Immunology FINAL
How do high affinity IgG and IgA antibodies neutralize toxins and block parasite infectivity?
Bind surface proteins to inhibit cellular entry
Although the complement cascade can be initiated by antibodies bound to the surface of a pathogen, complement activation is generally considered to be an innate immune response. This is because:
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Amino acid sequence analysis of all of the peptides found in a single IgG antibody would reveal unique peptide sequences totaling ~600-700 amino acids. Using this estimate, the predicted molecular weight of an antibody protein would be ~70-75 kDa. Yet, an intact antibody protein has a molecular weight of ~150 kDa. The explanation for this discrepancy is:
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Both MHC class I molecules and MHC class II molecules that lack bound peptide are unstable.
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Differences between the genes encoding B cell receptors and those encoding T cell receptors reflect:
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How can overexpression of TNFα damage the host?
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Immunoglobulin isotypes are determined by the _________.
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In any given immunoglobulin molecule, the two heavy chains and the two light chains are ____________, giving an antibody molecule two identical antigen-binding sites.
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In cell culture experiments, purified B cells expressing IgM can be induced to switch to producing IgE by stimulating them with an antibody to CD40 (a stimulatory antibody) plus the cytokine IL-4. In an individual undergoing an immune response, these signals would normally be provided by:
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Individuals with defects in T cell development have a severe immunodeficiency disease called SCID (severe combined immunodeficiency disease). In these individuals, the absence of all T cells causes defects in both cell-mediated (T cell-based) and humoral (antibody-based) immune responses. The defect in antibody responses in SCID patients is due to:
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Infection and the responses to it can be divided into stages. The immune system responds to local infection and penetration of the epithelium, specifically by:
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Linked recognition between B and T cells ensures that:
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Lymphoid organs can be divided broadly into the central or primary lymphoid organs, where lymphocytes are generated, and the peripheral or secondary lymphoid organs, where mature, naive lymphocytes are maintained and adaptive immune responses are initiated. The central lymphoid organs are the:
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Mannose binding lectins (MBL) and ficolins are the two classes of proteins that can initiate the lectin pathway of complement activation. These proteins are selective for activating complement on the surfaces of microbial pathogens rather than host cells because:
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Many different NOD-like receptors, including several with pyrin domains and several with HIN domains, can function to trigger inflammasome assembly leading to the activation of caspase-1. The reason for many different sensors in this innate response system is that:
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One factor that is imperative to escalating any T cell activation is __________.
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Selectins are important for specifically guiding leukocytes to particular tissues, a phenomenon known as ________________.
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Strep throat is commonly caused by group A Streptococcus bacteria. A common symptom of strep throat is the presence of swollen lymph nodes in the neck. This symptom usually peaks about 2-4 days after the onset of the infection, and is due to:
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The cellular distribution of MHC class I versus MHC class II molecules is quite different, with MHC class II molecules generally expressed on a very limited set of cell types. This is because:
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The evolution of diverse mechanisms in microorganisms that prevent Fc region activity demonstrates that ____________.
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The exon encoding the V region of an immunoglobulin protein is generated by a process of somatic recombination. This recombination event brings V gene and J gene segments together:
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The figure below demonstrates which of the following principles? Red bars indicate a mutation in the amino acid sequence.
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The first pattern recognition receptor (PRR) important in innate immune responses was discovered in the fruit fly Drosophila melanogaster. Stimulation of this receptor, called Toll, induces:
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The great diversity of antigen receptors allows for hosts to:
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The pattern recognition receptors on cells of the innate immune system are genetically encoded, meaning that their sequences and specificities are determined prior to the development of the individual. In contrast, the antigen receptors of B and T lymphocytes arise from a random rearrangement process that occurs differently in each lymphocyte as it develops. One potential problem entailed by the random process that generates lymphocyte antigen receptors is the possibility that:
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There are two broad ways that the complement system uses to kill pathogens. The _______ method forms a membrane attack complex and destroys the target cell.
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Upon activation, CD4 T cells:
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Which is NOT a step of phagocytic respiratory burst?
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Which of the following is described as the intermediate form of B cells where they secrete antibody but retain substantial surface immunoglobulin and MHC class II molecules and so can continue to take up and present antigen to T cells?
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Which of the following is not true regarding immunoglobulin classes?
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While CD28 co-stimulation is important for the initial activation of naive T cells, other co-stimulatory molecules function at later stages of the T cell response. Several of these other co-stimulatory molecules are members of the TNF-receptor family, and function by activating the transcription factor, NFkB. Therefore, stimulation of these co-stimulatory TNF-receptors on activated T cells is likely to:
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__________ opens DNA hairpins during somatic recombination, generating palindromic P-nucleotides.
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Which of the following is NOT a strategy used by hosts to deal with the threat posed by microbes?
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What is meant by the 12/23 rule?
A gene segment flanked by an RSS with a 12 bp spacer can only be joined to one with a 23 bp spacer
IgM is the first antibody isotype secreted following activation of a naive B cell. IgM is found at high concentrations in the serum, and is found as a very high molecular weight complex. This high molecular weight complex is composed of:
A pentamer of IgM monomers
What are the two classes of T cells?
CD8 and CD4
_________ initiate(s) mutations in somatic hypermutation, gene conversion, and class switching.
Activation-induced cytidine deaminase (AID)
Immunodeficiency diseases occur when individuals have defects in leukocyte adhesion to inflamed endothelial cells, thereby impeding the extravasation of phagocytes into infected tissues. When neutrophils from one class of these patients were isolated and tested using in vitro assays for neutrophil-endothelial cell interactions and extravasation, it was found that the neutrophils could slowly roll along the endothelial vessel wall but were unable to arrest and migrate across the endothelium. The most likely protein deficient in these neutrophils is:
An integrin
The vaccine to Haemophilus influenzae type b is called a conjugate vaccine. It is composed of the tetanus toxoid protein conjugated to the capsular polysaccharide of the H. influenzae type b bacteria. When used to vaccinate infants, the antibody response generated by this vaccine would include:
Antibodies to the bacterial polysaccharide and the tetanus toxoid
In some vertebrates, such as rays and some shark species, immunoglobulin light chain genes consist of multiple units of already rearranged VJ-C genes, of which one is chosen for expression in a developing B cell. This strategy may have evolved in these organisms:
As a means to generate a rapid response to common pathogens encountered by these animals
Whereas B and T cells differ markedly in their functions during an immune response, the two lymphocyte subsets share the enzymatic machinery and overall scheme for generating antigen receptor diversity. This is because:
B cells and T cells both need enormous antigen receptor diversity to provide protection against the diversity of pathogens.
The first signal required for B-Cell activation is delivered through the _________.
B-Cell antigen receptor
Which of the following is INCORRECT regarding the Secondary Immune Response?
Has a higher concentration of IgM antibodies than IgG
Which of the following is NOT one of the 5 main classes of immunoglobulins in humans?
IgF
When macrophages in a tissue encounter bacteria, they release cytokines that induce an inflammatory response. These cytokines act on other immune cells to recruit them to the site of infection and to enhance their activities. In addition, these cytokines act on the endothelial cells of the blood vessel wall to:
Increase their permeability, allowing fluid and proteins to leak into the tissue
Chemokines such as CXCL8 have a key role in the rapid recruitment of neutrophils to the site in the tissue containing the focus of an infection. In this response, CXCL8 has two different functions. In addition to inducing integrin activation on the neutrophil, CXCL8 also functions to:
Induce directional migration of the neutrophil in the tissue
The antigen receptor on a T cell recognizes a degraded fragment of a protein (i.e., a peptide) bound to a specialized cell surface peptide-binding receptor called an MHC molecule. One key aspect of this system is that the peptides displayed on MHC molecules can be derived from intracellular proteins. This mode of antigen recognition is particularly important in allowing the adaptive immune response to detect infections by:
Intracellular pathogens, such as viruses and some protozoa
Linked recognition requires presentation of the appropriate peptide by _______ molecules on the B cell surface.
MHC class II
The skin and bodily secretions provide the first line of defense against infection. One response in this category that is common during upper respiratory virus infections is:
Mucus production
______ is the terminal form of an activated B cell that secretes specific immunoglobulins.
Plasma cell
When complement proteins are covalently deposited onto the surface of a bacterium, this can sometimes lead to direct lysis of the bacterium. However, more commonly, the deposition of complement proteins onto the bacterial surface does not directly harm the bacterium. Instead, these complement proteins aid in bacterial elimination by:
Providing a mechanism for phagocytes bearing complement receptors to recognize and ingest the bacterium
Which evolutionary adaptation allows for hosts to produce millions of antibodies highly specific to unique antigens?
Somatic DNA recombination during B cell development
Because HIV selectively targets and kills____________, people become vulnerable to parasites that they'd otherwise control easily.
T cells
In contrast to the immunoglobulins, which interact with pathogens and their toxic products in the extracellular spaces of the body, ___________ recognize foreign antigens only when they are displayed on the surface of the body's own cells.
T cells
Stimulation of the nucleic acid sensing TLRs that reside in endosomal membranes induces the production of a different cytokine response than is produced by stimulation of the plasma membrane TLRs. In part, this distinction is based on the different adapter proteins used by the nucleic acid sensing TLRs, leading to the activation of IRF factors. The cytokine response following stimulation of nucleic acid-sensing TLRs is characterized by production of:
The antiviral cytokine, type I interferon
Which of the following best explains why specialized sites are required for linked recognition to occur?
The chance of randomly encountering a matching naïve lymphocyte for a particular antigen in circulation is extremely low
The best evidence supporting the concept of immunological memory is:
The increased rapidity and magnitude of the secondary response to the same antigen
Given the enormous heterogeneity of antigen receptors expressed on the populations of naive B and T lymphocytes, the adaptive immune response relies on a process whereby the rare lymphocyte that binds to the antigen is first induced to proliferate, before it can perform its effector function. For B cells, there is a clever mechanism that ensures that the specificity of the antibody secreted by the plasma cell will recognize the same pathogen that initially stimulated the B cell antigen receptor and induced B cell proliferation. This mechanism is:
The naive B cell expresses a membrane-bound form of the antibody as a receptor, and secretes that same antibody when it differentiates into a plasma cell.
Some Pattern Recognition Receptors (PRRs) recognize nucleic acids, like RNA or DNA. Since our own cells contain human RNA and DNA, the activation of innate immune pathways by these PRRs must rely on additional criteria to discriminate self from nonself. Additional criteria include everything EXCEPT:
The presence of adenosine residues in viral RNA
At each amino acid position, the degree of variability is the ratio of the number of different amino acids seen in all of the sequences together to the frequency of the most common amino acid.
True
B cells deal with pathogens and their protein products circulating within the body; secretion of a soluble antigen-recognition molecule enables the B cell to act in the clearance of antigen effectively throughout the extracellular spaces of the body.
True
Dendritic cells are tissue resident myeloid cells that are highly phagocytic, like macrophages. However, dendritic cells do not play a major role in large-scale pathogen destruction; instead, they are important in initiating adaptive immune responses of T cells.
True
Each family of NK cell receptors has members that promote NK cell activation, and members that send inhibitory signals when engaged. The difference between activating and inhibitory receptors lies in their association with accessory proteins that promote downstream signaling, or in their ability to recruit and activate inhibitory phosphatases, respectively.
True
Each individual B cell has the ability to recognize just one specific antigen
True
Several pathogens produce proteins, either membrane-bound or secreted, that inactivate C3b that might be deposited on the pathogen surface. C3b is specifically targeted due to its central position in all three complement pathways.
True
The C3 convertase of the alternative complement pathway amplifies the overall magnitude of complement activation regardless of which of the three pathways initiated the complement activation initially.
True
The inflammatory response is characterized by four classic symptoms: heat, redness, pain, and swelling. In some instances, this response can be triggered by stimuli that are non-infectious such as asbestos, a process known as 'sterile inflammation.' When exposure to the stimulating trigger is persistent, a state of chronic inflammation can result. This process is likely to be detrimental to the health of the host.
True
Unlike innate immune responses, adaptive immune responses are initiated in secondary lymphoid organs. However, the innate immune response to an infection in a tissue has a pivotal role in inducing T-cell responses in the nearest lymph node by activating tissue dendritic cells and inducing their migration to the lymph node.
True
Vaccination against many infectious diseases has provided enormous benefit in developed countries, leading to the virtual eradication of diseases such as polio, measles, smallpox, and others. However, efforts to create long-lasting vaccines against some viral infections, like Influenza and HIV, have not been successful to date because:
Viruses like HIV and Influenza undergo antigenic variation to evade previous immune responses.
The germinal center is a region within the secondary B cell follicle where sustained B cell proliferation and differentiation take place. The processes of B cell proliferation and differentiation, including affinity maturation and class switching, require periodic interactions of the germinal center B cells with CD4 TFH cells. These periodic interactions between the B cells and TFH cells can occur:
When B cells cycle between the dark zone and the light zone of the germinal center
Which of the following statements is TRUE regarding the germinal center?
Within the germinal center, B cells begin their differentiation into antibody secreting plasma cells and/or memory B cells.
The ___________ pathway can be initiated by spontaneous hydrolysis and activation of the complement component C3, which can then bind directly to microbial surfaces.
alternative
When produced in large amounts or injected systemically, C3a and C5a induce a generalized circulatory collapse, producing a shocklike syndrome similar to that seen in a systemic allergic reaction involving antibodies of the IgE class. Such a reaction is termed ______________.
anaphylactic shock
MHC class II molecules are normally found on dendritic cells, B lymphocytes, and macrophages (i.e., _______________ cells), but not on other tissue cells.
antigen-presenting
Lysozyme digests the cell walls of Gram-positive and Gram-negative _______________.
bacteria
All the cellular elements of the blood, including the cells of the immune system, arise from pluripotent hematopoietic stem cells in the _____________.
bone marrow
The process of ______________ allows selected B cells to produce antibodies with a variety of different effector functions.
class switching
Which of the following complement pathways can be activated by interaction with antibodies?
classical
The differential actions of the immune system to TI-1 antigens allows the host to __________.
coordinate the antibody response to the magnitude of the threat
The cytokine IL-10 is unique in a sense as its primary role is to:
dampen inflammation
T-cell responses are initiated in secondary lymphoid organs by activated _______________.
dendritic cells
Dendritic cells are important antigen-presenting cells because of the:
diversity of pathogens about which they can communicate information
Some follicles in the spleen may contain _______________, in which B cells involved in an adaptive immune response are proliferating and undergoing somatic hypermutation
germinal centers
Which of the following best describes the classical complement pathway?
it was the first complement cascade to be discovered
Which of the following is the site at which B and T cells interact?
secondary lymphoid tissues
The T cell maturation process selects cells with receptors (TcR) that can recognize non-self but not____________.
self-antigens
Recent insights into adaptive immune responses in other phyla have highlighted ______
that many other species have evolved similar mechanisms to sense many diverse antigens
Which of the following is NOT one of the three main effector functions of antibodies?
they can directly kill pathogens by releasing cytotoxic granules
The production of antimicrobial peptides is one of the most evolutionarily ancient mechanisms of defense for multicellular organisms, and most eukaryotic species make many different forms of these proteins. For instance, human Paneth cells in the gastrointestinal epithelium make 21 different defensins. The reason for this diversity of antimicrobial peptides is:
Each one has distinct activities against Gram-negative bacteria, Gram-positive bacteria, or fungi.
B cells express a complement receptor that binds to C3b cleavage products, such as iC3b and C3dg. When a B cell with an antigen receptor that specifically recognizes that pathogen also has its complement receptor stimulated because the pathogen is opsonized with these C3 fragments, B cell activation is greatly enhanced. Due to this mechanism, B cells can be activated by much lower concentrations of antigen (in this case, the pathogen) than if the antigen is devoid of complement components. This mechanism functions to:
Ensure that pathogens are readily detected by the adaptive immune system before they replicate to high levels in the host
All mammalian TLRs have been shown to directly bind to microbial products, leading to TLR signaling.
False
CD8 cytotoxic T cells are specialized to kill extracellular pathogens.
False
Each IgG molecule consists of two heavy chains and four light chains.
False
Of all the granulocytes, neutrophils have the least phagocytic activity.
False
Once B cells begin secreting antibodies, they cease dividing and have a life-span of only a few days.
False
T cells recognize free floating antigens in circulation.
False
The acute phase response contributes to infection control by producing molecules that promote pathogen opsonization and complement activation. This response is only induced by direct action of microbial components on hepatocytes in the liver.
False
The innate immune response together with antibodies are generally not effective at clearing infections established by pathogens that replicate inside host cells. The evolution of T cells has provided a means for the immune response to 'see' intracellular infections based on the ability of T cells to:
Recognize pathogen-derived peptides on host MHC surface molecules
________ guides the rearrangement of immunoglobulin gene segments.
Recombinant signal sequences
Antibodies contribute to immune responses by each of the following mechanisms EXCEPT:
Recombination
