Helper T Cells: TH1 cells, TH2 cells, TH17 cells, TFH cells and Treg cells (FL-Immuno/32)

[Music] helper t-cells we now know that activated cd4 positive T cells become helper T cells these cells are termed helper because they help other cells of the immune system to eliminate the pathogens these helper T cells further consists of many subsets in this video lecture we will discuss five main subsets of helper T cells these helper T subsets differ from each other in cytokines that induce their differentiation master transcriptional regulator which regulates the expression of cytokines produced by a particular t-cell subset and cytokines they produce and secrete before moving further let us answer this question of helper T cells are needed by our immune system our body encounters diverse types of infections and infectious agents or pathogens these pathogens varies according to the sites in the body that they invade the cells that they target etc for example some pathogens such as mycobacteria are ingested by the phagocytes but they resist intracellular killing on the other hand parasites such as helminths are too large and cannot be phagocytosed so each of these pathogen is eliminated by a different form of immune response helper t-cells aim to fight against such diverse type of pathogens effectively helper T cells works by secreting cytokines which communicate with the other cells of the immune system and activate them to eliminate the pathogens by appropriate immune response let's now study details of the t-helper subsets t-helper type 1 cells when there is an intracellular infection such as viral or intracellular bacterial infection the dendritic cells in the macrophages secrete interleukin 12 the dendritic cell migrates from the site of infection to a nearby lymph node where it presents the antigen to naive cd4 positive T cell once antigen is recognized the interleukin 12 induces or signals this T cell to become T helper type 1 cell this T helper type 1 cell now starts secreting interferon gamma interferon gamma activates the macrophages and enhances their microbicides activity to kill ingested bacteria this interferon gamma also stimulates the production of antibodies that promote phagocytosis of microbes since these antibodies act as complement proteins recall that complement proteins enhances phagocytosis by a process known as opsonization besides interferon gamma these T helper type 1 cells also produce inter look into which promotes growth and differentiation of other T cells so here we saw that inter look in 12 induces differentiation of T helper type 1 cells and these T cells secrete interferon gamma and inter look into the main function of T helper type 1 cells is to help macrophages to fight against intracellular infections t-helper type 2 sells when there is an infection by parasites such as helminthic parasites the cells of the innate immunity release inter looking for the naive t-cell recognizes the antigen presented by the dendritic cell and in the presence of interleukin 4 this naive T cell differentiates into T helper type 2 cell this cell now starts secreting inter looking for interleukin 5 and Inter look in 13 inter looking for stimulates B cells to produce IgE antibodies interleukin 5 activates mast cells and eosinophils interleukin 13 stimulates the production of mucus and the intestines we know that size of these parasites is too much and they cannot be phagocytosed now let's have a look how these cytokines contribute to the elimination of these parasites the IgE antibodies bind to the surface of parasites or in other words they coat the parasite surface mast cells and eosinophils have receptors for FC region of these antibodies so they bind to the FC region of the antibodies bound to the surface of parasite these parasites are killed by granule enzymes secreted by mast cells and eosinophils the role of mucus secreted is to promote expulsion of parasites from the gut so here we saw that differentiation of T helper type two cells is stimulated by inter looking for and they secrete inter look in four five and thirteen the main role of T helper type two cells is to stimulate immunity against parasites which is mediated by eosinophils and mast cells t helper 17 cells the designation one and two in T helper type one end T helper type two cells respectively were assigned because these were first cd4 positive T cell subsets to be distinguished but T helper 17 cells are so named because the signature cytokine they produces interleukin 17 besides interleukin 17 they also produce inter look in 22 when there is an infection by fungi or by extracellular bacteria interleukin 6 and transforming growth factor beta are produced by cells of innate immunity the naive T cells recognize the antigens of fungi and extracellular bacteria presented by dendritic cell cytokines interleukin 6 and transforming growth factor beta induced this T cell to differentiate into T helper 17 cells interleukin 17 secreted by these cells recruit leukocytes specifically neutrophils to the site of infection they induce inflammation these neutrophils help defend against these extracellular fungi and bacteria it has been found that patients having defective gene for interleukin 17 are more susceptible to bacterial and fungal infections interleukin 17 and Inter look in 22 also help in activating epithelial cells to produce antimicrobial peptides that resist microbial invasion thus we saw that differentiation of T helper 17 subsets is induced by interleukin 6 and transforming growth factor beta T helper 17 cells secrete interleukin 17 and interlock in 22 their main function is to help in fighting against fungal and extracellular bacterial infections the remaining two subsets of helper t-cells are recently discovered here we will talk about their main functions only regulatory t-cells formerly these cells were known as suppressor T cells once a pathogen or infection is eradicated or made harmless by the immune system regulatory t-cells limit the tissue damage caused by the immune response they are so called because of their function to suppress t-cell responses and limiting the immune response thus they are involved in preventing autoimmunity regulatory t-cells communicate with other cells of the immune system and help them to stop their effector functions regulatory t-cells produce transforming growth factor beta and interleukin 10 which help to inhibit inflammation and the immune response interleukin 10 is a potent suppressor of macrophage function transforming growth factor beta induces production of more regulatory t-cells so regulatory t-cells play important role in regulation of immune responses follicular helper t-cells follicular helper T cells secrete interleukin 21 which guide B cells to make suitable antibodies for clearing and infection thus like T helper type 2 cells these follicular T helper cells help b-cells in eradicating infections [Music] [Music]

Channel: Frank Lectures

Views: 197,263

Keywords: Helper T cells, Helper T cell subsets, Type of helper T cells, TH1 cells, TH2 cells, TH17 cells, TFH CELLS, Treg cells, helper T cells animation, role and function of helper T cells, regulatory t cells, follicular helper t cells

Id: Qs1H5P0SaLU

Length: 10min 47sec (647 seconds)

Published: Thu May 25 2017