CD4 T cells: The Master Controllers of the Immune System

Ifeoma Ezepue
Flashcards by Ifeoma Ezepue, updated more than 1 year ago
Ifeoma Ezepue
Created by Ifeoma Ezepue about 4 years ago


University Fundamentals of Medicine (Immunology) Flashcards on CD4 T cells: The Master Controllers of the Immune System, created by Ifeoma Ezepue on 11/10/2015.

Resource summary

Question Answer
Where do T cells develop? thymus
What are the two types of T cells? Conventional and Unconventional
What are the subcategories of conventional T cells? T helper cells CD4+ Cytotoxic T cells CD8+
What are the subcategories on unconventional T cells? yd cells -good at fighting carcinomas intraepithelial lymphocytes (IELS) -go to epithelial layers of body e.g. gut/lung -good at fighting carcinomas (tumours with epi origin) NKT cell -T cells with NK properties
What is the importance of CD4+ T cells in HIV? they are progressively lost in HIV infection infected, strong flu few weeks later virus level peaks and dip in CD4 as CD4 target virus levels drop a bit - clinical latency virus resurfaces CD8 killing infected CD4 CD4 reaches v. low immunodeficiency AIDS - opportunistic infections problem
How do T cells recognise antigens? using a T cell receptor ^this is the definition of a T cell
What distinguishes CD4 T cells from other cells? has 60-70 thousand CD4 molecules on surface
Describe the autocrine growth pathway T cell recognises correct peptide plus MHC activates CD4 T cell starts expressing receptor for cytokine IL-2 (CD25) starts producing IL-2 - growth factor that acts upon itself in an autocrine fashion produces alpha subunit of IL-2 receptor so has a receptor that can bind with IL-2
What do activated CD4+ Th cells do?di differentiate into eitherTh0 or Th1 or Th2 (Th0 secretes IL-2, IL-4 and INF-y then differentiate into Th1 or Th2)
What do Th1 cells produce and which immune response do they control? IFN-y TNFa TNFb IL-2 IL-3 cell-mediated immunity
What do Th2 cells produce and which immune response do they (control? IL-4 IL-5 IL-13 humoral immunity (immunity of fluids)
Out of cell-mediated and humoral immunity which one deals with intracellular and which deals with extracellular pathogens? intracellular pathogens (cell mediated) extracellular pathogens (humoral)
What do Th1 cells do? they help macrophages when viruses and bacteria have evolved mechanisms to live inside them Th1 cells come along and secrete IFN-y activates macrophage becomes activated macrophage kills viruses and bacteria
Why don't you make activated macrophages from the start? they cause scarring making substances that damage tissue if not controlled get more tissue damage than the pathogen would have done resulting in immunopathology
Some bacteria are hard to kill such as TB. What happens then? TB-infected activated macrophage Th1 walls off the infected macrophages called caseating granuloma full of macrophages, Th1 and TB but is physically walled off so tissue around it is healthy person won't know they're infected patient is asymptomatic if get rid of Th1, wall breaks down, TB spreads
What does IL-4 induce in B cells? induces b-cells to make IgE
Explain the concept of 'T-cell help' DC sees pathogen, internalizes it and displays protein on MHC-Class II goes to lymph nodes, Th2 made antigen from infected tissue washed down in lymphatic fluid to lymph node B cells in lymph nodes B cells sees antigen, internalizes it and displays protein on MHC-Class II Th2:TCR:protein:MHC-Class II-B cell Th2 release cytokine (IL-4,5,13) stimulates B cell produce plasma cells IgM, IgG, IgE, IgA
How do T cells know to become Th1 or Th2 cells? start off as Th0 cells cytokines turn Th0 into either Th1 or Th2
In what situation will Th0 turn to Th2? Th0 cells differentiate into T2 cells in presence of IL-4 made from mast cells
In what situation does Th0 turn into Th1? Th0 differentiate into Th1 in presence of IL-12 or IL-23
Explain the two manifestations of leprosy? Tuberculoid Th1 is dominate response limited disease cytokines: IFN-y activated macrophages low numbers of organisms Lepromatous Th2 is dominate response disseminated disease Cytokines: IL-4, IL-5, IL-13 hyperglobulinemia high numbers of organisms
Explain the two manifestations of Leishmaniasis Cutaneous/orient boils Th1 is dominant response limited disease Visceral/black fever Th2 is dominant response disseminated response
What are the two manifestations of Tuberculosis? Lepromatous TB Th1 dominant limited disease Miliary TB Th2 dominant disseminated disease
Problem with Th2 response in the west Th2 responses lead to IL-4 which leads to IgE which causes allergies
Give an example of a classical IgE-mediated allergy (Type-I hypersensitivity) Eczema
Th0 differentiates into many different transcription factors, state what they are and which cytokines stimulate the differentiate of Th0 to them T-bet Th1 IL-12, IL-23 GATA-3 Th2 IL-4 RORyt Th17 TGFb,IL-6,IL-21 Foxp3 iT-Reg TGFb
What do Th17 and iT-Reg cells make? former: IL-17, IL-22 latter: TGFb, other suppressive molecules (dampens down immune response)
Th17 and iT-Reg cells defend against?... Th17 - extracellular bacteria (autoimmunity), induce production of neutrophils iT-Reg- immunosuppression (autoimmunity, cancer)
What do a fraction of the activated T and B cells become? memory cells providing long-lasting immunity to that infection -stored for rapid deployment if infection re-occurs
Define the term immunological memory the ability of the immune system to respond quicker and better to pathogens that have been encountered previously
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