Term
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Definition
| located on APC, recognized by CD28 receptor on naive T cell. Don't express costimulators when its not a threat, APC is secreting cytokines which bind to the t-cell and influence it. |
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Term
| Biggest secretor of cytokines |
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Definition
Adaptive: CD$+ T cells
Innate: dendritic and macrophages |
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Term
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Definition
First cytokine to be produced by CD4+ T cells, activation increases expression of high affinity IL-2 receptor on T cells
- Enhances ability of T cells to bind and respond to IL-2; autocrine cytokine action |
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Term
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Definition
activate phagocytes & B cells to:
- Expressing specific surface molecules (B7)
- Secreting cytokines (IL-12, important for t cell activation) |
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Term
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Definition
Most important cell surface proteins involved in effector functions of CD4+ T cells. Transcribed in CD4+ T cells in response to antigen recognition and costimulation. Expressed on activated helper T cellsl. Binds to CD40 receptor on macrophages, B cells & dendritic cells.
CD40 ligand is on T cell, Binds to CD40 receptor on macrophages, B cells and dendritic cells |
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Term
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Definition
Produce interferon gamma
- activates phagocytes to kill ingested microbes
- stimulates production of antibodies:
Promote ingestion of microbes by phagocytes |
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Term
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Definition
produce cytokines IL-4 & IL-5
* IL-4: stimulates production of IgE antibody by B cells. Helps in activation of mast cells by protein antigens. Coats helminthes
* IL-5: activates eosinophils, destroys helminths |
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Term
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Definition
Induce inflammation; destroys extracellular bacteria and fungi. May contribute to inflammatory diseases; i.e. rheumatoid arthritis.
* Cytokines IL-17 and IL-22; recruit leukocytes to sites of antigen recognition. Without these, people are susceptible to extracellular bacterial infections. |
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Term
| Two types of cell-mediated immune reactions |
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Definition
* Release of cytokines by CD4+ T cells
- recruit and actiavte other leukocytes to destroy microbes.
* Killing of infected cells by CD8+ T cells: eliminates cellular reservoirs of infection, dont need helper t cells, act on their own. |
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Term
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Definition
Two types of migration:
* Between blood and lymphoid tissue until they encounter dendritic cells displaying antigens.
* Back to sites of infections to kill microbes. |
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Term
| Leukocyte migration is controlled by 3 protein families. |
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Definition
Selectins, integrins, chemokines
- Naive and effector T cells express different adhesion molecules |
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Term
| Naive T cells home to lymph nodes |
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Definition
L-selectin and integrins on T cell bind ligands on high endothelial venules (HEV)
- chemokines expressed on HEV bind to receptors on T cells, enhancing integrin binding. |
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Term
| Adhesion molecule expression for effector t cells |
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Definition
Effector T cells home to sites of infection in peripheral tissues.
* Mediated by E-selectin, P-selectin, integrins and chemokines secreted at inflammatory sites |
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Term
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Definition
| really important receptor on lymphocytes, integrate with ligand on endothelium for tight binding. |
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Term
| Role of TH1 cells in host defense |
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Definition
| * Major function is activate macrophages: cd40 lignad - cd40 interactions. secrete cytokine interferon gamma. |
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Term
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Definition
Produce microbicidal substances that kill ingested microbes. Secrete cytokines that induce inflammation: tumor necrosis factor, interleukin-1 and interleukin 12.
Secrete chemokines that recruit leukocytes. Express more MHC molecules and costimulators.
Interferon gamma activates macrophages
IL-12 helps to further activate T cells, ultimately get better macrophages |
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Term
| Innate/Adaptive Interactions |
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Definition
APCs that encounter microbes secrete IL-12;
Stimulates naive CD4+ T cells to differentiate into IFN gamma secreting TH1 cells. This in turn, enhances IFN gamma production, activating macrophages to kill ingested microbes. |
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Term
| Role of TH2 cells in Host Defense |
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Definition
Doesn't stimulate macrophages
- IL-4 production
* stimulates production of IgE antibodies which bind Fc receptors on mast cells and eosinophils
* Production of IL-5
- actiavtes eosinophils
- contain granule proteins that kill helminthic parasites
- cytokines that inhibit classical macrophage activation |
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Term
| Role of TH17 cells in host defense |
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Definition
Induce other cells to secrete cytokines important for recruitment of neutrophils (and monocytes) - leukocytes brought to site of infection
* stimulate production of defensins; anti-microbial substances, function like locally produced antibiotics. Produce cytokines that maintain function of epithelial barriers |
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Term
| Effector Functions of Cytotoxic T cells (CTL) |
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Definition
Kill cells expressing MHC class I-associated peptides.
- recognize peptides
- form tight adhesions
* CTL releases granule contents
- perforins, granzymes, induce apoptosis |
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Term
| Eradication of intracellular infections |
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Definition
Relies on cooperation by CD4 and CD8 T cells
- in some macrophage infected by intracellular bcaterium; some sequestered in vesicles phgaosomes, others escape into cytoplasm
* CD4+ t cells recognize antigesn from vesicular microbes: activate macrophage to kill microbes in vesicles.
* CD8+ T cells recognize antiges from cytoplasmic bacteria: kill infected cell, thus eliminating reservoir of infection |
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Term
| Evasion of Cell-mediated Immunity |
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Definition
some bacteria and viruses resist effector mechanisms of cell-mediated immunity.
- many intracellular bacteria disrupt phagocytosis
* inhibit fusion of phagosome to lysosome
* create pores in phagosome
- Certain viruses prevent MHC class I antigen presentation
* inhibit production or expression of class I molecules
- Some viruses can produce inhibitory cytokines or decoy cytokine receptors |
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