{"id":214405,"date":"2025-05-14T09:10:53","date_gmt":"2025-05-14T09:10:53","guid":{"rendered":"https:\/\/learnexams.com\/blog\/?p=214405"},"modified":"2025-05-14T09:10:55","modified_gmt":"2025-05-14T09:10:55","slug":"cytotoxic-t-lymphocyte-negative-selection-thymus-cortex-of-thymus-helper-t-lymphocyte-recognizes-self-antigen-sel-antigen-tcr-mhc-class-positive-selection-cds-cd4-thymic-epithelial-cell-presents-m","status":"publish","type":"post","link":"https:\/\/www.learnexams.com\/blog\/2025\/05\/14\/cytotoxic-t-lymphocyte-negative-selection-thymus-cortex-of-thymus-helper-t-lymphocyte-recognizes-self-antigen-sel-antigen-tcr-mhc-class-positive-selection-cds-cd4-thymic-epithelial-cell-presents-m\/","title":{"rendered":"Cytotoxic T- lymphocyte Negative selection Thymus Cortex of thymus Helper T- lymphocyte Recognizes self- antigen Sel antigen TCR MHC class Positive selection -CDs CD4 Thymic epithelial cell presents MHC Dendritic cell presents self antigen Thymocyte Binds to MHC molecule"},"content":{"rendered":"\n<p class=\"wp-block-paragraph\"> Cytotoxic T- lymphocyte Negative selection Thymus Cortex of thymus Helper T- lymphocyte Recognizes self- antigen Sel antigen TCR MHC class Positive selection -CDs CD4 Thymic epithelial cell presents MHC Dendritic cell presents self antigen Thymocyte Binds to MHC molecule? No Destroyed by apoptosis No Survives 2% of cells survive selection process in the thymus Selective loss of either CD4 or CD8 proteins T lymphocytes retain only CD4 protein Retains only CD8 protein<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong><mark style=\"background-color:rgba(0, 0, 0, 0)\" class=\"has-inline-color has-ast-global-color-1-color\">The Correct Answer And Explanation is:<\/mark><\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\">To properly label the figure described in your request, we need to understand the <strong>T-cell maturation and selection process<\/strong> in the <strong>thymus<\/strong>, where immature <strong>thymocytes<\/strong> develop into functional <strong>T lymphocytes<\/strong>. Here\u2019s how the elements you listed fit into the flow and labeling:<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h3 class=\"wp-block-heading\"><strong>Correct Labeling (based on the process):<\/strong><\/h3>\n\n\n\n<ol class=\"wp-block-list\">\n<li><strong>Thymus<\/strong> \u2013 The organ where T-cell maturation occurs.<\/li>\n\n\n\n<li><strong>Cortex of thymus<\/strong> \u2013 Site of <strong>positive selection<\/strong>.<\/li>\n\n\n\n<li><strong>Thymocyte<\/strong> \u2013 Immature T cell.<\/li>\n\n\n\n<li><strong>TCR (T-cell receptor)<\/strong> \u2013 Present on thymocytes to recognize antigens.<\/li>\n\n\n\n<li><strong>MHC class I and II molecules<\/strong> \u2013 Presented by <strong>thymic epithelial cells<\/strong> (for positive selection).<\/li>\n\n\n\n<li><strong>Thymic epithelial cell presents MHC<\/strong> \u2013 In cortex, presenting self-MHC to thymocytes.<\/li>\n\n\n\n<li><strong>Binds to MHC molecule?<\/strong><\/li>\n<\/ol>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Yes \u2192 Survives<\/strong><\/li>\n\n\n\n<li><strong>No \u2192 Destroyed by apoptosis<\/strong><\/li>\n<\/ul>\n\n\n\n<ol class=\"wp-block-list\">\n<li><strong>Positive selection<\/strong> \u2013 Occurs in the cortex, ensures thymocytes can recognize self-MHC.<\/li>\n\n\n\n<li><strong>Selective loss of either CD4 or CD8 proteins<\/strong> \u2013 Based on MHC recognition.<\/li>\n<\/ol>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>MHC Class I \u2192 Retains CD8 \u2192 Cytotoxic T-lymphocyte<\/strong><\/li>\n\n\n\n<li><strong>MHC Class II \u2192 Retains CD4 \u2192 Helper T-lymphocyte<\/strong><\/li>\n<\/ul>\n\n\n\n<ol class=\"wp-block-list\">\n<li><strong>Medulla of thymus<\/strong> \u2013 Site of <strong>negative selection<\/strong>.<\/li>\n\n\n\n<li><strong>Dendritic cell presents self-antigen<\/strong> \u2013 In medulla.<\/li>\n\n\n\n<li><strong>Recognizes self-antigen?<\/strong>\n<ul class=\"wp-block-list\">\n<li><strong>Yes \u2192 Destroyed by apoptosis<\/strong><\/li>\n\n\n\n<li><strong>No \u2192 Survives<\/strong><\/li>\n<\/ul>\n<\/li>\n\n\n\n<li><strong>Negative selection<\/strong> \u2013 Removes self-reactive T cells.<\/li>\n\n\n\n<li><strong>2% of cells survive selection process in the thymus<\/strong> \u2013 Final surviving mature T cells.<\/li>\n<\/ol>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h3 class=\"wp-block-heading\"><strong>300-Word Explanation:<\/strong><\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">T-cell maturation is a critical immunological process occurring in the <strong>thymus<\/strong>, ensuring the development of functional but non-self-reactive <strong>T lymphocytes<\/strong>. Immature T cells, or <strong>thymocytes<\/strong>, enter the <strong>cortex<\/strong> of the thymus where they undergo <strong>positive selection<\/strong>. This stage tests whether thymocytes can recognize <strong>self-MHC molecules<\/strong> using their <strong>T-cell receptor (TCR)<\/strong>. If the thymocyte <strong>fails to bind MHC<\/strong>, it undergoes <strong>apoptosis<\/strong>. If it binds appropriately, it survives and progresses.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">After passing positive selection, thymocytes undergo <strong>lineage commitment<\/strong>:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>If a thymocyte binds to <strong>MHC class I<\/strong>, it downregulates CD4 and retains <strong>CD8<\/strong>, becoming a <strong>cytotoxic T lymphocyte<\/strong>.<\/li>\n\n\n\n<li>If it binds <strong>MHC class II<\/strong>, it retains <strong>CD4<\/strong>, becoming a <strong>helper T lymphocyte<\/strong>.<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">Next, in the <strong>medulla<\/strong>, <strong>negative selection<\/strong> occurs. Here, <strong>dendritic cells<\/strong> and <strong>medullary thymic epithelial cells<\/strong> present various <strong>self-antigens<\/strong>. Thymocytes that <strong>strongly recognize self-antigens<\/strong> are eliminated via apoptosis, preventing <strong>autoimmunity<\/strong>.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">This two-step selection process is highly stringent; <strong>only about 2%<\/strong> of all thymocytes survive both tests. These surviving T cells exit the thymus as mature, <strong>self-MHC-restricted<\/strong> and <strong>self-tolerant<\/strong> lymphocytes. This mechanism ensures a competent and safe adaptive immune response, crucial for defending the body against pathogens while preventing attacks on self-tissues.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">In summary, labeling the figure with the correct terms reflects the tightly regulated development of T cells through positive and negative selection in the thymus, forming the foundation of adaptive immunity.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Cytotoxic T- lymphocyte Negative selection Thymus Cortex of thymus Helper T- lymphocyte Recognizes self- antigen Sel antigen TCR MHC class Positive selection -CDs CD4 Thymic epithelial cell presents MHC Dendritic cell presents self antigen Thymocyte Binds to MHC molecule? No Destroyed by apoptosis No Survives 2% of cells survive selection process in the thymus Selective [&hellip;]<\/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-214405","post","type-post","status-publish","format-standard","hentry","category-exams-certification"],"_links":{"self":[{"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/posts\/214405","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=214405"}],"version-history":[{"count":0,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/posts\/214405\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/media?parent=214405"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/categories?post=214405"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/tags?post=214405"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}