Antibodies Quiz

PDF page 1470: Much of the information in this section is not within the scope for AP . Antibodies, also known as immunoglobulins, are proteins produced and secreted by plasma cells (differentiated B lymphocytes) that mediate the humoral immune response. Antibodies are Y-shaped proteins consisting of four polypeptides with at least two binding sites for a specific antigen. The

PDF page 1470: Much of the information in this section is not within the scope for AP . Antibodies, also known as immunoglobulins, are proteins produced and secreted by plasma cells (differentiated B lymphocytes) that mediate the humoral immune response. Antibodies are Y-shaped proteins consisting of four polypeptides with at least two binding sites for a specific antigen. The

PDF page 1470: Much of the information in this section is not within the scope for AP . Antibodies, also known as immunoglobulins, are proteins produced and secreted by plasma cells (differentiated B lymphocytes) that mediate the humoral immune response. Antibodies are Y-shaped proteins consisting of four polypeptides with at least two binding sites for a specific antigen. The

PDF page 1471: An antibody molecule is comprised of four polypeptides: two identical heavy chains (large peptide units) that are partially bound to each other in a “Y” formation, which are flanked by two identical light chains (small peptide units), as illustrated in

PDF page 1471: An antibody molecule is comprised of four polypeptides: two identical heavy chains (large peptide units) that are partially bound to each other in a “Y” formation, which are flanked by two identical light chains (small peptide units), as illustrated in

PDF page 1471: areas where the antigen is recognized on the antibody are variable domains and the antibody base is composed of constant domains. In germ-line B cells, the variable region of the light chain gene has 40 variable (V) and five joining (J) segments. An enzyme called DNA recombinase randomly excises most of these segments out of the gene, and splices one V segment to one J segment. During RNA processing, all but one V and J segment are spliced out. Recombination and splicing may result in

PDF page 1471: areas where the antigen is recognized on the antibody are variable domains and the antibody base is composed of constant domains. In germ-line B cells, the variable region of the light chain gene has 40 variable (V) and five joining (J) segments. An enzyme called DNA recombinase randomly excises most of these segments out of the gene, and splices one V segment to one J segment. During RNA processing, all but one V and J segment are spliced out. Recombination and splicing may result in

PDF page 1471: areas where the antigen is recognized on the antibody are variable domains and the antibody base is composed of constant domains. In germ-line B cells, the variable region of the light chain gene has 40 variable (V) and five joining (J) segments. An enzyme called DNA recombinase randomly excises most of these segments out of the gene, and splices one V segment to one J segment. During RNA processing, all but one V and J segment are spliced out. Recombination and splicing may result in

PDF page 1472: Figure 33.22 (a) As a germ-line B cell matures, an enzyme called DNA recombinase randomly excises V and J

PDF page 1470: areas where the antigen is recognized on the antibody are variable domains. For AP , you do not need to know the different classes of antibodies or the molecular structure of a specific antibody. What is important to understand is that antibodies are antigen-specific. When antibodies bind antigens, they can neutralize pathogens, mark them for phagocytosis, or activate the complement cascade. Because secreted antibodies can remain in the circulation for many years, secondary exposure to a pathogen results in a faster immune response. Antibodies occur in the blood, in gastric and mucus secretions, and in breast milk, thus providing passive immunity to the infant. Information presented and the examples highlighted in the section support concepts outlined in Big Idea 2 and Big Idea 4

PDF page 1470: areas where the antigen is recognized on the antibody are variable domains. For AP , you do not need to know the different classes of antibodies or the molecular structure of a specific antibody. What is important to understand is that antibodies are antigen-specific. When antibodies bind antigens, they can neutralize pathogens, mark them for phagocytosis, or activate the complement cascade. Because secreted antibodies can remain in the circulation for many years, secondary exposure to a pathogen results in a faster immune response. Antibodies occur in the blood, in gastric and mucus secretions, and in breast milk, thus providing passive immunity to the infant. Information presented and the examples highlighted in the section support concepts outlined in Big Idea 2 and Big Idea 4

PDF page 1473: Differentiated plasma cells are crucial players in the humoral response, and the antibodies they secrete are particularly significant against extracellular pathogens and toxins. Antibodies circulate freely and act independently of plasma cells. Antibodies can be transferred from one individual to another to temporarily protect against infectious disease. For instance, a person who has recently produced a successful immune response against a particular disease agent can donate blood to a nonimmune recipient and confer temporary immunity through antibodies in the donor’s blood serum. This phenomenon is called passive immunity; it also occurs naturally during breastfeeding, which makes breastfed infants highly resistant to infections during the first few months of life. Antibodies coat extracellular pathogens and neutralize them, as illustrated in Figure 33.24, by blocking key sites on the pathogen that enhance their infectivity (such as receptors that “dock” pathogens on host cells). Antibody neutralization can prevent pathogens from entering and infecting host cells, as opposed to the CTL-mediated approach of killing cells that are already infected to prevent progression of an established infection. The neutralized antibody-coated pathogens can then be filtered by the spleen and eliminated in urine or feces.

PDF page 1472: Similar to TCRs and BCRs, antibody diversity is produced by the mutation and recombination of approximately 300 different gene segments encoding the light and heavy chain variable domains in precursor cells that are destined to become B cells. The variable domains from the heavy and light chains interact to form the binding site through which an antibody can bind a specific epitope on an antigen. The numbers of repeated constant domains in Ig classes are the same for all antibodies corresponding to a specific class. Antibodies are structurally similar to the extracellular component of the BCRs, and B cell maturation to plasma cells can be visualized in simple terms as the cell acquires the ability to secrete the extracellular portion of its BCR in large quantities. Antibody Classes Antibodies can be divided into five classes—IgM, IgG, IgA, IgD, IgE—based on their physiochemical, structural, and immunological properties. IgGs, which make up about 80 percent of all antibodies, have heavy chains that consist of one variable domain and three identical constant domains. IgA and IgD also have three constant domains per heavy chain, whereas IgM and IgE each have four constant domains per heavy chain. The variable domain determines binding specificity and the constant domain of the heavy chain determines the immunological mechanism of action of the corresponding antibody class. It is possible for two antibodies to have the same binding specificities but be in different classes and, therefore, to be involved in different functions. After an adaptive defense is produced against a pathogen, typically plasma cells first secrete IgM into the blood. BCRs on

PDF page 1472: Similar to TCRs and BCRs, antibody diversity is produced by the mutation and recombination of approximately 300 different gene segments encoding the light and heavy chain variable domains in precursor cells that are destined to become B cells. The variable domains from the heavy and light chains interact to form the binding site through which an antibody can bind a specific epitope on an antigen. The numbers of repeated constant domains in Ig classes are the same for all antibodies corresponding to a specific class. Antibodies are structurally similar to the extracellular component of the BCRs, and B cell maturation to plasma cells can be visualized in simple terms as the cell acquires the ability to secrete the extracellular portion of its BCR in large quantities. Antibody Classes Antibodies can be divided into five classes—IgM, IgG, IgA, IgD, IgE—based on their physiochemical, structural, and immunological properties. IgGs, which make up about 80 percent of all antibodies, have heavy chains that consist of one variable domain and three identical constant domains. IgA and IgD also have three constant domains per heavy chain, whereas IgM and IgE each have four constant domains per heavy chain. The variable domain determines binding specificity and the constant domain of the heavy chain determines the immunological mechanism of action of the corresponding antibody class. It is possible for two antibodies to have the same binding specificities but be in different classes and, therefore, to be involved in different functions. After an adaptive defense is produced against a pathogen, typically plasma cells first secrete IgM into the blood. BCRs on