T Cell Function Flashcards
How are T cells contributing to the pathogenesis of periodontitis?
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What are the two types of cell-mediated immunity?
- CD4 helper T cells produce cytokines that activate and recruit other cells
- CD8 cytotoxic T cells kill infected cells with microbes in cytoplasm
Th1 cells
S subset of CD4 T cells; initiate inflammation and immunity by activating macrophages by secreting interferon gamma
Th17 cell
A subset of CD4 T cells that are characterized by production of the cytokine IL-17. They help recruit neutrophils to sites of infection.
describe the discovery of cell-mediated immunity
- Experiment showing transferable from immune animals to naive animals by T cells but not serum
- bacteria were killed in vitro by activated macrophages not T cells
How do helper T cells develop and mediate their function? (overview)
Different cytokines are involved
How is the recognition of antigen by T cell receptor very specific?
T cell clones express TCR that can only recognize one peptide/MHC complex
Though TCR are very specific, presentation of antigen to T cells by APCs is very ___
diverse
How is the presentation of antigen to T cells by APC very diverse?
- several peptides can be presented by different MHC I and MHC II molecules on the surface of the same dendritic cell
- T cells patrol LN in search of DC with the perfect fit
Give the characteristics of CD4 helper T cell subsets
Th1: make IFNgamma and activate macrophages. This targets intracellular pathogens.
Th2: make IL4, IL5, and IL13 and activate eosinophils. This targets parasites (helminths) through IgE
Th17: make IL17 and IL22 and activate neutrophils. This targets extracellular pathogens.
describe the development of T helper effector cells
- different cytokines are produced by DC or other innate cells that have recognized different types of microbes
- the cytokines induce different transcription factors
- transcription factors determine the fate of the helper T cells
development of Th1 cell
- intracellular microbe discovered
- dendritic cell releases IL-12 cytokine, NK cell releases IFN-gamma cytokine
- T cell now antigen-activated and expresses transcription factors T-bet, STAT4, and STAT1
- Th1 cell formed
development of Th2 cell
- helminth (parasite) discovered
- dendritic cell and mast cells and eosinophils involved, release cytokine IL-4
- T cell now antigen-activated and expresses transcription factors GATA-3 and STAT6
- Th2 cell formed
development of Th17 cell
- extracellular fungi or bacteria discovered
- dendritic cell involved, releases cytokines IL-1, IL-6, IL-23, and TGF-beta
- T cell now antigen activated and expresses transcription factors ROR-gt and STAT3
- Th17 cell formed
Function of Th1 cells
Secrete IGNgamma to induce macrophages to kill ingested microbes in classical macrophage activation (enhanced microbial killing)
how are macrophages activated by Th1 cells?
- involves CD40L (on CD4 cell) and CD40 (expressed on APCs - macrophage, dendritic cell, B cells)
- involves IFNgamma secreted by CD4 cell and IFNgamma receptor
- macrophages produce cytokines, up-regulate MHC, costimulatory molecules, and microbicidal activities
what is the response of macrophage activated by Th1 cells?
- secretion of cytokines TNF, IL-1, IL-12, chemokines
- increased expression of MHC and costimulators (B7 molecules)
- killing of phagocytosed bacteria
Function of Th2 cells
- IL4 induces B cells to produce IgE
- IL5 induces eosinophil activation
- mediates worm elimination, mast cell degranulation, intestinal mucus secretion and peristalsis, and alternative macrophage activation (enhance fibrosis/tissue repair)
compare classical and alternative macrophage activation
M1: killing (by ROS, NO, and lysosomal enzymes) and inflammation
M2: tissue repair and inhibit inflammation (happens at end of immune response)
what triggers a monocyte to differentiate into an M2?
IL-13 and IL-4
what triggers a monocyte to differentiate into an M1?
Microbial TLR-ligans, IFNgamma
Functions of TH17 cells
- IL17 mediate recruitment of neutrophil via induction of cytokines/chemokines production from other cells
- IL22 mediates antimicrobial peptides and increased barrier integrity through epithelial cells
- important for extracellular microbes
functions of Tfh cells
- found in the B cell zone
- make IL21 which mediates production of Ig (immunoglobulin) by B cells
How do cytotoxic T cells mediate their function? (overview)
Recognition of antigens and killing via perforin and granzyme FasL
