Antibody binding to a pathogen surface is greatly enhanced when both antigen-binding sites of the antibody are engaged at once, a feature known as bivalent binding. It is possible for antibodies to bind bivalently to a wide variety of components on many different pathogen surfaces due to the flexibility in the protein at the hinge region and at the V–C junction

Antibody binding to a pathogen surface is greatly enhanced when both antigen-binding sites of the antibody are engaged at once, a feature known as bivalent binding. It is possible for antibodies to bind bivalently to a wide variety of components on many different pathogen surfaces due to the flexibility in the protein at the hinge region and at the V–C junction

Human Heredity: Principles and Issues (MindTap Course List)

11th Edition

ISBN:9781305251052

Author:Michael Cummings

Publisher:Michael Cummings

Chapter17: Genes And The Immune System

Section: Chapter Questions

Problem 11QP: It is often helpful to draw a complicated pathway in the form of a flow chart to visualize the...

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It is often helpful to draw a complicated pathway in the form of a flow chart to visualize the multiple steps and the ways in which the steps are connected to each other. Draw the antibody-mediated immune response pathway that acts in response to an invading virus.
True/False: Antibody binding to a pathogen surface is greatly enhanced when both antigen-binding sites of the antibody are engaged at once, a feature known as bivalent binding. It is possible for antibodies to bind bivalently to a wide variety of components on many different pathogen surfaces due to the flexibility in the protein at the hinge region and at the V–C junction.
Antibody diversity is generated by multiple mechanisms, each of which contributes to the generation of antibodies with up to 1011 different amino acid sequences in their antigen-binding sites. Several of these mechanisms involve changes in the DNA sequences encoding the antibody heavy and light chain proteins. One mechanism that does not rely on changes to the DNA within the immunoglobulin heavy and light chain gene loci is, instead, dependent on: The contributions of amino acids from both the heavy chain and the light chain to form the antigen-binding site The random usage of V, D, and J gene segments to form the heavy chain V region sequence The random usage of k light chains versus l light chains to pair with the heavy chain The activity of TdT to add random nucleotides at the junctions between the V, J, and D region sequences The fact that heavy chain V regions contain an extra gene segment encoded by the D region compared to light chain V regions
Some pathogenic microorganisms encode proteins, such as the Staphylococcus Protein A, that bind to immunoglobulin constant region domains with high affinity. These microbial proteins provide a benefit to the microorganism by: Preventing antibodies bound to the microbe from binding to Fc receptors on phagocytes Blocking the binding of anti-microbial antibodies to the pathogen surface Cleaving the antibody into fragments that separate the antigen-binding region from the effector function Inducing aggregation of the anti-microbial antibodies by multivalent binding to the pathogen-derived protein Preventing the antibody from neutralizing the pathogen
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 Prevent B cells from being activated in response to antigens that are not pathogens Allow B cells to phagocytose the pathogen and help destroy it Induce increased rounds of B cell replication to make more pathogen-specific B cells Allow the B cell to block pathogen replication by interfering with multiple pathogen surface functions
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: Two of the three pathways for complement activation are initiated by constitutively produced recognition molecules that directly interact with microbial surfaces. When the complement cascade leads to the formation of a membrane-attack complex, the pathogen is killed. Several of the soluble products generated by complement activation lead promote the inflammatory response. Complement proteins bound to the pathogen promote uptake and destruction by phagocytic cells. The C3 convertase is only produced when complement activation is initiated by antibody binding to a pathogen.
Before the mechanism for generating antibody diversity had been established, a mechanism based on protein folding around an antigen was proposed, primarily by Linus Pauling. In this model, antibodies that had different specificities had the same amino acid sequence but were folded in different ways. Propose a test of this model.
Draw a schematic diagram of a typical IgG molecule and label each of the following parts: H chains, L chains, intrachain disulfide bonds, hinge, Fab, Fc, and all the domains. Indicate which domains are involved in antigen binding.
The classical complement pathway is initiated by C1q binding to the surface of a pathogen. In some cases, C1q can directly bind the pathogen, for instance by recognizing proteins of bacterial cell walls, but in most cases C1q binds to IgM antibodies that are bound to the pathogen surface. How does this IgM-binding feature of C1q contribute to rapid, innate immune responses rather than to slow, adaptive responses? C1q induces B lymphocytes to begin secreting antibody within hours of pathogen exposure. Natural antibody that binds to many microbial pathogens is produced prior to pathogen exposure. C1q binds to C-reactive protein which then binds to IgM on the pathogen surface. C1q directly induces inflammation, recruiting phagocytes and antibodies from the blood into the infected tissue. C1q binds to dendritic cells in the infected tissue, inducing them to secrete inflammatory cytokines.
What is the smallest unit of an antibody that can retain the specificity and binding affinity of the whole protein?
Which cleavage pattern (indicated by the red triangles in figure below) yields a fragment that has the same antigen-binding avidity as the intact antibody, but is unable to activate complement after binding to a pathogen?
What is the effect of the changes in the structure of the immunoglobulin G and its function of binding to and neutralizing/ tagging pathogens when there is an Increased production of metabolites in the blood that reduces its pH to < 6?