USMLE Immunology

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What test is done to diagnose CGD?: Nitroblue tetrazolium reduction test (NBT). It is negative in patients with CGD because there is no production of oxygen radicals.
What is the valence of an Ig molecule equal to?: The number of Ags that the Ab can bind
What is the name of the process that ensures that each B cell produces only one heavy-chain variable domain and one light chain?: Allelic exclusion. It is to ensure that one B cell produces only one Ab.
What is the major Ab of the primary immune response?: IgM
What form of immunity is responsible for removal of intracellular infections?: Cell-mediated immunity
True or false? Direct fluorescent Ab test is used to detect Abs in a patient?: False. Direct tests detect Ags; indirect tests detect Abs.
What is the triad of Wiskott-Aldrich syndrome?: Thrombocytopenia, eczema, and immunodeficiency is the triad of this X-linked recessive disorder.
What complement factor deficiency leads to ⬢ Increased susceptibility to pyogenic infections?: C3 deficiency
What complement factor deficiency leads to ⬢ Recurrent gonococcal infections?: C5-C8 deficiency
What complement factor deficiency leads to ⬢ Leukocyte adhesion deficiency with poor opsonization?: C1, C2, or C4 deficiency
What complement factor deficiency leads to ⬢ Hereditary angioedema?: C1 inhibitor (C1-INH)
Which IgG cannot activate complement?: IgG4
Name the T-cell CD marker: ⬢ Essential for Ab isotype switching (for B cell binding): CD40 ligand
Name the T-cell CD marker: ⬢ Interacts with MHC class I molecules: CD8
Name the T-cell CD marker: ⬢ Expressed on all T cells and is needed as a signal transducer for the T cell receptor: CD3
Name the T-cell CD marker: ⬢ Interacts with MHC class II molecules: CD4
Name the T-cell CD marker: Is a costimulatory molecule in T cell activation: CD28
What three cells are essential for T-cell differentiation in the thymus?: Dendritic cells, macrophages, and thymic epithelial cells
What is the only specific Ag-presenting cell?: B cells; macrophages and dendritic cells are nonspecific.
What is the tetrad of Jarisch-Herxheimer reaction?: Rigors, leukopenia, decrease in blood pressure, and increase in temperature
What is the name of the B cell that secretes Ig?: Plasma cell (mature B lymphocyte)
What would be the result if an Ab were cleaved with papain?: There would be two Fab and Fc regions.
What is the bone marrow maturation time for a phagocytic cell?: 14 days
Which leukotrienes are associated with the late-phase inflammatory response?: LTC4 and LTD4
What is the term for the strength of the association between Ag and an Ab?: Affinity (one of each)
True or false? More Ag is needed to produce a secondary immune response than a first immune response.: False. Fewer Ags are needed to trigger a secondary response.
What is the term for the strength of association between multiple Abbinding sites and multiple antigenic determinants?: Avidity (more than one binding site)
What Ig mediates ADCC via K cells, opsonizes, and is the Ig of the secondary immune response?: IgG
What test is used to detect anti-RBC Abs seen in hemolytic anemia?: Coombs test
What subset of T cells recognizes the MHC class I Ags?: CD8+ T cells (cytotoxic)

Remember, 8Ã—1=8 (CDÃ—8Ã—MHC class I=8); 4Ã—2=8 (CDÃ—4 MHC class II 8)
What cell surface marker is found on activated helper T cells?: CD40
What are the five Ig isotypes?: IgA, IgD, IgE, IgG, and IgM
Which integrin mediates the adhesion to endothelial cells for migration in and out of the blood during an immune response?: Beta2-integrins
What type of hypersensitivity is an Ab-mediated response against our own cells, receptors, or membranes via IgG or IgM?: Type II hypersensitivity reaction
What is the term to describe the limited portion of an Ag that is recognized by an Ab?: Antigenic determinant (epitope)
What cytokine do Th1 cells secrete to inhibit Th2 cell function?: INF-gamma
What three cells are essential for T-cell maturation?: Thymic epithelial cells, dendritic cells, and macrophages
What is the term for a single isolated antigenic determinant?: Hapten (not immunogenic)
What are the two opsonizing factors?: The Fc region of IgG and C3b
What is the most common Ig deficiency?: IgA deficiency; patients commonly present with recurrent sinopulmonary infections and GI disturbances.
What is the name of the B cellâ€“rich area of the spleen?: Primary follicle (in the white pulp)
What IL, produced by macrophages, is chemotactic for neutrophils?: IL-8. It not only is chemotactic, it also acts as an adhesive for neutrophils.
What Ig prevents bacterial adherence to mucosal surfaces?: IgA
What are the three rules of clonal selection?: 1. One cell type
2. One Ab type
3. Random selection of hypervariable regions, and only cells with bound Ag undergo clonal expansion
What is a plasma cell's life expectancy?: 7 to 14 days
What are defined by Ag-binding specificity?: Idiotypes
What type of binding occurs with one Fab or one idiotype of IgG?: Affinity
What molecule that is needed to trigger T cell activation is noncovalently linked to TCR?: CD3 molecule. It transmits signals to the inside of the T cell to trigger activation
What is the term for Ags that activate B cells without T-cell signaling?: Thymus-independent Ags
What are the three rules governing a secondary immune response?: 1. Covalent bonding between the hapten and carrier
2. B-cell exposure to hapten twice
3. T-cell exposure to carrier twice
What type of hypersensitivity is a T cell-mediated response to Ags that are not activated by Ab or complement?: Type IV hypersensitivity reaction (delayed type because of the 48â€“96 hour latency)
Name the macrophages by location: ⬢ Liver: Kupffer cells
Name the macrophages by location: ⬢ Lungs: Alveolar macrophages
Name the macrophages by location: ⬢ CNS: Microglial cells
Name the macrophages by location: ⬢ Kidney: Mesangial macrophages
What is the first human disease successfully treated with gene therapy?: Adenosine deaminase (ADA) deficiency
What receptors are the best markers for NK cells?: CD16 and CD56
True or false? Ag-Ab binding is irreversible: False. It is reversible because the Ags and Abs are not linked covalently.
What three major cell lines participate in the acquired immune system?: T cells, B cells, and macrophages
What test is used to screen for HIV?: ELISA. It detects anti-p24 IgG.
During what stage of B-cell development is IgM first seen on the surface?: Immature B cells
What Ig is responsible for Antibody-Dependent Cell-mediated Cytotoxicity of parasites, has a high-affinity Fc receptor on mast cells and basophils, and is responsible for the allergic response?: IgE
True or false? B-cell Ag receptors can be secreted.: True. B cell antigen receptors are Abs.
Are more Abs produced in a primary or a secondary immune response?: More Ab is produced in less time in a secondary immune response (shorter lag period).
By which process do Abs make microorganisms more easily ingested via phagocytosis?: Opsonization
What MHC class acts to remove foreign Ags from the body?: MHC class II Ags. This is accomplished via CD4 T cells.
What disorder is characterized by autoantibodies to IF?: Pernicious anemia
What cytokines do Th2 cells secrete to inhibit Th1 cell function?: IL-4, IL-10, and IL-13
What is the term for the number of Ag-binding sites on an Ig?: Valence
Which major cell type is found in the red pulp of the spleen?: RBCs. That is why it is called red pulp.
What is the name of the pathway that produces leukotrienes?: Lipoxygenase pathway, from arachidonic acid
What is the term to describe basophils that have left the bloodstream and entered a tissue?: Mast cells
What are the three major functions of secretory IgA?: 1. IgA receptor
2. Transport of IgA across epithelial barriers
3. Protection of IgA from degradative proteases
What IL is important in myeloid cell development?: IL-3 (3 face down is an M)
What is the term for different classes and subclasses of the same gene products?: Isotypes
What is the first Ab a baby makes?: IgM
What test, by using specific Abs to different receptors, allows for rapid analysis of cell types in a blood sample?: Flow cytometric analysis
What is the name of the T cellâ€“rich area of the spleen?: PALS (Parietolateral lymphocytic sheath)
What three complement fragments are also anaphylatoxins?: C3a, C4a, and C5a
Name the B-cell CD marker: ⬢ Required for class switching signals from T cells: CD40
Name the B-cell CD marker: ⬢ Receptor for EBV: CD21; it is a complement receptor for cleaved C3
Name the B-cell CD marker: ⬢ Used clinically to count B cells in blood: CD19
What immunologic test checks for a reaction between Abs and a particular Ag? (hint: ABO typing): Agglutination test
Which leukotriene is chemotactic for neutrophils?: LTB4
What Ig is associated with mucosal surfaces and external secretions?: IgA
What are the genetic variants of a molecule within members of the same species?: Allotypes
What cytokine do CD4 T cells secrete to activate B cells when the specific peptide in the groove of the MHC II molecule interacts with the TCR?: IL-4 is secreted to activate B cells. This begins the second step in the immune response, known as Activation. CD4 T cells secrete INF-alpha to activate macrophages
Which protein prevents internal binding of self proteins within an MHC class II cell?: Invariant chain
What would be the result if an Ab were cleaved with pepsin?: There would be a Fab' region; thus, it would still be able to participate in precipitation and agglutination.
Why are patients with Chronic Granulomatous Disease not prone to develop infections from catalase-negative bacteria?: Catalase-negative bacteria secrete H2O2 as a byproduct (remember, catalase breaks down H2O2), allowing the neutrophils to use it as the substrate for the other toxic metabolites. Patients with CGD are prone to catalase-positive bacterial infections.
What are the two chains of the TCR that are mainly found on the skin and mucosal surfaces?: gamma and delta chains
Which IL is associated with increases of IgG and IgE?: IL-4
What branch of the immune system is acquired in response to an Ag?: Adaptive branch. The adaptive branch of the immune system has a slow initiation with rapid responses thereafter.
True or false? T cells can recognize, bind, and internalize unprocessed Ags.: False. B cells recognize unprocessed Ags, but T cells can recognize only processed Ags.
What type of hypersensitivity is a result of high circulating levels of soluble immune complexes made up of IgG or IgM Abs?: Type III hypersensitivity reaction
At what stage of B-cell development can IgM or IgD be expressed on the cell surface?: Mature B cell; the memory B cell can have IgG, IgA, or IgE on its surface.
What T cell deficiency syndrome is associated with facial anomalies, hypoparathyroidism, thymic hypoplasia, and recurrent viral and fungal infections?: DiGeorge syndrome, which is due to a failure of the third and fourth pharyngeal pouch development. Remember, B cell deficiencies are associated with extracellular infection. T cell deficiencies are associated with intracellular infections
What is the stimulus for the classical pathway activation?: Ag-Ab complexes. The alternative pathway protects without use of Abs; the pathogen is the stimulus.
What is the first membrane-bound Ig on B cell membranes?: IgM; IgD follows shortly thereafter.
What region of the Ig does not change with class switching?: Hypervariable region
In MHC class II molecules, what chain blocks access to the peptide-binding groove during transportation within the cell, ensuring that the MHC class IIâ€“peptide complex is transported to the surface?: Invariant chain. This is essential because the CD4 T cells have antigen receptors only for peptides bound to the MHC II molecule. (MHC restriction)
What chromosome codes for HLA gene products?: The short arm of chromosome 6
What cells are atypical on a peripheral blood smear in heterophil-positive mononucleosis?: T cells, not B cells
What is the major Ig of the secondary immune response in the mucosal barriers?: IgA
What AR disorder is seen by age 1 to 2 with recurrent sinopulmonary infections, uncoordinated muscle movements, and dilation of the blood vessels?: Ataxia-telangiectasia
What are the four chemotactic agents?: 1. C5a
2. Leukotriene B4
3. IL-8
4. Bacterial peptides
What subset of CD4 helper T cells stimulate B-cell division and differentiation?: Th2
Which region of the variable domain comprises the Ag-binding site of the Ab?: Hypervariable region (three per light chain; three per heavy chain)
True or false? The increased oxygen consumption after phagocytosis is for ATP production.: False; it is for the production of toxic metabolites.
What is the limited portion of a large Ag that will actually be recognized and bound to an Ab and that contains approximately five to six amino acids or four to five hexose units?: Antigenic determinant (epitope). (Idiotypes bind to epitopes.)
What complement factor or factors are associated with ⬢ Chemotaxis?: C5a
What complement factor or factors are associated with ⬢ Membrane attack complex (MAC)?: C5â€“C9
What complement factor or factors are associated with ⬢ Opsonization?: C3b
What complement factor or factors are associated with ⬢ Anaphylaxis?: C3a, C4a, C5a
What happens to the Ab specificity when class switching occurs in mature B cells?: As the isotype is switched, the Ab specificity does not change because it does not affect the variable chains.
What IL down-regulates cell mediated immunity?: IL-10
Name the type of graft described by these transplants: ⬢ From one site to another on the same person: Autograft
Name the type of graft described by these transplants: Between genetically identical individuals: Isograft
Name the type of graft described by these transplants: ⬢ From one person to the next (the same species): Allograft
Name the type of graft described by these transplants: ⬢ From one species to another: Xenograft
What is the name of the process in which cells migrate toward an attractant along a concentration gradient?: Chemotaxis
What are the two functions of the thymus in T-cell differentiation?: Hormone secretion for T-cell differentiation and T-cell education to recognize self from nonself
What is the name of the T cellâ€“rich area of the lymph node?: Paracortex
What cell surface marker do all T cells have?: CD3
True or false? Patients with common variable hypogammaglobinemia have B cells in the peripheral blood.: True. Common variable hypogammaglobinemia first appears by the time patients reach their 20s and is associated with a gradual decrease in Ig levels over time.
What is the Ig associated with the primary immune response?: IgM
What MHC class of antigens do all nucleated cells carry on their surface membranes?: MHC class I antigens; they are also found on the surface of platelets.
What Ig is responsible for activation of complement, opsonization, and ADCC and is actively transported across the placenta?: IgG
What type of Ag do T cells recognize?: Processed antigenic peptides bound in the groove of the MHC molecule
What Ig is the major protective factor in colostrum?: IgA
What is the second cell involved in the immune response?: The CD4 T cell; the APC is the first cell in the immune response.
What is the term for thymic induction of T cells with high-affinity Ag receptors for self that are programmed to undergo apoptosis?: Negative selection. This helps to prevent autoimmune diseases.
What five main oxidizing reactions are used to kill ingested organisms?: 1. H2O2
2. Superoxide
3. Hydroxyl radical
4. Myeloperoxidase
5. Hypochlorous acid
What Ig is associated with ADCC for parasites?: IgE
True or false? RBCs do not have MHC class I Ags on their surface.: True. Remember, all nucleated cells (and platelets) have MHC class I Ags, and RBCs are not nucleated.
What Ig is associated with mast cell and basophil binding?: IgE. It attaches via receptor for the Fc region of the heavy epsilon chain
What IL do T cells secrete to induce T-and B-cell division?: IL-2. T cells express IL-2 receptors on their surface to induce self-expression.
Development of what T cell line follows low affinity for self-MHC class II Ags in the thymus?: CD4+T cells
What is the term for a substance secreted by a leukocyte in response to a stimulus?: Cytokine. If a cytokine affects another class of leukocytes, it is called an interleukin.
What subset of CD4 T cells is responsible for mast cell and eosinophil precursor proliferation?: Th2 cells
What are the four major functions of the acquired immune system?: 1. Recognize self from nonself
2. Amplify via cell division or complementation
3. Control the level of the response
4. Remove foreign material
What endotoxin receptor is the best marker for macrophages?: CD14
What is the term for the inherent ability to induce a specific immune response?: Immunogenicity; antigenicity refers to Ab/lymphocyte reaction to a specific substance.
What molecule differentiates the MHC class I from II Ag? (Hint: it's in the light chain.): The Beta-2-microglobin. It is the separately encoded Beta-chain for class I Ags.
What B cell disorder is characterized by pre-B cells in the bone marrow, no circulating B cells in plasma, normal cell-mediated immunity, low Igs, and appearance by 6 months of age?: Bruton X-linked hypogammaglobinemia. Tyrosine kinase deficiency leads to inadequate B cell maturation.
What subtype of IgG does not bind to staphylococcal A protein?: IgG3
What mast cell mediator is a chemotactic agent?: Eosinophil chemotactic factor A
What is the major Ig of the secondary immune response?: IgG
What T-cell surface projection recognizes and reacts to foreign Ags (presented by APCs)?: TCR
What is the confirmatory test for HIV?: Western blot
What is the name of the major chemotactic agent released from ⬢ Neutrophils?: Leukotriene B4 (LTB4)
What is the name of the major chemotactic agent released from ⬢ Macrophages?: IL-8 (IL-1 and TNF-gamma also)
What is the name of the major chemotactic agent released from ⬢ The blood serum? (Hint: it is a complement factor.): C5a
What is the name of the major chemotactic agent released from ⬢ Bacteria?: F-Met-Peptides
What cell surface marker is found on blood B cells?: CD19
What is the name of the B cellâ€“rich area in the lymph node?: Primary follicle of the cortex
What are the four ways to down-regulate the immune system?: 1. Decrease concentrations of Ag levels
2. Administer IgG in high concentrations
3. Inhibit B cells with Ag bound to IgG (complexes)
4. Turn off the original T or B cell with anti-Ab
What is the only Ig that crosses the placenta?: IgG
What is given to pregnant women within 24 hours after birth to eliminate Rh+ fetal blood cells from their circulation?: Rho (D) immune globulin (RhoGAM), an anti-RhD IgG antibody, prevents generation of RhD-specific memory B cells in the mother.
What IL is essential for lymphoid cell development?: IL-7 (A 7 upside down is an L; L is for Lymphoid)
What type of cell can never leave the lymph node?: Plasma cell
Via what pathway is glycolysis increased after phagocytosis?: HMP shunt
What is the term for a delay in the onset of normal IgG synthesis seen in the fifth to sixth month of life?: Transient hypogammaglobinemia of infancy; it usually resolves by age 16 to 30 months.
What subset of CD4 helper T-cell function is helping the development of CD8 T cells?: Th1; they are also responsible for delayed-type hypersensitivity (type IV)
What is the term for the strength of the association between Ags and Abs?: Avidity. There is a positive correlation between valence numbers and avidity.
What type of Ag do B cells recognize?: Free, unprocessed Ag
What Ig is associated with Ag recognition receptor on the surface of mature B cells?: IgD; IgM is also correct.
Which chromosome is associated with MHC genes?: Chromosome 6
What is the term for processing an APC's pinocytosed material by fusing with a lysosomal granule and cleaving the Ag into peptide fragments?: Ag processing; it is needed for class I molecules. Class II molecules have an invariant chain that protects them from breakdown.
What is the most common precipitin test used in clinical medicine?: Radial Immuno Diffusion (RID) for Ig levels.
What Ig activates the complement cascade most efficiently?: IgM
What assay is used to identify MHC class I molecules?: Microcytotoxic assay
Which IL increases IgA synthesis?: IL-5. It also stimulates eosinophil proliferation.
What is the term for an immunogenic agent that is too small to elicit an immune response?: Hapten; if it is coupled with a carrier, it may become immunogenic.
What type II hypersensitivity disorder is defined as ⬢ Autoantibodies directed against ACh receptors?: Myasthenia gravis
What type II hypersensitivity disorder is defined as ⬢ Autoantibodies directed against platelet integrin?: Autoimmune thrombocytopenia purpura
What type II hypersensitivity disorder is defined as ⬢ Autoantibodies against the type IV collagen in the basement membrane of the kidneys and lungs?: Goodpasture syndrome
What type II hypersensitivity disorder is defined as ⬢ Autoantibodies directed against the TSH receptor?: Graves disease
What type II hypersensitivity disorder is defined as ⬢ Autoantibodies directed against RBC Ag I?: Autoimmune hemolytic anemia
What Ig activates the alternate pathway, neutralizes bacterial endotoxins and viruses, and prevents bacterial adherence?: IgA
What enzyme is deficient in patients with CGD?: NADPH oxidase is deficient, resulting in an inability to produce toxic metabolites.
What subtype of IgG does not activate complement cascade?: IgG4
What two cell lines of the immune system do not belong to the innate branch?: T and B-cells belong to the adaptive branch, whereas PMNs, NK cells, eosinophils, macrophages, and monocytes belong to the innate branch.
What subset of T cells recognizes the MHC class II Ags?: CD4+ T cells (helper)
What T cell line arises from low affinity for self-MHC class I Ags in the thymus?: CD8+ T cells
What MHC class functions as a target for elimination of abnormal host cells?: MHC class I Ags (the endogenous pathway). This allows the body to eliminate tumor cells, virus-infected cellsâ€”anything the body recognizes as nonself via CD8+ T cells.
What are the three polymorphonuclear leukocytes? Be specific.: Neutrophils, eosinophils, and basophils
What disease is associated with the HLA-A3 allele: Primary Hemochromatosis
What diseases are associated with the HLA-B27 allele: Psoriasis, ankylosing spondylitis, inflammatory bowel disease, and Reiter's syndrome
What disease is associated with the HLA-DR2 and HLA-DR3 alleles: Systemic lupus erythematosus
What diseases are associated with the HLA-DR3 allele: Sjogren's syndrome, active hepatitis, systemic lupus erythematosus (with HLA-DR2) and type 1 diabetes (with HLA-DR4)
What diseases are associated with HLA-DR4: Rheumatoid arthritis and type 1 diabetes (with HLA-DR3)

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