T-Cell Immunity I Flashcards
When are T cells functionally mature?
Functional T cells are essential for defending against various pathogens.
Naïve T cells that egress the thymus, termed recent thymic emigrant (RTE), are not functionally mature and required to home to peripheral tissues and secondary lymphoid
organs for further maturation.
Define native T cells.
When is adaptive immune response initiated?
Naïve T cells: Mature, recirculating T cells that have not yet encounter their known
antigens
Adaptive immune response is initiated when naïve T cells recognize peptide-MHC complex on the surface of antigen presenting cells (APCs); upon TCR signaling, T cells are “activated”
What does successful interaction with APCs result in?
The successful interaction with APCs results in the generation of effector T cells
What do T cells act on? Pathogens or target cells?
Effector T cells then act on target cells, not the pathogens themselves
Compare Naive vs memory T cells.
How can they be identified? Give specifics.
Naive : CD45RA
Memory CD45RO
Effector memory: rapidly mature into effector cells upon reactivation and
enter inflamed tissues
Central memory: take longer than effector T cells in producing cytokines;
remain in lymphoid tissue and circulate as naïve T cells
Memory T cells are long-lived
Describe the recognition of antigenic peptide and T cell activation.
What three signals are required for successful T cell activation?
- TCR recognizes peptide in context of self MHC
- Engaging of co-stimulatory molecules: CD28 with CD80/86; CD40L with CD40
- Inducing cytokine expression and secretion; a combination of specific cytokines
dictates the generation of functionally different T cell responses and T cell fates - Activated T cells express high affinity IL2Rα (CD25) and proliferate in responding to
IL2 in an autocrine fashion.
A combination of specific transcription factors and cytokines drives functional differentiation of CD4 T cells.
For the type of effector T cell give its main functions and pathogens targeted:
- CD8 cytotoxic T cells
- CD4 Th1 cells
- CD4 Th2 cells
- CD Th17 cells
- TFH cells
- CD4 regulatory T cells (various types
See chart p 3
- CD8 cytotoxic T cells: kills virus infected cells (targest viruses some intracellular bacteria)
- CD4 Th1 cells: activate infected macrophages, provide help to B cells for antibody production (targets microbes that persist in macrophage vescicles, extracellular bacteria)
- CD4 Th2 cells: provides help to B cells for antibody production, especially switching to IgE (targest Helminth parasites)
- CD Th17 cells: enhance neutrophil response, promote barrier integrity like skin, intestine (targets fungi)
- TFH cells: B-cell help isotype switching antibody production (targets all types)
- CD4 regulatory T cells (various types): suppress T-cell responses
Draw a diagram that shows the forms a Naive CD4 can become. Include their interleukins.
p 3
becomes:
Th1, Th2, Th17, Thf, iTreg
Effector CD4pos T cells can be classified by cytokines they produce. Cytokines are communicators amongst leukocytes – the interleukins.
Describe Type I Immune response: (What type of T cells? What IL? What targets?)
- Type I immune response: T Helper 1 or Th1
- Th1: IFNγ, IL2, Lymphotoxin-α (LTα)
- Intracellular pathogens
- Various autoimmune diseases: self antigens, e.g. diabetes
Effector CD4pos T cells can be classified by cytokines they produce. Cytokines are communicators amongst leukocytes – the interleukins.
Describe Type II Immune response: (What type of T cells? What IL? What targets?)
Type II immune response: T Helper 2 or Th2
- Th2: IL4, IL5, IL13
- Extracellular pathogens
- Immunopathology of allergy, asthma, dermatitis
Effector CD4pos T cells can be classified by cytokines they produce. Cytokines are communicators amongst leukocytes – the interleukins.
Describe iTreg Cells Immune response: ( What IL? What targets?)
iTreg Cells:
- TGF beta, IL10
- Immune tolerance, regulation of immune response to self antigens
Effector CD4pos T cells can be classified by cytokines they produce. Cytokines are communicators amongst leukocytes – the interleukins.
Describe Th17 Cells Immune response: ( What IL? What targets?)
Th17 Cells
- Th17: IL17, IL21, IL22
- gut immunity (Th1)
Effector CD4pos T cells can be classified by cytokines they produce. Cytokines are communicators amongst leukocytes – the interleukins.
Describe T follicular helper Cells (Thf) Immune response.
T follicular helper cells (Thf)
- Thf: IL6, IL10, IL21; B cells to form germinal center, differentiation of B cells
into memory B cells, plasma cells (Th2)
What can initiate immune response?
Which cells respond?
Dangerous signals, either from an external source like a pathogen, or internal
source like a structurally altered protein
The cells that respond to the dangerous signals are macrophages, dendritic cells
Their unique function is to uptake pathogens, and process bacterial proteins for antigen presentation in the context of self MHC moleculules
- They can also respond to soluble bacterial products and viral RNA, DNA through the Toll-like receptors (TLRs)
Downstream signaling of TLR is orchestration of multiple cytokine gene expression
Describe toll like receptors and their ligands.
TLRs are present on both cell surface Membrane and membrane of intracellular vesicles
TLRs and their ligands
Ligands are collectively known as Pathogen Associated Molecular Patterns (PAMPs),
Danger Associated Molecular Patterns (DAMPs) or Microbial Associated Molecular
Patterns (MAMPs)
diagram/chart p 5
