Cell Mediated Immunity Flashcards
what percent of peripheral blood T cells are CD4+
- 65%
function of T helper lymphocytes
- secrete cytokines
- induces activation of B-lymphocytes and other cells
function of regulatory T cells
- suppress T lymphocyte proliferation toward the end of an immune reaction
- suppress auto reactive T cells that have escaped negative selection
what percent of peripheral blood T cells are CD8?
- 35%
function of CTLs
- release cytolytic substances such as perforin, granzyme, and ligands directly into target cells
- promotes apoptotic cell death
- virally infected cells and tumor cells
memory T cells
- antigen-specific T cells that persist long-term after an infection has resolved
memory T cells upon re-exposure to cognate antigen
- quickly expand to a large number of effector T cells
memory cell types
- CD4 or CD8
stages of t lymphocyte maturation
- stem cell
- Pro-T
- Pre-T
- Double Positive
- Single positive immature
- naive mature
thymocytes that originate from the bone marrow
- lack expression of the T cell receptor
double negative thymocytes
- do not express CD4 or CD8
- up regulate expression of cell surface glycoproteins followed by TCR gene arrangement
where does maturation of T cells occur?
- in the thymus
two processed of thymic education
- MHC restriction
- self tolerance
MHC restriction
- CORTICAL thymic epithelial cells asks developing T-cells if it recognizes the self MHC molecule it is expression
- correct answer is yes
- positive selection
positive selection and affinity
- want low to moderate affinity
cells that connect bind and recognize self-MHC or bind with too low an affinity
- undergo apoptosis
self tolerance
- MEDULLA thymic epithelial cells asks developing T cells if it recognizes self peptides on MHC molecules
- correct answer is no
- negative selection
negative selection and affinity
- thymocytes that bind self peptides with high affinity
- deletes possible auto-reactive T cells
naive T cells
- single positive thymocytes that leave in a resting phenotype
activation of naive T cells
- single positive T cells
- go from lymph node to blood seeking encounters with pathogen
- TCR binds target peptide
- receives signal to become activated cell
MHC class I displays
- fragments of proteins from pathogens inside cell
MHC class II displays
- fragments of proteins from pathogens living outside a cell
signal 1 of T cell activation
- TCR binding a peptide
signal 2 of T cell activation
- CD28 binding to B7
in absence of costimulatory signal
- T cells become anergized
- no longer responsive to antigen stimulation
how costimulation works
- CD28 binds to B7
- protein kinases phosphorylate ITAMS on CD3 proteins
- signal transduction
cytokine that T cell proliferation is dependent on
IL-2
initiation and expression of IL-2 requires
- signals delivered by TCR:MHC coreceptor complex
- and CD28
IL-2 functions in what kind of manner?
- autocrine
how IL-2 promotes cell division and clonal expanstion
- binds to CD25 receptor upregulated by activated T cells
effector functions of CD4+ T cells in cell-mediated immunity
- activate macrophages for killing of phagocytosed microbes
- CD40-40L
- interferon gamma
effector functions of CD4+ T cells in humoral immunity
- bind to B-lymphocyte
- CD40-40L
- secretion of antibodies with enhanced abilities to neutralize and eliminate antigens
host defense of TH1
- intracellular microbes
host defense of TH2
- helminthic parasites
host defense of TH17
- extracellular bacteria, fungi
initiating cytokine to produce TH1
- IL-12
- IFN-gamma
initiating cytokine to produce TH2
- IL-4
initiating cytokine to produce TH17
- IL-6
- IL-23
- TGF-Beta
CD4 T cell proliferation cytokine
- IL-2
cytokines secreted by TH1
- IFN-gamma
- TNF-alpha
- proinflammatory
cytokines secreted by TH2
- IL-4
- IL-5
- IL-13
cytokines secreted by TH17
- IL-17A/F
- IL-22
function of interferon-gama
- stimulates macrophages to ingest extracellular bacteria and viruses
- induces IgG2a and IgG3 class switching by B cells
- blocks differentiation of TH2 cells
IgG2a and IgG3 class switching by B cells function
promotes opsonization
source of IL-4
- basophils
function of IL-4
- promotes B cell proliferation
- enhances IgE class switching
- recruits eosinophils
- blocks differentiation of TH1 cells
function of IL-5
- elicits B cell growth
- activates eosinophils
- enhances IgE production
function of IL-17
- stimulation of inflammation
- increased barrier function
how CD4+ T cells helps CD8+ T cells
- produce cytokines that stimulate CTL differentiation
- enhance ability to APCs to stimulate CTL differentiation
CD8+ cytotoxic T cell effector mechanisms
- antigen recognition and binding of CTL to target cell
- CTL activation and granule exocytosis
- apoptosis of target cell
aberrantly high level of T cell activation associated with
- autoimmune disease
- SLE
aberrantly low level of CD4 T cells problem in
- HIV/AIDS
success of organ transplant due to
- suppression of T cell activation
T cell activation by bacterial toxin can lead to
- massive T cell responses
- TSS, food poisoning, etc
immunotherapy of cancer highly dependent on
- T cell activation
strategy of immunosuppression relied heavily on
- blocking T cell activation
