{"id":4322,"date":"2017-03-28T20:55:12","date_gmt":"2017-03-28T20:55:12","guid":{"rendered":"https:\/\/courses.lumenlearning.com\/wm-biology2\/?post_type=chapter&#038;p=4322"},"modified":"2024-04-26T02:31:46","modified_gmt":"2024-04-26T02:31:46","slug":"antibody-classes","status":"publish","type":"chapter","link":"https:\/\/courses.lumenlearning.com\/wm-biology2\/chapter\/antibody-classes\/","title":{"raw":"Antibody Classes","rendered":"Antibody Classes"},"content":{"raw":"<div class=\"textbox learning-objectives\">\r\n<h3>Learning Outcomes<\/h3>\r\n<ul>\r\n \t<li>Identify the different classes of antibodies<\/li>\r\n<\/ul>\r\n<\/div>\r\n<p id=\"fs-idp17788400\">Antibodies can be divided into five classes\u2014IgM, IgG, IgA, IgD, IgE\u2014based 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.<\/p>\r\n<p id=\"fs-idm60930656\">After an adaptive defense is produced against a pathogen, typically plasma cells first secrete IgM into the blood. BCRs on na\u00efve B cells are of the IgM class and occasionally IgD class. IgM molecules make up approximately ten percent of all antibodies. Prior to antibody secretion, plasma cells assemble IgM molecules into pentamers (five individual antibodies) linked by a joining (J) chain, as shown in Table 1.\u00a0The pentamer arrangement means that these macromolecules can bind ten identical antigens. However, IgM molecules released early in the adaptive immune response do not bind to antigens as stably as IgGs, which are one of the possible types of antibodies secreted in large quantities upon reexposure to the same pathogen.<\/p>\r\nThe following table summarizes the properties of immunoglobulins and illustrates their basic structures:\r\n<table>\r\n<thead>\r\n<tr>\r\n<th colspan=\"3\">Table 1.\u00a0The Five Immunoglobulin (Ig) Classes<\/th>\r\n<\/tr>\r\n<tr>\r\n<th>Name<\/th>\r\n<th>Properties<\/th>\r\n<th>Structure<\/th>\r\n<\/tr>\r\n<\/thead>\r\n<tbody>\r\n<tr>\r\n<td>IgA<\/td>\r\n<td>Found in mucous, saliva, tears, and breast milk. Protects against pathogens.<\/td>\r\n<td><img class=\"wp-image-3021 aligncenter\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/1223\/2017\/02\/09193235\/IgA.png\" alt=\"Two Y-shapes bound together at their tail ends.\" width=\"250\" height=\"95\" \/><\/td>\r\n<\/tr>\r\n<tr>\r\n<td>IgD<\/td>\r\n<td>Part of the B cell receptor. Activates basophils and mast cells.<\/td>\r\n<td><img class=\"wp-image-3022 aligncenter\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/1223\/2017\/02\/09193311\/Y-shape.png\" alt=\"A a single branching Y-shape\" width=\"98\" height=\"125\" \/><\/td>\r\n<\/tr>\r\n<tr>\r\n<td>IgE<\/td>\r\n<td>Protects against parasitic worms. Responsible for allergic reactions.<\/td>\r\n<td>\u00a0<img class=\"wp-image-3022 aligncenter\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/1223\/2017\/02\/09193311\/Y-shape.png\" alt=\"A a single branching Y-shape\" width=\"98\" height=\"125\" \/><\/td>\r\n<\/tr>\r\n<tr>\r\n<td>IgG<\/td>\r\n<td>Secreted by plasma cells in the blood. Able to cross the placenta into the fetus.<\/td>\r\n<td><img class=\"wp-image-3022 aligncenter\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/1223\/2017\/02\/09193311\/Y-shape.png\" alt=\"A a single branching Y-shape\" width=\"98\" height=\"125\" \/><\/td>\r\n<\/tr>\r\n<tr>\r\n<td>IgM<\/td>\r\n<td>May be attached to the surface of a B cell or secreted into the blood. Responsible for early stages of immunity.<\/td>\r\n<td><img class=\"wp-image-3023 aligncenter\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/1223\/2017\/02\/09193345\/IgM.png\" alt=\"A pentagon shape with branching tails coming from each corner.\" width=\"133\" height=\"125\" \/><\/td>\r\n<\/tr>\r\n<\/tbody>\r\n<\/table>\r\n<p id=\"fs-idp106928032\">IgAs populate the saliva, tears, breast milk, and mucus secretions of the gastrointestinal, respiratory, and genitourinary tracts. Collectively, these bodily fluids coat and protect the extensive mucosa (4000 square feet in humans). The total number of IgA molecules in these bodily secretions is greater than the number of IgG molecules in the blood serum. A small amount of IgA is also secreted into the serum in monomeric form. Conversely, some IgM is secreted into bodily fluids of the mucosa. Similar to IgM, IgA molecules are secreted as polymeric structures linked with a J chain. However, IgAs are secreted mostly as dimeric molecules, not pentamers.<\/p>\r\n<p id=\"fs-idm5112096\">IgE is present in the serum in small quantities and is best characterized in its role as an allergy mediator. IgD is also present in small quantities. Similar to IgM, BCRs of the IgD class are found on the surface of na\u00efve B cells. This class supports antigen recognition and maturation of B cells to plasma cells.<\/p>\r\n\r\n<h2>Antibodies of the Mucosal Immune System<\/h2>\r\nAntibodies synthesized by the mucosal immune system include IgA and IgM. Activated B cells differentiate into mucosal plasma cells that synthesize and secrete dimeric IgA, and to a lesser extent, pentameric IgM. Secreted IgA is abundant in tears, saliva, breast milk, and in secretions of the gastrointestinal and respiratory tracts. Antibody secretion results in a local humoral response at epithelial surfaces and prevents infection of the mucosa by binding and neutralizing pathogens.\r\n<div class=\"textbox tryit\">\r\n<h3>Try It<\/h3>\r\nhttps:\/\/assess.lumenlearning.com\/practice\/f5650687-040a-4899-836f-af22496018a7\r\n<\/div>","rendered":"<div class=\"textbox learning-objectives\">\n<h3>Learning Outcomes<\/h3>\n<ul>\n<li>Identify the different classes of antibodies<\/li>\n<\/ul>\n<\/div>\n<p id=\"fs-idp17788400\">Antibodies can be divided into five classes\u2014IgM, IgG, IgA, IgD, IgE\u2014based 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.<\/p>\n<p id=\"fs-idm60930656\">After an adaptive defense is produced against a pathogen, typically plasma cells first secrete IgM into the blood. BCRs on na\u00efve B cells are of the IgM class and occasionally IgD class. IgM molecules make up approximately ten percent of all antibodies. Prior to antibody secretion, plasma cells assemble IgM molecules into pentamers (five individual antibodies) linked by a joining (J) chain, as shown in Table 1.\u00a0The pentamer arrangement means that these macromolecules can bind ten identical antigens. However, IgM molecules released early in the adaptive immune response do not bind to antigens as stably as IgGs, which are one of the possible types of antibodies secreted in large quantities upon reexposure to the same pathogen.<\/p>\n<p>The following table summarizes the properties of immunoglobulins and illustrates their basic structures:<\/p>\n<table>\n<thead>\n<tr>\n<th colspan=\"3\">Table 1.\u00a0The Five Immunoglobulin (Ig) Classes<\/th>\n<\/tr>\n<tr>\n<th>Name<\/th>\n<th>Properties<\/th>\n<th>Structure<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>IgA<\/td>\n<td>Found in mucous, saliva, tears, and breast milk. Protects against pathogens.<\/td>\n<td><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-3021 aligncenter\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/1223\/2017\/02\/09193235\/IgA.png\" alt=\"Two Y-shapes bound together at their tail ends.\" width=\"250\" height=\"95\" \/><\/td>\n<\/tr>\n<tr>\n<td>IgD<\/td>\n<td>Part of the B cell receptor. Activates basophils and mast cells.<\/td>\n<td><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-3022 aligncenter\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/1223\/2017\/02\/09193311\/Y-shape.png\" alt=\"A a single branching Y-shape\" width=\"98\" height=\"125\" \/><\/td>\n<\/tr>\n<tr>\n<td>IgE<\/td>\n<td>Protects against parasitic worms. Responsible for allergic reactions.<\/td>\n<td>\u00a0<img loading=\"lazy\" decoding=\"async\" class=\"wp-image-3022 aligncenter\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/1223\/2017\/02\/09193311\/Y-shape.png\" alt=\"A a single branching Y-shape\" width=\"98\" height=\"125\" \/><\/td>\n<\/tr>\n<tr>\n<td>IgG<\/td>\n<td>Secreted by plasma cells in the blood. Able to cross the placenta into the fetus.<\/td>\n<td><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-3022 aligncenter\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/1223\/2017\/02\/09193311\/Y-shape.png\" alt=\"A a single branching Y-shape\" width=\"98\" height=\"125\" \/><\/td>\n<\/tr>\n<tr>\n<td>IgM<\/td>\n<td>May be attached to the surface of a B cell or secreted into the blood. Responsible for early stages of immunity.<\/td>\n<td><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-3023 aligncenter\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/1223\/2017\/02\/09193345\/IgM.png\" alt=\"A pentagon shape with branching tails coming from each corner.\" width=\"133\" height=\"125\" \/><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p id=\"fs-idp106928032\">IgAs populate the saliva, tears, breast milk, and mucus secretions of the gastrointestinal, respiratory, and genitourinary tracts. Collectively, these bodily fluids coat and protect the extensive mucosa (4000 square feet in humans). The total number of IgA molecules in these bodily secretions is greater than the number of IgG molecules in the blood serum. A small amount of IgA is also secreted into the serum in monomeric form. Conversely, some IgM is secreted into bodily fluids of the mucosa. Similar to IgM, IgA molecules are secreted as polymeric structures linked with a J chain. However, IgAs are secreted mostly as dimeric molecules, not pentamers.<\/p>\n<p id=\"fs-idm5112096\">IgE is present in the serum in small quantities and is best characterized in its role as an allergy mediator. IgD is also present in small quantities. Similar to IgM, BCRs of the IgD class are found on the surface of na\u00efve B cells. This class supports antigen recognition and maturation of B cells to plasma cells.<\/p>\n<h2>Antibodies of the Mucosal Immune System<\/h2>\n<p>Antibodies synthesized by the mucosal immune system include IgA and IgM. Activated B cells differentiate into mucosal plasma cells that synthesize and secrete dimeric IgA, and to a lesser extent, pentameric IgM. Secreted IgA is abundant in tears, saliva, breast milk, and in secretions of the gastrointestinal and respiratory tracts. Antibody secretion results in a local humoral response at epithelial surfaces and prevents infection of the mucosa by binding and neutralizing pathogens.<\/p>\n<div class=\"textbox tryit\">\n<h3>Try It<\/h3>\n<p>\t<iframe id=\"assessment_practice_f5650687-040a-4899-836f-af22496018a7\" class=\"resizable\" src=\"https:\/\/assess.lumenlearning.com\/practice\/f5650687-040a-4899-836f-af22496018a7?iframe_resize_id=assessment_practice_id_f5650687-040a-4899-836f-af22496018a7\" frameborder=\"0\" style=\"border:none;width:100%;height:100%;min-height:300px;\"><br \/>\n\t<\/iframe>\n<\/div>\n\n\t\t\t <section class=\"citations-section\" role=\"contentinfo\">\n\t\t\t <h3>Candela Citations<\/h3>\n\t\t\t\t\t <div>\n\t\t\t\t\t\t <div id=\"citation-list-4322\">\n\t\t\t\t\t\t\t <div class=\"licensing\"><div class=\"license-attribution-dropdown-subheading\">CC licensed content, Shared previously<\/div><ul class=\"citation-list\"><li>Biology 2e. <strong>Provided by<\/strong>: OpenStax. <strong>Located at<\/strong>: <a target=\"_blank\" href=\"http:\/\/cnx.org\/contents\/185cbf87-c72e-48f5-b51e-f14f21b5eabd@10.8\">http:\/\/cnx.org\/contents\/185cbf87-c72e-48f5-b51e-f14f21b5eabd@10.8<\/a>. <strong>License<\/strong>: <em><a target=\"_blank\" rel=\"license\" href=\"https:\/\/creativecommons.org\/licenses\/by\/4.0\/\">CC BY: Attribution<\/a><\/em>. <strong>License Terms<\/strong>: Access for free at https:\/\/openstax.org\/books\/biology-2e\/pages\/1-introduction<\/li><\/ul><\/div>\n\t\t\t\t\t\t <\/div>\n\t\t\t\t\t <\/div>\n\t\t\t <\/section>","protected":false},"author":17,"menu_order":15,"template":"","meta":{"_candela_citation":"[{\"type\":\"cc\",\"description\":\"Biology 2e\",\"author\":\"\",\"organization\":\"OpenStax\",\"url\":\"http:\/\/cnx.org\/contents\/185cbf87-c72e-48f5-b51e-f14f21b5eabd@10.8\",\"project\":\"\",\"license\":\"cc-by\",\"license_terms\":\"Access for free at https:\/\/openstax.org\/books\/biology-2e\/pages\/1-introduction\"}]","CANDELA_OUTCOMES_GUID":"52b7e426-b073-47a2-8566-be8f868f8685, a3cb1e40-030c-4689-a374-b8210c518eee","pb_show_title":"on","pb_short_title":"","pb_subtitle":"","pb_authors":[],"pb_section_license":""},"chapter-type":[],"contributor":[],"license":[],"class_list":["post-4322","chapter","type-chapter","status-publish","hentry"],"part":4294,"_links":{"self":[{"href":"https:\/\/courses.lumenlearning.com\/wm-biology2\/wp-json\/pressbooks\/v2\/chapters\/4322","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/courses.lumenlearning.com\/wm-biology2\/wp-json\/pressbooks\/v2\/chapters"}],"about":[{"href":"https:\/\/courses.lumenlearning.com\/wm-biology2\/wp-json\/wp\/v2\/types\/chapter"}],"author":[{"embeddable":true,"href":"https:\/\/courses.lumenlearning.com\/wm-biology2\/wp-json\/wp\/v2\/users\/17"}],"version-history":[{"count":8,"href":"https:\/\/courses.lumenlearning.com\/wm-biology2\/wp-json\/pressbooks\/v2\/chapters\/4322\/revisions"}],"predecessor-version":[{"id":8650,"href":"https:\/\/courses.lumenlearning.com\/wm-biology2\/wp-json\/pressbooks\/v2\/chapters\/4322\/revisions\/8650"}],"part":[{"href":"https:\/\/courses.lumenlearning.com\/wm-biology2\/wp-json\/pressbooks\/v2\/parts\/4294"}],"metadata":[{"href":"https:\/\/courses.lumenlearning.com\/wm-biology2\/wp-json\/pressbooks\/v2\/chapters\/4322\/metadata\/"}],"wp:attachment":[{"href":"https:\/\/courses.lumenlearning.com\/wm-biology2\/wp-json\/wp\/v2\/media?parent=4322"}],"wp:term":[{"taxonomy":"chapter-type","embeddable":true,"href":"https:\/\/courses.lumenlearning.com\/wm-biology2\/wp-json\/pressbooks\/v2\/chapter-type?post=4322"},{"taxonomy":"contributor","embeddable":true,"href":"https:\/\/courses.lumenlearning.com\/wm-biology2\/wp-json\/wp\/v2\/contributor?post=4322"},{"taxonomy":"license","embeddable":true,"href":"https:\/\/courses.lumenlearning.com\/wm-biology2\/wp-json\/wp\/v2\/license?post=4322"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}