriptions:

Phagocytosis = Engulfing and digesting of pathogens Inflammatory response = Body's response to injury or infection Natural barriers = Physical obstacles against infection Antimicrobial substances = Chemical agents that destroy microbes Signup and view all the answers

Match the following types of immune cells with their specific roles:

Neutrophils = Rapid response to bacterial infection Eosinophils = Attack multicellular parasites and modulate allergic inflammation Basophils = Release histamine during allergic reactions NK Cells = Destroy virus-infected and cancerous cells Signup and view all the answers

Match the following features of the immune responses with their types:

Fast response = Innate immunity Specific targeting = Adaptive immunity Non-specific defense mechanisms = Innate immunity Memory formation after exposure = Adaptive immunity Signup and view all the answers

Match each type of cell with its correct description:

Memory B Cells = Confer immunological memory and can rapidly respond to pathogens Plasma Cells = Specialized B-cells that secrete antibodies T-helper Cells = CD4+ cells that bind MHC-II Cytotoxic T Cells = CD8+ cells that destroy infected cells Signup and view all the answers

Match the surface markers with the corresponding cell type:

CD19 = B-cells CD4 = T-helper cells CD8 = Cytotoxic T cells MHC-I = Nucleated cells Signup and view all the answers

Match the immune response process to its correct function:

Humoral response = Production of antibodies by plasma cells Cell-mediated response = Protection against intracellular pathogens Antibody opsonization = Enhancement of phagocytosis Complement activation = Lysis of pathogens and recruitment of immune cells Signup and view all the answers

Match the statement about immune system functions with its correct truth value:

B-cells have CD19 on their surface = True Plasma cells secrete 200 antibodies per second = False MHC-II molecules are found on APCs = True Antibodies are produced only during the initial immune response = False Signup and view all the answers

Match the antibody classes to their primary function:

IgA = Mucosal immunity IgG = Long-term antibody response IgE = Allergic reactions and parasite defense IgM = Initial response to an antigen Signup and view all the answers

Match the type of T lymphocytes with their functions:

CD4+ T-helper cells = Recognize MHC-II and assist in immune responses CD8+ T cytotoxic cells = Recognize MHC-I and kill infected cells Thymocytes = Immature T-cells maturing in the thymus Natural Killer (NK) cells = Part of innate immunity and attack infected or tumor cells Signup and view all the answers

Match the cell surface proteins with their corresponding types of MHC:

MHC-I = Found on all nucleated cells MHC-II = Found on antigen-presenting cells Major Histocompatibility Complex (MHC) = Responsible for presenting cell contents Human Leukocyte Antigen (HLA) = Gene encoding MHCs in humans Signup and view all the answers

Match the immunity type with its characteristics:

Humoral immunity = Mediated by antibodies produced by B cells Cell-mediated immunity = Involves T lymphocytes killing infected cells Innate immunity = Provides a rapid response to infections Adaptive immunity = Involves memory for faster responses to re-exposure Signup and view all the answers

Match the stage of thymocyte development with its process:

Positive selection = Thymocytes with functional receptors survive Negative selection = Elimination of cells that recognize self Differentiation = Thymocytes develop into CD4+ or CD8+ T-lymphocytes Maturation = Thymocytes progress through thymic cortex and medulla Signup and view all the answers

Match the type of B lymphocyte with its role:

Plasma cells = Secrete antibodies Memory B cells = Facilitate rapid response upon re-exposure B lymphocytes = Produce antigen-specific antibodies Antigen-presenting cells (APC) = Present antigens to T cells Signup and view all the answers

Match the health relevance of HLA with its description:

HLA compatibility = Determines suitability for organ transplants HLA alleles = Varies among individuals; contributes to immune diversity HLA inheritance = Each person inherits different sets from each parent HLA testing = Used to match donors with transplant recipients Signup and view all the answers

Match the lymphocyte type with the percentage in circulation:

B lymphocytes = Approximately 20% of lymphocytes T lymphocytes = Approximately 75% of lymphocytes Natural Killer (NK) cells = A minor percentage compared to T and B cells CD4+ T-helper cells = About 40% of T lymphocytes Signup and view all the answers

Match the identification process with its components:

Self vs. Non-self recognition = Cells present bits of their contents MHC molecules = Role in identifying self/non-self Antigen presentation = Involves T cell activation Cellular immune response = Lymphocytes target infected cells Signup and view all the answers

Match the lifespan of lymphocytes with its characteristics:

B lymphocytes = Generally short-lived but can form memory cells T lymphocytes = Can persist for many years Thymocytes = Get eliminated during development Plasma cells = Secrete antibodies temporarily before dying Signup and view all the answers

Match the features of MHC molecules with their corresponding characteristics:

MHC-I molecules = Present intracellular antigens MHC-II molecules = Present extracellular antigens MHC restriction = Requires specific T cell types to function Antigen presentation = Enables T cells to identify threats Signup and view all the answers

Match the types of immunity with their associated cell types:

Innate immunity = Natural Killer (NK) cells Adaptive immunity = B lymphocytes and T lymphocytes Humoral immunity = Involves B cells producing antibodies Cell-mediated immunity = Involves T cells attacking infected cells Signup and view all the answers

Match the features of T lymphocytes with their functions:

TC lymphocytes = Cytotoxic activity TH lymphocytes = Help activate B cells and other immune cells Memory T cells = Prompt faster responses upon re-exposure Regulatory T cells = Control immune responses to prevent overactivity Signup and view all the answers

Match the following cell types with their immunological role:

Dendritic cells = Antigen-presenting cells for T lymphocytes Macrophages = Phagocytose pathogens and present antigens Helper T cells = Assist in activating immune responses Cytotoxic T cells = Directly kill infected host cells Signup and view all the answers

Match the T cell classification with its markers:

CD4+ T-helper cells = Recognize MHC-II CD8+ T cytotoxic cells = Recognize MHC-I Memory T cells = Long-lived, increased population upon re-exposure Regulatory T cells = Express CD25 and help moderate the immune response Signup and view all the answers

Match the following processes with the corresponding definitions:

Apoptosis in thymocytes = Elimination of self-reactive cells Differentiation of thymocytes = Development into functional T lymphocytes Positive selection in the thymus = Survival of cells with functional TCR Negative selection in the thymus = Death of thymocytes recognizing self-antigens Signup and view all the answers

Match the immune cell type with its characteristic membrane glycoprotein:

T cytotoxic lymphocytes = CD8 T helper lymphocytes = CD4 B lymphocytes = CD19 Plasma cells = CD40 Signup and view all the answers

Match the type of MHC molecules with the lymphocyte that recognizes them:

T cytotoxic lymphocytes = Class I MHC molecules T helper lymphocytes = Class II MHC molecules B lymphocytes = Class II MHC molecules Natural Killer cells = Class I MHC molecules Signup and view all the answers

Match the antibody action with its description:

Opsonization = Enhances phagocytosis by coating antigens Complement Activation = Causes lysis through the complement system Neutralization = Prevents toxins or pathogens from acting Agglutination = Clumping of pathogens for easier elimination Signup and view all the answers

Match the function of interferon-gamma (IFN-γ) with its role:

Limits viral replication = Inhibits the synthesis of viral proteins Enhances antigen presentation = Increases expression of MHC molecules Stimulates macrophage activity = Promotes phagocytosis of pathogens Increases T cell activation = Enhances proliferation of T lymphocytes Signup and view all the answers

Match the feature with the corresponding immune cell:

CD8+ T lymphocytes = Kill altered host cells CD4+ T helper cells = Help activate other immune cells B lymphocytes = Produce antibodies Plasma cells = Secrete antibodies at high rates Signup and view all the answers

Match the process with its associated immune cell activity:

Central tolerance = Elimination of self-reactive B cells Activation of CD8+ T cells = Recognition of antigen-Class I MHC complex Activation of CD4+ T cells = Recognition of antigen-Class II MHC complex Antibody class switching = Change from IgM to IgG production Signup and view all the answers

Match each cytokine or secreted molecule with its function:

Interferon-gamma = Limits viral spread IL-2 = Stimulates T cell growth Tumor necrosis factor-alpha = Induces inflammation Chemokines = Attract immune cells to sites of infection Signup and view all the answers

Match the statement about B lymphocytes with its fact:

B lymphocytes production site = Bone marrow B lymphocytes circulation = Blood, spleen, lymph nodes B cell receptor type = Surface antibody (IgD/IgM/IgG) Major MHC type on B cells = Class II MHC molecules Signup and view all the answers

Match each feature of antibodies with its description:

IgM = First antibody produced during the immune response IgG = Most abundant antibody in serum IgD = B cell receptor for antigen recognition IgA = Found in mucosal areas and secretions Signup and view all the answers

Match the immune challenge with the antibody response indicator:

Recent infection = Presence of both IgM and IgG Long-term infection = Presence of only IgG No immune response = Absence of antibodies Primary immune response = Predominantly IgM production Signup and view all the answers

Match the method of apoptosis in T cytotoxic cells with its mechanism:

Perforin = Creates pores in target cell membranes Granzyme = Induces apoptosis from within the target cell Fas ligand = Engages death receptor on target cell Caspase cascades = Executors of the apoptosis process Signup and view all the answers

Match the condition with its outcome regarding immune cells:

Self-reactive B cells = Eliminated by central tolerance Activated CD8+ T cells = Kill infected cells Activated CD4+ T cells = Support other immune responses Memory B cells = Provide long-term immunity Signup and view all the answers

Match each immune cell type with their primary function:

B lymphocytes = Produce antibodies T cytotoxic lymphocytes = Kill infected or malignant cells T helper lymphocytes = Regulate immune responses Natural Killer cells = Provide innate defense against tumors and virally infected cells Signup and view all the answers

Match each function of antibodies with their respective roles:

Opsonization = Facilitates phagocytosis Complement activation = Enhances lysis of pathogens Neutralization = Inhibits pathogen function Antibody-dependent cellular cytotoxicity = Engages immune cells to kill targets Signup and view all the answers

Match the lymphocyte type with its unique activation triggers:

CD8+ T cells = Interaction with Class I MHC CD4+ T cells = Interaction with Class II MHC B cells = Binding of specific antigens to B cell receptors Natural Killer cells = Recognition of stressed cells in the absence of MHC Signup and view all the answers

Study Notes

Innate Immune Cells

Include macrophages, granulocytes, neutrophils, eosinophils, basophils, mast cells, dendritic cells, and natural killer (NK) cells.
Main features: fast, non-specific, and generic immune response.
Innate immune cells involved in phagocytosis: macrophages, neutrophils, and eosinophils.

Adaptive Immune Cells

Composed of highly specialized cells like B lymphocytes and T lymphocytes.
B lymphocytes are responsible for humoral immunity through antibody production.
T lymphocytes carry out cell-mediated immunity, targeting infected cells.

Phagocytosis and Immunological Defense

Process by which macrophages, neutrophils, and eosinophils engulf and digest pathogens.
Natural killer cells perform immunological surveillance, detecting virus-infected cells.
Physical barriers include skin, epithelial membranes, hair, and one-way urine flow.

Antimicrobial Substances

Natural substances that provide defense include HCl, lysozyme, natural antibodies, saliva, interferons, and complement proteins.

Inflammation

Characterized by rubor (redness), calor (heat), dolor (pain), and tumor (swelling).

Antigen-Specific Immunity

Unique to specific antigens and involves a time lag to maximum response.
Offers immunological memory for faster responses upon re-exposure.

Lymphocyte Characteristics

Normal range: 1.5-3.5 x 10^9/L in blood; can persist for many years.
Central role in protecting against infections; slightly smaller than neutrophils.
Large and round nuclei characteristic of lymphocytes; heterogeneous based on lineage and CD molecules expression.

Major Histocompatibility Complex (MHC)

Cell surface proteins that present intracellular material to differentiate self from non-self.
Found in all vertebrates; in humans, encoded by Human Leukocyte Antigen (HLA) genes.
MHC-I is present on all nucleated cells; MHC-II is on antigen-presenting cells (APCs).

T Lymphocytes Development

Produced and mature in the thymus, where they undergo positive and negative selection.
CD4+ T helper cells and CD8+ cytotoxic T cells recognize MHC-II and MHC-I, respectively.

Functions of T Helper and Cytotoxic Cells

TH lymphocytes aid in activating other immune cells by recognizing MHC-II.
TC lymphocytes eliminate infected cells by recognizing MHC-I and inducing apoptosis.

B Lymphocytes Development and Function

Produced and mature in the bone marrow, circulating in blood, spleen, and lymph nodes.
Recognize antigens via surface antibodies (B cell receptors) and secrete antigen-specific antibodies.

Plasma Cells and Antibody Production

Plasma cells can secrete up to 2000 antibodies per cell per second for a limited time.
Initial antibody production is IgM, followed by IgG after class switching.

Memory B Cells

Confer immunological memory for rapid responses upon subsequent infections.
Found in the spleen and lymph nodes, express high levels of IgA, IgG, and/or IgE after class switching.

Mechanisms of Antibody Action

Opsonization enhances phagocytosis; antibodies coat antigens for better recognition.
Complement activation leads to the lysis of pathogens, augmenting immune response.
Neutralization prevents toxins and pathogens from exerting harmful effects.

Summary of True/False Statements

B-cells express CD19 on their surface: true.
Plasma cells secrete 200 antibodies per cell per second: false (2000).
Antibodies defend through complement activation, opsonization, and neutralization: true.

Types of Immunity

Cell-mediated immunity involves T-cells, targeting intracellular pathogens and tumors.
Humoral immunity, primarily through plasma cells, protects against extracellular threats.

Innate Immune Cells

Innate immune cells include macrophages, granulocytes, neutrophils, eosinophils, basophils, mast cells, dendritic cells, and natural killer (NK) cells.
The innate immune response is characterized by being fast, non-specific, and generic.
Phagocytosis is performed by macrophages, neutrophils (acting as antigen-presenting cells), and eosinophils.
Immunological surveillance at body surfaces is primarily conducted by NK cells.

Physical Barriers and Natural Antimicrobials

Physical barriers such as skin, epithelial membranes, hairs, and one-way urine flow play vital roles in defense.
Natural antimicrobial substances include HCl, lysozyme, natural antibodies, saliva, interferons, and complement proteins.

Inflammation

Four classical signs of inflammation are rubor (redness), calor (heat), dolor (pain), and tumor (swelling).

Adaptive Immune Cells

Adaptive immunity involves specialized cells and is unique to specific antigens.
B lymphocytes are responsible for humoral immunity, producing antigen-specific antibodies.
T lymphocytes are involved in cell-mediated immunity, targeting infected cells.

Lymphocyte Characteristics

Lymphocytes range from 1.5 to 3.5 x 10^9/L in blood and can persist for many years.
They are classified into T cells and B cells, with T lymphocytes accounting for 75% of lymphocytes in the blood.
Lymphocytes have a large, round nucleus and are slightly smaller than neutrophils.

Major Histocompatibility Complex (MHC)

MHC molecules present intracellular material to facilitate identification of self vs. non-self.
MHC-I is found on all nucleated cells, while MHC-II is found on antigen-presenting cells (APCs).
The human equivalent of MHC is Human Leukocyte Antigen (HLA), which consists of HLA-A, HLA-B, and HLA-DR groups.
HLA group alleles include 59 for HLA-A, 118 for HLA-B, and 124 for HLA-DR.

T Lymphocyte Activation and Function

CD8+ T cells, or cytotoxic T lymphocytes, recognize MHC-I and eliminate infected cells via apoptosis.
CD4+ T cells, or T helper lymphocytes, recognize MHC-II and assist other immune cells through cytokine release.
Thymocytes undergo positive and negative selection during their maturation in the thymus; 95-98% die before reaching maturity.

B Lymphocyte Production and Function

B lymphocytes are produced and mature in bone marrow and circulate in blood, spleen, and lymph nodes.
They recognize antigens via surface antibodies (B cell receptors) and produce antigen-specific antibodies once activated.
Plasma cells, derived from B cells, secrete up to 2000 antibodies per cell per second and have extensive rough endoplasmic reticulum for secretory function.

Antibody Functions

Antibodies act through opsonization, complement activation, and neutralization of toxins.
IgM is the initial antibody produced, followed by IgG after class switching; the presence of both indicates recent infection, while only IgG indicates a longer period since infection.

Memory B Cells

Memory B cells confer immunological memory, ensuring rapid response during re-exposure to pathogens.
They primarily reside in the spleen and can produce high levels of antibodies such as IgA, IgG, and IgE after class switch.

Summary of True/False Statements

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

Immune Responses Overview

Cell-mediated response involves T-cells, targeting intracellular pathogens and cancers through specific MHC interactions.
Humoral response involves plasma cells secreting antibodies to combat extracellular bacteria and foreign macromolecules.

Innate Immune Cells

Primary innate immune cells include macrophages, granulocytes (neutrophils, eosinophils, basophils), mast cells, dendritic cells, and natural killer (NK) cells.
Macrophages and neutrophils are involved in phagocytosis, a process where cells engulf and digest pathogens.
Natural Killer cells conduct immunological surveillance, identifying and attacking infected or abnormal cells.
Physical barriers to infection include skin, epithelial membranes, hairs, and mechanisms like one-way urine flow.
Natural antimicrobial substances: HCl, lysozyme, natural antibodies, saliva, interferons, and complement proteins are critical defensive elements.

Adaptive Immune Cells

Adaptive immunity relies on highly specialized immune cells, particularly B lymphocytes (produce antibodies) and T lymphocytes (cell-mediated responses).
B lymphocytes are associated with humoral immunity while T lymphocytes focus on cell-mediated immunity.
T-helper cells (CD4+) assist other immune cells, while cytotoxic T cells (CD8+) eliminate infected cells.

Characteristics of Innate Immune Response

Features include being fast, non-specific, and generic in nature.
Inflammation displays four classical signs: rubor (redness), calor (heat), dolor (pain), and tumor (swelling).

Lymphocyte Features

Lymphocytes, slightly smaller than neutrophils, have a large, round nucleus occupying most of the cytoplasm.
Normal range of lymphocytes in blood: 1.5-3.5 x 10^9/L, with a lifespan that can extend for many years.
Lymphocytes are classified into two main types: T cells and B cells, crucial for immune response.

Role of Major Histocompatibility Complex (MHC)

MHC molecules enable the immune system to distinguish self from non-self by presenting intracellular material at the cell surface.
Found in all vertebrates, MHC genes in humans are referred to as Human Leukocyte Antigen (HLA), including HLA-A, HLA-B, and HLA-DR groups.
MHC-I is present on all nucleated cells, while MHC-II is found on antigen-presenting cells.

T Cell Maturation and Function

T cells mature in the thymus through a process of positive and negative selection, ensuring functional and self-tolerant T cell populations.
CD8+ T cytotoxic cells target MHC-I complexes, while CD4+ T helper cells recognize MHC-II complexes.
Cytotoxic T cells induce apoptosis in infected cells using perforin to create pores.

B Lymphocyte Overview

B lymphocytes produce and mature in the bone marrow, circulating through blood, spleen, and lymph nodes.
Their primary role is production of antigen-specific antibodies, which neutralize toxins and pathogens.
Memory B cells, formed post-activation, ensure rapid responses upon re-exposure to pathogens.

Antibody Functions

Antibodies perform key actions: opsonization enhances phagocytosis, complement activation leads to lysis of pathogens, and neutralization prevents pathogen action.
Plasma cells secrete high volumes of antibodies (up to 2000 per second), primarily IgM initially, followed by IgG after class switching.

Summary of Immune Responses

Cell-mediated responses protect against intracellular pathogens; humoral responses target extracellular bacteria and foreign particles.
Both types of responses involve complex interactions between various immune cells, receptors, and signaling molecules, ensuring effective immune defense.

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Description

Explore the fascinating world of innate and adaptive immune cells in this quiz. Test your knowledge on various immune cell types, their functions in phagocytosis, and the body's defense mechanisms. Dive into the specifics of B and T lymphocytes and discover how they contribute to immunity.