Helper T cells | Immune system physiology

Helper T cells:

Are a type of T cell that play an important role in the immune system, particularly in the adaptive immune system. They help the activity of other immune cells by releasing T cell cytokines. These cells help suppress or regulate immune responses. They are essential in B cell antibody class switching, in the activation and growth of cytotoxic T cells, and in maximizing bactericidal activity of phagocytes such as macrophages.

Mature Th cells express the surface protein CD4 and are referred to as CD4+ T cells. Such CD4+ T cells are generally treated as having a pre-defined role as helper T cells within the immune system. For example, when an antigen-presenting cell expresses an antigen on MHC class II, a CD4+ cell will aid those cells through a combination of cell to cell interactions (e.g. CD40 (protein) and CD40L) and through cytokines.

CD154, also called CD40 ligand or CD40L, is a cell surface protein that mediates T cell helper function in a contact-dependent process and is a member 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. 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, CD154 promotes B cell maturation and function by engaging CD40 on the B cell surface and therefore facilitating cell-cell communication. A defect in this gene results in an inability to undergo immunoglobulin class switching and is associated with hyper IgM syndrome. Absence of CD154 also stops the formation of germinal centers and therefore prohibiting antibody affinity maturation, an important process in the adaptive immune system.

The importance of helper T cells can be seen from HIV, a virus that primarily infects CD4+ T cells. In the advanced stages of HIV infection, loss of functional CD4+ T cells leads to the symptomatic stage of infection known as the acquired immunodeficiency syndrome (AIDS). When the HIV virus is detected early in blood or other bodily fluids, continuous therapy can delay the time at which this fall happens. Therapy can also better manage the course of AIDS if and when it occurs. There are other rare disorders such as lymphocytopenia which result in the absence or dysfunction of CD4+ T cells. These disorders produce similar symptoms, many of which are fatal.

 

Resources
Link 1

 


Introduction to helper T cells and their role in activating B cells. Created by Sal Khan.

Watch the next lesson: https://www.khanacademy.org/test-prep/nclex-rn/rn-immune-system/rn-the-immune-system/v/cytotoxic-t-cells?utm_source=YT&utm_medium=Desc&utm_campaign=Nclex-rn

Missed the previous lesson? https://www.khanacademy.org/test-prep/nclex-rn/rn-immune-system/rn-the-immune-system/v/professional-antigen-presenting-cells-apc-and-mhc-ii-complexes?utm_source=YT&utm_medium=Desc&utm_campaign=Nclex-rn

NCLEX-RN on Khan Academy: A collection of questions from content covered on the NCLEX-RN. These questions are available under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License (available at http://creativecommons.org/licenses/by-nc-sa/3.0/us/).

About Khan Academy: Khan Academy offers practice exercises, instructional videos, and a personalized learning dashboard that empower learners to study at their own pace in and outside of the classroom. We tackle math, science, computer programming, history, art history, economics, and more. Our math missions guide learners from kindergarten to calculus using state-of-the-art, adaptive technology that identifies strengths and learning gaps. We’ve also partnered with institutions like NASA, The Museum of Modern Art, The California Academy of Sciences, and MIT to offer specialized content.

For free. For everyone. Forever. #YouCanLearnAnything

Subscribe to Khan Academy’s NCLEX-RN channel: https://www.youtube.com/channel/UCDx5cTeADCvKWgF9x_Qjz3g?sub_confirmation=1
Subscribe to Khan Academy: https://www.youtube.com/subscription_center?add_user=khanacademy

(Visited 72 times, 5 visits today)

Other Videos You Might Like:

0 0 votes
Article Rating
Subscribe
Notify of
guest

This site uses Akismet to reduce spam. Learn how your comment data is processed.

317 Comments
Newest
Oldest Most Voted
Inline Feedbacks
View all comments