Immunology Quiz: Antibodies and B Cells

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Questions and Answers

What is the name of the process whereby the antibody produced by B cells changes from IgM to IgG?

Isotype switching (correct)

Affinity maturation

Somatic mutation

Clonal expansion

What happens to a B cell after it encounters an antigen for the first time and is not activated by a T cell?

The B cell is silenced. (correct)

The B cell undergoes clonal expansion.

The B cell releases IgM pentamer into the plasma.

The B cell continues to circulate as a mature naive B cell.

Which of the following is NOT a function of IgG antibodies?

Represent the second wave of immune response

Coat microbes for phagocytosis

Secreted in mucosal tissue (correct)

Actively transported across the placenta

What type of T cell is responsible for stimulating B cell proliferation?

Helper T cells (CD4+) (A) Signup and view all the answers

Which of the following statements about blood typing is TRUE?

Blood type is determined by the presence of specific antigens on red blood cells. (B) Signup and view all the answers

What are the main functions of antibodies produced by B cells?

To bind to specific foreign molecules and inactivate them. (B) Signup and view all the answers

What is the role of 'memory cells' in the immune response?

They are responsible for the second wave of immune response. (C) Signup and view all the answers

Which type of antibody is primarily responsible for the initial response to an antigen?

IgM (D) Signup and view all the answers

What is the key difference between mature naive B cells and memory B cells?

Mature naive B cells have IgM on their cell surface, while memory B cells have IgG on their cell surface. (C) Signup and view all the answers

Hemolytic disease of the newborn (HDN) occurs when:

The mother is Rh- and the fetus is Rh+. (D) Signup and view all the answers

What initiates the rejection of solid organ transplants?

Host T cells recognizing foreign HLA antigens (B) Signup and view all the answers

Which type of transplant rejection is characterized by rapid graft failure due to preformed antibodies?

Hyperacute rejection (A) Signup and view all the answers

Which mechanism is involved in chronic transplant rejection?

Arteriosclerosis due to T cell activation (C) Signup and view all the answers

What is the definitive method for diagnosing amyloidosis?

Biopsy demonstrating amyloid in tissue (C) Signup and view all the answers

What type of amyloidosis is usually caused by clonal proliferations of plasma cells?

Primary amyloidosis (AL type) (B) Signup and view all the answers

What is a common complication associated with transplantation of hematopoietic stem cells (HSCs)?

Graft vs. host disease (GVHD) (D) Signup and view all the answers

Which of the following statements about amyloid structures is true?

Amyloid consists of proteins that aggregate in beta-pleated sheets (B) Signup and view all the answers

What type of amyloidosis occurs secondary to an associated inflammatory condition?

Reactive systemic amyloidosis (AA type) (B) Signup and view all the answers

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

To neutralize pathogens and facilitate their removal (A) Signup and view all the answers

Which immunoglobulin is known to be the first released during an immune response?

IgM (C) Signup and view all the answers

How does somatic recombination contribute to B cell maturation?

It generates diverse immunoglobulin receptors. (D) Signup and view all the answers

What does the 'idiotype' of an antibody refer to?

The antigen-binding portion of the antibody (C) Signup and view all the answers

What happens to a B cell that does not pass the self-tolerance test?

It is eliminated or undergoes apoptosis. (D) Signup and view all the answers

Which immunoglobulin is primarily associated with mucosal immunity?

IgA (A) Signup and view all the answers

What role does the Fc portion of an immunoglobulin serve?

Interacting with immune cells and complement (B) Signup and view all the answers

Which type of immunoglobulin primarily activates mast cells?

IgE (C) Signup and view all the answers

What is the role of PRR in innate immunity?

PRR recognizes pathogen-associated molecular patterns (PAMPs) and initiates phagocytosis. (D) Signup and view all the answers

What is the role of complement protein C3b in phagocytosis?

C3b coats pathogens, making them more susceptible to phagocytosis by phagocytes. (D) Signup and view all the answers

How does phagocytosis contribute to the activation of the adaptive immune response?

Phagocytes present antigens from digested pathogens on their surface, allowing B and T cells to recognize and respond to the specific pathogen. (A) Signup and view all the answers

Which of the following are examples of PAMPs?

Lipopolysaccharides (LPS) on bacterial surfaces, flagellin from bacterial flagella, and double-stranded RNA from viruses (B) Signup and view all the answers

What is the main difference between PRR and PAMP?

PRR is a receptor on phagocytes that binds to PAMPs, which are specific markers on pathogens (D) Signup and view all the answers

Which statement accurately describes the role of neutrophils in innate immunity?

They act as phagocytes that engulf and destroy pathogens. (D) Signup and view all the answers

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

To induce vasodilation and inflammation. (A) Signup and view all the answers

Which of the following best describes the major histocompatibility complex (MHC)?

A group of proteins involved in antigen presentation. (D) Signup and view all the answers

How does the complement system contribute to innate immunity?

By recruiting leukocytes to sites of infection. (A) Signup and view all the answers

What distinguishes adaptive immunity from innate immunity?

Adaptive immunity requires initial exposure to an antigen. (A) Signup and view all the answers

Which type of cells serve as antigen-presenting cells (APCs) in the immune system?

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

Which of the following statements about immunoglobulins is correct?

They can bind to antigens to facilitate their clearance. (D) Signup and view all the answers

What is the role of macrophages in the immune system?

To engulf pathogens and present antigens to T cells. (C) Signup and view all the answers

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

To produce antibodies and control humoral immunity (A) Signup and view all the answers

Which type of T cell is responsible for recognizing 'self antigens' and determining cell survival?

CD8 T cells (A) Signup and view all the answers

What mechanism allows CD8 T cells to induce cell death?

Perforins and Fas ligand (A) Signup and view all the answers

What defines the role of CD4 T cells in the adaptive immune response?

They activate B cells and enhance immune responses. (A) Signup and view all the answers

Where do T cells mature after leaving the bone marrow?

Thymus (D) Signup and view all the answers

Which MHC class is associated with presenting antigens to CD8 T cells?

MHC I (D) Signup and view all the answers

What characteristic of the adaptive immune system contributes to its effectiveness against previously encountered pathogens?

Memory component of immune cells (C) Signup and view all the answers

What is the consequence of a lack of the 'self antigen' being presented on a cell's surface?

The CD8 T cell will destroy the cell. (D) Signup and view all the answers

What function do phagocytic antigen-presenting cells (APCs) serve in the immune response?

Present foreign antigens to CD4 T cells (C) Signup and view all the answers

What is true about the genes coding for Major Histocompatibility Complex (MHC) in humans?

They are polymorphic and found on chromosome 6. (A) Signup and view all the answers

Study Notes

Objectives

Compare and contrast natural and acquired immunity
List main organs, cells, and proteins involved in the immune response
Understand the structure of immunoglobulins and their reaction with antigens
Explain the role of MHC in antigen presentation
Describe the genetic basis of ABO and Rh blood groups
Relate HLA alleles to autoimmune disease
List the four mechanisms of hypersensitivity reactions
Explain the principle of blood transfusion
Distinguish between systemic and organ-specific autoimmune diseases
Define and describe the pathogenesis and molecular basis of SLE and rheumatoid arthritis
Describe the pathogenesis and complications of AIDS
Differentiate the three forms of amyloid and relate them to clinical presentations of amyloidosis
Debate the pathologic cause of transplant rejection

Innate vs Adaptive Immunity

Innate immunity—fast response, nonspecific, no memory
Adaptive immunity—slower response, specific, has memory

Innate Immune Cell Types

Neutrophils - phagocytes with granules containing enzymes
Macrophages - phagocytes, antigen-presenting cells (APCs)
Dendritic Cells - phagocytes, APCs
NK cells - phagocytes

Innate Immune Complement

Chemotaxis - recruitment of leukocytes
Opsonization - marking a target on a microbe
MAC - attack complex forming a pore

Innate Immune Cytokines

Induce inflammation
Induce vasodilation
Cause fever
Damage microbes

Innate Immune PRR + PAMP Phagocytosis

Phagocytes have pattern recognition receptors (PRRs) to recognize pathogen-associated molecular patterns (PAMPs)
PAMPs are essential to pathogens' life cycles
PRR + PAMP initiates phagocytosis and cytokine release

Innate Immune Antigen Presentation

The adaptive immune system is introduced to foreign invaders
The pathogen is digested inside the phagosome
Bits of the pathogen are placed on the APC surface
APC encounters B and T cells
This starts a further phagocytic response

Phagocytosis and Adaptive Involvement

3 ways to grab a pathogen:
- PRR + PAMP
- C3b receptor + complement
- Antibody + FC receptor

Adaptive Immune System Traits

Generates specific chemical and cellular responses to destroy pathogens
More effective than nonspecific defenses
Has a memory component
Mediated by lymphocytes

Adaptive Immune Cell Types

B cells: mature in bone marrow, produce antibodies. Controls antibody-mediated (humoral) immunity
T cells: mature in thymus. Develop from naive →effector cells with the help of antigen-presenting cells to develop cytotoxic T cells & cell-mediated (cellular) immunity

T Cells: MHC

MHC I: expressed on all cells, T cells patrol for foreign antigens, destroys cells with missing or incorrect antigens
MHC II: on antigen presenting cells, helper T cells activate B cells to proliferate (and B cells recognize the foreign antigens)

T-Cell Weapons

Perforins - poke holes in membranes
Fas ligand - activates apoptosis
Cytokines activate apoptosis

T cells: MHC Type II

This protein is on phagocytic APCs - a bit of the ingested pathogen is presented
Helper T cells (CD4) recognize it and activate B cells to proliferate

Receptors

Innate PAMP
T cells: MHC I, MHC II

HLA

Gene complex coding MHC in human cells
Located on chromosome 6
HLA genes are polymorphic
Inheritance of particular HLA alleles can form harmful immune responses

Transition

The presentation of adaptive immunity to the immune response
How adaptive immunity evolved
Explanation of adaptive immunity's key machinery

Immunoglobulins

Y-shaped proteins that can be either an antibody or a receptor
Fab portion - antigen binding tips
Fc portion - stem
Variable portion
Hypervariable region

B cell Antibody Isotypes

IgM: released as a pentamer
IgD: cell doesn´t work
IgG: monomer, strong
IgA: mucosa
IgE: mast cells

B cell Maturation & Activation

B cells start in the bone marrow
B cells have 10^12 number of cells making receptors for every possible antigen through somatic recombination.
B cells are tested for self-tolerance
B cells are activated during the second wave if the pathogen is found to be “correctly” defined

B cell Specialization

Mature naïve B cell reacts to an antigen:
Releases IgM pentameter into plasma
IgM is fast and not specific
Activated plasma cell releases IgM as a pentameter
Memory B cells have IgG on cell surface, IgG releases as a monomer.

T and B cell recap

Helper T cells (CD4+): stimulates proliferation of B cells and also stimulate phagocytes
Cytotoxic T cells (CD8+): destroy infected cells, directly attack viruses, bacteria, cancer, & transplanted organs
Memory T cells: activate immune response if same antigen is reintroduced
B cells are genetically programmed to produce antibodies (plasma cells)
Antibodies: proteins produced by B cells, bind and inactivate foreign molecules (antigens)

Antibodies Recap

IgG: opsonizes microbes for phagocytosis, crosses the placenta
IgM & IgG: first & second waves of immune response
IgA: secretions in mucosal tissues
IgE: asthma & allergies, coats helminthic parasites, works with mast cells & eosinophils to kill them.

Blood Typing

Two primary blood groups - ABO and Rh
Important to note antigens are not present, body produces antibodies
Self-tolerance not developed so antibodies can be made

Rh Factor and Pregnancy

Mother-fetus incompatibility in the Rh system can result in the destruction of fetal red blood cells
Hemolytic disease of the newborn (HDN) - occurs when mothers are Rh- and fetus is Rh+, causing maternal antibodies to destroy the fetus's blood cells
Rh antibodies attack Rh+ fetuses.

Hypersensitivity

Type I: immediate hypersensitivity, allergies
Type II: cytotoxic reaction, antibodies attack self cells
Type III: immune complex deposition, small vessels
Type IV: cell-mediated, T cells attack

Autoimmune Diseases

The immune system attacks self-antigens & kills cells and tissues of the body
Examples of systemic diseases: systemic lupus erythematosus, rheumatic fever, rheumatoid arthritis, & systemic sclerosis
Examples of System/organ-Specific diseases: Multiple sclerosis, Hashimoto Thyroiditis, Autoimmune hemolytic anemia, Membranoproliferative glomerulonephritis, Primary biliary cirrhosis, Pemphigus vulgaris, & Myasthenia gravis

Rheumatoid Arthritis

Chronic, systemic inflammatory, autoimmune disease affecting joints
Also affects synovial membranes
Prevalence of 1% (3-5X more common in women)
Any age, usually in second to fourth decades
Genetic predisposition
Environmental trigger activates helper T cells
Type IV hypersensitivity

Systemic Lupus Erythematosus

Systemic autoimmune disease
Caused by autoantibodies & the formation of immune complexes
Fatigue, fever, malaise, nephritis, skin lesions, & arthritis
More common in females & young adults over 30
Inherited susceptibility in class II MHC and complement genes
Type III hypersensitivity

AIDS (Acquired Immunodeficiency Syndrome)

A collection of disorders due to HIV infection
HIV targets and kills helper T cells
Transmission through blood or body fluids
Sexual contact, parenteral inoculation (IV drug users, blood transfusions), vertical transmission (infected mothers to newborns)

HIV Infection & Replication

Viral RNA enters a helper T cell
Viral RNA is transcribed (reverse transcription) into viral DNA
Viral DNA integrates into host cell's DNA
DNA including viral genes is transcribed
Some transcripts form new viral RNA, others translated into proteins
Proteins assemble as new virus particles

Progression of HIV Infection

Acute phase: high levels of virus production, signs of systemic infection, seroconversion
Chronic phase (clinical latency): virus continues to replicate, immune system largely intact
Later stage: helper T cells decline, immune defenses diminish, opportunistic infections

Pathologic Findings in AIDS

Catastrophic breakdown of immune defenses, marked increase in viremia, reduced CD4+ cell count (below 200 cells/L)
Serious opportunistic infections, secondary neoplasms, neurological manifestations
Symptoms: vary from CNS to skin and the rest of the body

Misc.

Transplant rejection - initiates due to host T-cells recognizing foreign HLA antigens of a graft
Types include: hyperacute, acute cellular, acute antibody-mediated, and chronic
Treatment involves immunosuppressants for immune response
Amyloidosis - a group of conditions where extracellular deposits of fibrillar proteins cause tissue damage
Amyloid diagnosed by demonstration of amyloid in tissue requiring biopsy
Primary amyloidosis: usually AL type, clonal proliferations of plasma cells such as multiple myeloma
Reactive systemic amyloidosis: occurs secondary to inflammation, AA type

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Description

Test your knowledge on the immune system with this quiz focused on antibodies produced by B cells. Explore topics such as antibody classes, B cell activation, and the roles of memory cells. Challenge yourself with various questions related to blood typing and transplant rejection.