This image shows an antigen-presenting cell activating a CD4 Th cell. Identify (A-E), which all activate the Th cell.
(A) MHC II; (B) T-cell receptor; (C) CD4; (D) B7; (E) CD28
Shown here are two cells coactivating a third cell critical to cellular immunity. Identify the cells involved (A-C).
(A) virus-infected cell; (B) Th cell (CD4); (C) Tc cell (CD8+)
This image shows a Th cell inducing a B cell to class switch and make antibodies. Identify (A-C), which all activate the B cell.
(A) Th2 cytokines (interleukin-4, -5, and -6); (B) CD40L; (C) CD40
Identify and describe the process shown, in which the coating of a bacterium with antibodies summons an important immune cell.
Opsonization, in which an antibody promotes the phagocytosis of an antigen by a phagocyte
Identify and describe the process shown, in which the coating of a bacterium with antibodies prevents it from approaching the cells.
Neutralization, in which an antibody attaches to an antigen and prevents adherence to cells
Which cells are responsible for innate immunity?
Neutrophils, macrophages, dendritic cells, natural killer cells, and the complement system
_____ (Adaptive/Innate) immunity is encoded into the germ line and reacts to a set of static parameters that humans have adapted to combat over evolutionary time.
Innate
_____ (Adaptive/Innate) immunity has target molecules that are encoded in the germline as opposed to reacting to novel challenges.
Innate
What is the benefit of germline encoding of target antigen recognition by the innate immune system?
It allows innate immunity to be both fast and nonspecific
How does the adaptive immune response differ during first and second exposures to an antigen?
Adaptive immunity is slow to develop on first exposure but fast on any subsequent exposures
What are the components of the adaptive immune system?
T cells, B cells, and circulating antibody
Th1 and Th2 cells are specialized descendants of which type of cell?
CD4+ helper T cells
What type of T cells activate macrophages and CD8+ T cells by producing interleukin-2 and γ-interferon?
Th1 cells
What type of T cells activate B cells to make antibody by producing interleukin-4 and interleukin-5?
Th2 cells
What is the effect of interleukin-12 on T cells?
It induces the differentiation of naive helper T cells into Th1 cells, resulting in increased cell-mediated immunity
What is the role of interleukin-4 in T-cell maturation?
Interleukin-4 induces the differentiation of native helper T cells to Th2 cells resulting in increased antibody-mediated immunity
Th1 cells have what functions?
The activation of macrophages and CD8+ T cells by producing interleukin-2 and γ-interferon
Th2 cells have what functions?
The activation of B cells to make antibodies by producing interleukin-4 and interleukin-5
Where in the body are T cell precursors found?
In the bone marrow
T cell precursor cells give rise to what cell type?
CD4+/CD8+ T cells
CD4+/CD8+ T cells are found where?
In the cortex of the thymus
CD4+ T cells give rise to what cell line?
Helper T cells
CD8+ T cells give rise to what cell line?
Cytotoxic T cells
Interleukin-10 inhibits _____ (Th1/Th2) cells.
Th1 cells
What is the name of the set of genes that encode the major histocompatibility complex?
Human leukocyte antigen genes
On which cells is major histocompatibility complex I expressed?
Almost all nucleated cells
What are the three major histocompatibility complex I class genetic loci?
Human leukocyte antigen-A, human leukocyte antigen-B, and human leukocyte antigen-C
Which cells express major histocompatibility complex II?
Antigen-presenting cells
What are the three major histocompatibility complex II class genetic loci?
Human leukocyte antigen-DR, human leukocyte antigen-DP, and Human leukocyte antigen-DQ
For cells expressing major histocompatibility complex I, where is antigen loaded into the peptide-binding groove? Where does this occur for cells expressing major histocompatibility complex II?
Antigen is loaded into the rough endoplasmic reticulum of mostly intracellular peptides for cells expressing major histocompatibility complex I; for cells expressing major histocompatibility complex II, antigen is loaded in acidified endosomes
Which major histocompatibility complex mediates viral immunity?
Major histocompatibility complex I mediates viral immunity (via interaction with CD8+ T cells)
Which protein is paired with major histocompatibility complex I?
2 microglobulin
On cells that express major histocompatibility complex II, where is antigen loaded into the peptide-binding groove?
Antigen is loaded in acidified endosomes
Which human leukocyte antigen subtype is associated with psoriasis, ankylosing spondylitis, inflammatory bowel disease, and Reiter’s syndrome?
B27
Which four autoimmune-related conditions are associated with human leukocyte antigen subtype B27?
Psoriasis, Ankylosing spondylitis, Inflammatory bowel disease, and Reiter’s syndrome (remember: PAIR
Which human leukocyte antigen subtype is associated with Graves’ disease?
B8
Which human leukocyte antigen subtype is associated with multiple sclerosis, hay fever, systemic lupus erythematosus, and Goodpasture’s syndrome?
DR2
Which two human leukocyte antigen subtypes are associated with type 1 diabetes mellitus?
DR3 and DR4
Which human leukocyte antigen subtype is associated with rheumatoid arthritis?
DR4
Which human leukocyte antigen subtype is associated with pernicious anemia and Hashimoto’s thyroiditis?
DR5
Which human leukocyte antigen subtype is associated with steroid-responsive nephrotic syndrome?
DR7
Which human leukocyte antigen subtype is associated with hemochromatosis?
A3
What is the primary function of B cells?
To make antibodies
Which types of organ graft rejections are mediated by B cells? By T cells?
B cells mediate hyperacute organ graft rejection; T cells mediate acute and chronic organ graft rejection
Do immunoglobulin G antibodies bind to bacteria, viruses, or both?
Both; immunoglobulin G opsonizes bacteria and inactivates viruses by binding them
Which immunoglobulin mediates allergic reactions (type I hypersensitivity)?
Immunoglobulin E
Which hypersensitivity reactions are mediated by immunoglobulin G?
Type II and type III hypersensitivity reactions
What are the primary functions of CD4+ T cells?
To induce B cells to make antibodies; to produce γ-interferon to activate macrophages
Which T cells are cytotoxic to cells infected by viruses?
CD8+ cells
Which immune cells mediate type IV hypersensitivity reactions?
T cells
Which three cytokines enhance activity of natural killer cells?
Interleukin-12, interferon-, and interferon-
Which two signals induce natural killer cell killing activity?
Exposure to the activation signal on infected target cells; absence of major histocompatibility complex I on the target cell surface
Natural killer cells exhibit killing activity against which two types of cells?
Virally infected cells and tumor cells
Natural killer cells use _____ and _____ to induce apoptosis in target cells.
Perforins and granzymes
Helper T cells have CD4, which helps them bind to major histocompatibility complex ___ (I/II) on antigen-presenting cells.
Major histocompatibility complex II
Cytotoxic T cells have CD 8, which binds to major histocompatibility complex ___ (I/II) on virus-infected cells.
Major histocompatibility complex I
CD4 cells recognize major histocompatibility complex _____ (I/II), while CD8 cells recognize major histocompatibility complex _____ (I/II).
II; I
What is the CD3 complex?
A cluster of polypeptides involved in T-cell signal transduction
Name three antigen-presenting cells.
Macrophage, B cell, and dendritic cell
When macrophages and lymphocytes interact, each releases cytokines that stimulate the other. What are the cytokines?
Lymphocytes release interferon-γ and macrophages release interleukin-1 and tumor necrosis factor-
Which two species of gram positive bacteria produce superantigens?
Streptococcus pyogenes and Staphylococcus aureus
Bacterial superantigens cross-link _____ to _____.
T-cell receptors; major histocompatibility complex II
Which immune cells are involved in the body’s response to endotoxins on gram negative organisms?
Endotoxin directly stimulates macrophages
Which three cytokines are released as a result of superantigen-caused activation of macrophages?
Interleukin-1, interleukin-6, tumor necrosis factor-
Which subtype of helper T cell is activated by superantigens?
Th1 cells (which subsequently cause cytokine release from macrophages)
Which receptor does endotoxin bind to on macrophages?
CD14
Superantigen binding results in uncontrolled release of _____ from T cells.
Interferon-γ
In immune reactions, the presence of a costimulatory signal via B7 and CD28 interaction is important in the activation of what type of cell?
T cells
What is the first step in the activation of helper T cells by antigen-presenting cells?
Antigen-presenting cells present a phagocytosed foreign body to the helper T cell
Which molecule on the antigen-presenting cell surface presents foreign antigens to helper T cells?
Major histocompatibility complex II
During T-cell activation, what part of the helper T cell recognizes the foreign antigen?
The T-cell receptor recognizes antigens bound to major histocompatibility complex II of antigen-presenting cells
What is the origin of the proteins presented with major histocompatibility complex I molecules to cytotoxic T cells?
Proteins are endogenously synthesized and presented on major histocompatibility complex I
What part of the cytotoxic T cell recognizes the proteins that are presented on major histocompatibility complex I?
The T-cell receptor
In addition to the interaction of the major histocompatibility complex II and the T-cell receptor, what other interaction is required for T-cell activation?
The interaction of B7 and CD28 (this is signal 2 of T-cell activation)
What is the function of an activated helper T cell?
Synthesis and secretion of cytokines
What cytokine from helper T cells activates cytotoxic T cells to kill virus-infected cells?
Interleukin-2, which is the second signal required after the interaction of major histocompatibility complex I and T-cell receptors
Which type of helper T cell produces the cytokines that serve as a signal for B-cell class switching?
Th2 cells
Which three cytokines may serve as a signal in B-cell class switching?
Interleukin-4, interleukin-5, interleukin-6
In addition to cytokines released by helper T cells, what other signal is required for B-cell activation?
CD40 receptor binding to CD40 ligand on helper T cell
Which parts of the antibody light and heavy chains recognize antigen?
The variable sections
Which two antibody types fix complement?
Immunoglobulin M and Immunoglobulin G
What are the 4 C’s that are important to remember about the Fc fragment of an antibody?
Constant region, Carboxy terminal, Complement binding, and Carbohydrate side chains
Name four different mechanisms by which antibody diversity is generated.
The random recombination of VJ (light-chain) or VDJ (heavy-chain) genes, the random combination of heavy and light chains, somatic hypermutation, and the addition of nucleotides to DNA during genetic recombination by terminal deoxynucleotidyl transferase
What is the process called whereby an antibody promotes the phagocytosis of an antigen by a phagocyte?
Opsonization
What is the process called whereby an antibody attaches to an antigen and prevents adherence to cells?
Neutralization
Antibodies triggering the sequence that leads to the activation of the membrane attack complex have activated what part of the immune system?
Complement
When an antibody activates complement which two bacteria-killing processes are enhanced?
Opsonization and lysis
What part of the antibody binds complement?
The Fc fragment
What stimulus causes somatic hypermutation to generate antibody diversity?
Antigen stimulation
Which two immunoglobulin isotypes do mature B cells express on their surfaces?
Immunoglobulin M and immunoglobulin D
B cells can be induced to become which type of antibody-secreting cell?
Plasma B cells
Which signals mediate antibody class switching?
Cytokines and CD40 ligand
Which three classes of immunoglobulins do plasma cells secrete?
Immunoglobulin A, immunoglobulin E, and immunoglobulin G
Which immunoglobulin is the main antibody that is involved in the secondary response?
Immunoglobulin G
Which immunoglobulin is most abundant?
Immunoglobulin G
Which immunoglobulin fixes complement, crosses the placenta, opsonizes bacteria, and neutralizes bacteria toxins and viruses?
Immunoglobulin G
Which immunoglobulin prevents the attachment of bacteria and viruses to mucous membranes but cannot fix complement?
Immunoglobulin A
Which immunoglobulin is found in secretions?
Immunoglobulin A
How does the structure of immunoglobulin A differ in secretions vs plasma?
Immunoglobulin A can be either a monomer or a dimer
Which immunoglobulin is produced as part of the primary response to an antigen, fixes complement, but does not cross the placenta?
Immunoglobulin M
Which immunoglobulin is the antigen receptor on the surface of B cells?
Immunoglobulin M
Which immunoglobulin can be monomer or pentamer?
Immunoglobulin M
Which immunoglobulin has an unclear function and can be found on the surface of B cells and in serum?
Immunoglobulin D
Which immunoglobulin mediates immediate (type I) hypersensitivity by inducing the release of mediators from mast cells and basophils when an individual is exposed to an allergen?
Immunoglobulin E
Which immunoglobulin mediates immunity to helminths and has the lowest concentration in serum?
Immunoglobulin E
Which type of antibody activates eosinophils?
Immunoglobulin E
Immunoglobulin G molecules from two individuals represent two different _____ of the same class of immunoglobulins because they are encoded by two different alleles of the same gene.
Allotypes
Define antibody allotype and isotype.
Allotypes are genetic polymorphisms within the population; isotypes are the five heavy chains of antibodies
Are isotypes (immunoglobulin A, immunoglobulin E, etc) determined by the light chain or heavy chain?
Heavy chain
Two antibodies of the same allotype and isotype that bind different antigens are different _____.
Idiotypes
What region of the antibody accounts for the unique antigen binding site, which ultimately distinguishes between idiotypes?
Hypervariable region
How do the molecular structures of thymus-dependent and -independent antigens differ?
Thymus-dependent antigens lack the peptide component
Thymus-independent antigens stimulate release of which type of antibodies?
Immunoglobulin M only
How does the immune response to thymus-dependent and -independent molecules differ?
Only thymus-dependent antigens generate immunologic memory
An antigen lacking a peptide component cannot undergo which process that promotes antibody class switching and immunologic memory?
Thymus independent lack a peptide component, cannot be presented to T cells, do not promote isotype switching, and do not result in immunologic memory
Why is a peptide component added to the Haemophilus influenzae antigen used as a vaccine?
In vaccine form, Haemophilus influenzae is conjugated to protein, which makes it thymus dependent
This is an MHC class ____ (I/II) molecule, made of ____ and ____ chains, and expressed in ____ cells. It does not bind ____ (CD4/CD8/TCR).
MHC class II; α and β chains; antigen-presenting cells; CD8
This is an MHC class ____ (I/II) molecule, made of a(n) ____ chain paired with a(n) ____, and expressed in all cells except ____.
MHC class I; α chain; β2-microglobulin; red blood cells
