CD154: Difference between revisions

Latest revision as of 11:51, 15 February 2025

CD154 and T-dependent B cell activation[edit]

CD154, also known as CD40 ligand, is a crucial protein involved in the immune system's response to antigens. It plays a significant role in T-dependent B cell activation, a process essential for the production of high-affinity antibodies and the establishment of immunological memory.

Structure and Expression[edit]

CD154 is a member of the tumor necrosis factor (TNF) superfamily and is primarily expressed on activated T cells. It is a type II transmembrane protein that interacts with CD40, a receptor found on B cells, dendritic cells, and other antigen-presenting cells.

Mechanism of Action[edit]

The interaction between CD154 and CD40 is pivotal for T-dependent B cell activation. When a helper T cell recognizes an antigen presented by a B cell, CD154 is upregulated on the T cell surface. This upregulation allows CD154 to bind to CD40 on the B cell, delivering a critical signal that promotes B cell proliferation, differentiation, and isotype switching.

Role in B Cell Activation[edit]

T-dependent B cell activation involves several steps:

1. Antigen Recognition: B cells recognize and internalize antigens through their B cell receptor (BCR). 2. Antigen Presentation: The internalized antigen is processed and presented on the B cell surface in association with MHC class II molecules. 3. T Cell Help: Helper T cells recognize the antigen-MHC complex and provide help through CD154-CD40 interaction. 4. B Cell Proliferation and Differentiation: The CD154-CD40 interaction, along with cytokines secreted by T cells, drives B cell proliferation and differentiation into plasma cells and memory B cells.

Clinical Significance[edit]

Defects in CD154 expression or function can lead to immunodeficiency disorders, such as Hyper-IgM syndrome, where patients have an impaired ability to produce certain types of antibodies. Conversely, overexpression of CD154 has been implicated in autoimmune diseases and chronic inflammation.

Related pages[edit]

@@ Line 1: / Line 1: @@
-'''CD154''', also known as '''CD40 ligand''' or '''CD40L''', is a protein that is primarily expressed on activated T cells and is part of the TNF superfamily of molecules. It binds to CD40 on antigen-presenting cells (APC), which leads to many effects depending on the target cell type. In general, CD40L plays the role of a costimulatory molecule and induces activation in APC in association with T cell receptor stimulation by MHC molecules on the APC. In addition to its expression on T cells, CD40L is also found on platelets, mast cells, and basophils.
+== CD154 and T-dependent B cell activation ==
-== Function ==
+[[File:T-dependent_B_cell_activation.png|thumb|right|Diagram of T-dependent B cell activation]]
-CD154 acts as a costimulatory molecule and is particularly important on a subset of T cells called T follicular helper cells (Tfh cells). On Tfh cells, CD40L promotes B cell maturation and function by engaging CD40 on the B cell surface and therefore facilitating cell-cell communication. CD154 expression on Tfh cells is necessary for their development, maintenance, and function.
-== Clinical significance ==
+CD154, also known as CD40 ligand, is a crucial protein involved in the [[immune system]]'s response to antigens. It plays a significant role in T-dependent B cell activation, a process essential for the production of high-affinity [[antibodies]] and the establishment of [[immunological memory]].
-Mutations in this gene result in [[Hyper IgM syndrome]], where its absence prevents the immune system from switching from making antibodies of the IgM type to antibodies of other types. It is also involved in the pathophysiology of many autoimmune diseases (e.g., systemic lupus erythematosus, rheumatoid arthritis).
-== See also ==
+=== Structure and Expression ===
-* [[Cluster of differentiation]]
-* [[CD40 (protein)]]
-* [[Hyper IgM syndrome]]
-== References ==
+CD154 is a member of the [[tumor necrosis factor]] (TNF) superfamily and is primarily expressed on activated [[T cells]]. It is a type II transmembrane protein that interacts with [[CD40]], a receptor found on [[B cells]], [[dendritic cells]], and other antigen-presenting cells.
-<references />
-== External links ==
+=== Mechanism of Action ===
-* [https://www.ncbi.nlm.nih.gov/gene/959 CD154] at the US National Library of Medicine Medical Subject Headings (MeSH)
+The interaction between CD154 and CD40 is pivotal for T-dependent B cell activation. When a [[helper T cell]] recognizes an antigen presented by a B cell, CD154 is upregulated on the T cell surface. This upregulation allows CD154 to bind to CD40 on the B cell, delivering a critical signal that promotes B cell proliferation, differentiation, and [[isotype switching]].
+=== Role in B Cell Activation ===
+T-dependent B cell activation involves several steps:
+. '''Antigen Recognition''': B cells recognize and internalize antigens through their [[B cell receptor]] (BCR).
+. '''Antigen Presentation''': The internalized antigen is processed and presented on the B cell surface in association with [[MHC class II]] molecules.
+. '''T Cell Help''': Helper T cells recognize the antigen-MHC complex and provide help through CD154-CD40 interaction.
+. '''B Cell Proliferation and Differentiation''': The CD154-CD40 interaction, along with cytokines secreted by T cells, drives B cell proliferation and differentiation into [[plasma cells]] and [[memory B cells]].
+=== Clinical Significance ===
+Defects in CD154 expression or function can lead to [[immunodeficiency]] disorders, such as [[Hyper-IgM syndrome]], where patients have an impaired ability to produce certain types of antibodies. Conversely, overexpression of CD154 has been implicated in [[autoimmune diseases]] and [[chronic inflammation]].
+== Related pages ==
+* [[CD40]]
+* [[B cell]]
+* [[T cell]]
+* [[Antibody]]
+* [[Immune system]]
-[[Category:Clusters of differentiation]]
 [[Category:Immunology]]
-[[Category:Proteins]]
-{{Immunology-stub}}