{"id":211087,"date":"2025-05-03T01:19:26","date_gmt":"2025-05-03T01:19:26","guid":{"rendered":"https:\/\/learnexams.com\/blog\/?p=211087"},"modified":"2025-05-03T09:10:53","modified_gmt":"2025-05-03T09:10:53","slug":"which-is-incorrect-about-the-fc-region-of-an-immunoglobulin-2","status":"publish","type":"post","link":"https:\/\/www.learnexams.com\/blog\/2025\/05\/03\/which-is-incorrect-about-the-fc-region-of-an-immunoglobulin-2\/","title":{"rendered":"Which is incorrect about the Fc region of an immunoglobulin"},"content":{"rendered":"\n

Which is incorrect about the Fc region of an immunoglobulin?<\/p>\n\n\n\n

It forms the antigen binding sites.<\/p>\n\n\n\n

It contains an effector molecule that can bind to cells such as macrophages and mast cells.<\/p>\n\n\n\n

It contains an effector molecule that can fix complement.<\/p>\n\n\n\n

It determines the class to which the immunoglobulin belongs.<\/p>\n\n\n\n

It is called the crystallizable fragment.<\/p>\n\n\n\n

The Correct Answer and Explanation is<\/mark><\/strong>:<\/p>\n\n\n\n

Correct Answer:<\/strong>
It forms the antigen binding sites.<\/strong><\/p>\n\n\n\n

The immunoglobulin (Ig), or antibody, is a Y-shaped glycoprotein molecule produced by B cells as part of the adaptive immune response. It consists of two major functional regions: the Fab (Fragment antigen-binding)<\/strong> region and the Fc (Fragment crystallizable)<\/strong> region. Understanding the distinction between these regions is critical to appreciating how antibodies recognize antigens and recruit other components of the immune system.<\/p>\n\n\n\n

The Fab region<\/strong> is located at the tips of the “Y” arms and is responsible for antigen binding<\/strong>. It contains variable regions<\/strong> of both the heavy and light chains. These variable domains form the paratope<\/strong>, the part of the antibody that specifically binds to an epitope<\/strong> on the antigen. Because these regions are highly variable between different antibodies, they provide the diversity needed to recognize a wide array of antigens.<\/p>\n\n\n\n

In contrast, the Fc region<\/strong> is located at the stem of the “Y” and does not bind antigens<\/strong>. Instead, it is involved in effector functions<\/strong> once the antibody has bound to an antigen through the Fab region. The Fc region is constant (hence \u201cC\u201d for \u201cconstant\u201d) within each class of immunoglobulin and plays several important roles:<\/p>\n\n\n\n

    \n
  1. Effector Molecule Binding<\/strong>: The Fc region can bind to Fc receptors<\/strong> on immune cells such as macrophages<\/strong>, natural killer (NK) cells<\/strong>, mast cells<\/strong>, and neutrophils<\/strong>, facilitating processes like phagocytosis<\/strong> and antibody-dependent cellular cytotoxicity (ADCC)<\/strong>.<\/li>\n\n\n\n
  2. Complement Activation<\/strong>: Certain antibody classes (especially IgG<\/strong> and IgM<\/strong>) can activate the complement system<\/strong> via their Fc regions, which helps destroy pathogens.<\/li>\n\n\n\n
  3. Class Determination<\/strong>: The structure of the Fc region determines the class (isotype)<\/strong> of the immunoglobulin\u2014such as IgA, IgG, IgM, IgE,<\/strong> or IgD<\/strong>\u2014which in turn dictates its distribution and role in the immune system.<\/li>\n\n\n\n
  4. Crystallizable<\/strong>: The Fc portion was so named because it was the fragment that could be crystallized during early biochemical studies.<\/li>\n<\/ol>\n\n\n\n

    Thus, the incorrect statement is that the Fc region “forms the antigen binding sites,” as this function is carried out exclusively by the Fab region<\/strong>.<\/p>\n","protected":false},"excerpt":{"rendered":"

    Which is incorrect about the Fc region of an immunoglobulin? It forms the antigen binding sites. It contains an effector molecule that can bind to cells such as macrophages and mast cells. It contains an effector molecule that can fix complement. It determines the class to which the immunoglobulin belongs. It is called the crystallizable […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"site-sidebar-layout":"default","site-content-layout":"","ast-site-content-layout":"default","site-content-style":"default","site-sidebar-style":"default","ast-global-header-display":"","ast-banner-title-visibility":"","ast-main-header-display":"","ast-hfb-above-header-display":"","ast-hfb-below-header-display":"","ast-hfb-mobile-header-display":"","site-post-title":"","ast-breadcrumbs-content":"","ast-featured-img":"","footer-sml-layout":"","ast-disable-related-posts":"","theme-transparent-header-meta":"","adv-header-id-meta":"","stick-header-meta":"","header-above-stick-meta":"","header-main-stick-meta":"","header-below-stick-meta":"","astra-migrate-meta-layouts":"default","ast-page-background-enabled":"default","ast-page-background-meta":{"desktop":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"tablet":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"mobile":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""}},"ast-content-background-meta":{"desktop":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"tablet":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"mobile":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""}},"footnotes":""},"categories":[25],"tags":[],"class_list":["post-211087","post","type-post","status-publish","format-standard","hentry","category-exams-certification"],"_links":{"self":[{"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/posts\/211087","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/comments?post=211087"}],"version-history":[{"count":0,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/posts\/211087\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/media?parent=211087"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/categories?post=211087"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/tags?post=211087"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}