Addition of immunoglobulin G (IgG) specific for hemoglobin to a solution of hemoglobin results in the formation of a redprecipitate. In contrast, addition of the Fab fragments from this antibody to hemoglobin results in no such precipitate.What could explain this difference in results?Treatment with papain produces Fab fragments with different antigen specificity than the original IgG molecule.IgG can simultaneously bind two different antigens, whereas an Fab fragment can only bind one antigen at a time.The Fab fragments preferentially bind to other Fab fragments rather than to hemoglobin.The hemoglobin molecule antibody-binding sites can bind IgG molecules, but cannot bind Fab fragments.

Antibodies are proteins that are produced by the immune system to recognize and neutralize foreign…

Answered: Addition of immunoglobulin G (IgG)…

Biochemistry

9th Edition

ISBN:9781319114671

Author:Lubert Stryer, Jeremy M. Berg, John L. Tymoczko, Gregory J. Gatto Jr.

Publisher:Lubert Stryer, Jeremy M. Berg, John L. Tymoczko, Gregory J. Gatto Jr.

Chapter1: Biochemistry: An Evolving Science

Section: Chapter Questions

Problem 1P

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Generally, polysaccharides are not good antigens, because B cells that recognize them cannot get T-cell help. But for some pathogens, such as Streptococcus pneumoniae opsonization by antibodies that bind the thick polysaccharide "capsule" layer surrounding the bacteria is the major mechanism of clearing the infection. As expected, a pure polysaccharide vaccine is not terribly effective, but much better immunity is achieved by vaccinating with a polysaccharide covalently linked "conjugated" to an unrelated protein. Explain how this conjugate vaccine allows B cells capable of making anti-polysaccharide antibodies.
Serum from individuals with high levels of antibody to SARS-CoV2 has been used to treat patients with severe COVID-19. What is ONE way (there are several) that passive immunization with the antibody to the virus could help these patients? HINT: think about what opsonization with antibody could do for the innate immune response.
CD8 T cells in a culture are analyzed for their ability to produce the cytokine IFN-g, and the numbers of IFN-g-producing CD8 T cells are quantified. As a control, T cells are also stimulated with an irrelevant non-viral peptide (ova) plus dendritic cells. The results are shown in the figure below. Why is the T cell response different between the two lymph node populations?
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 current view in the field of immunology is that dendritic cells are the primary antigen-presenting cells for stimulating naive T cells. One piece of evidence supporting this conclusion is the observation that IRF8-deficient individuals, which retain their tissue-resident macrophages, are susceptible to a range of severe opportunistic infections caused by intracellular bacteria, viruses, and fungi. Explain the reasoning behind this argument.
A ‘B’ lymphocyte demonstrates ‘B cell receptors’ on its surface. These receptors have ‘variable’ regions which match the variable regions of the antibodies released by the plasma cell (formed by the activated B lymphocyte). Which of the following types of antibodies forms these ‘B cell receptors’ ? IgG IgA IgD IgE
Different classes of immunoglobulins are distinguished by the structure of their heavy chain constant regions. 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 single IgM monomer plus monomers of IgA and IgG A single IgM monomer bound to several non-immunoglobulin serum proteins A single IgM monomer bound to serum complement components A pentamer of IgM monomers Two dimers of IgM plus IgD forming a tetrameric complex
The least abundant immunoglobulin is IgE, for a good reason. Explain what the reason might be
It was stated that Rh antigens are so sparsely scattered in the red cell surface that IgG molecules bound to the Rh antigens are too far apart to fix C1q.Therefore, complement-mediated hemolysis cannot be invoked to explain hemolytic disease of the newborn. By what mechanism are the red cells destroyed?
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.
Surprisingly, humans as well as mice deficient in the complement protein, C3, have greatly reduced antibody responses to T cell-dependent antigens, and are impaired in their ability to control HSV infections. When C3-deficient mice are infected with HSV, once at day 0 and then a second time 4 weeks later, their antibody response is altered compared to wild-type mice, as shown in the figure #3 below. a) What is a likely explanation for the altered antibody response in the absence of complement C3? For fugure #4: For this experiment, mice are infected with varying doses of the HSV-rd virus, and peak IgG responses to the viral surface glycoproteins are measured. The results are shown in the fugure #4. b) What is the most likely explanation for these data? Do these results impact your answer to the part above (a)? Explain your reasoning.
Borrelia hermsii is a spirochete bacterium, transmitted by tick bites, that causes an illness characterized by a relapsing fever. The bacteria enter the host bloodstream and replicate there. Studies in mice show that episodes of bacteremia (bacteria in the blood) are efficiently controlled by anti-bacterial antibodies, but interestingly, follicular B cells are not required for this response, nor is the response impaired by splenectomizing the mice (i.e., removing the spleen). Which B cells are most likely responsible for this antibody response?

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