Innate Immunity Flashcards
Paradoxically, cell death is needed to initiatie ____.
Paradoxically, cell death is needed to initiatie tissue repair.
The two principal types of reactions of the innate immune system are ____ and ____.
The two principal types of reactions of the innate immune system are inflammation and antiviral defense
high mobility group box protein 1
Histone protein released from necrotic cells and in NETs. Used as a DAMP.
PRR Families
The TLRs
NOD-like Receptors
Sense DAMPs and PAMPs in the cytosol of cells and initiate signaling events that promote inflammation.
NOD2 in Paneth Cells
NOD2 is expressed highly in Paneth cells and, when stimulated, triggers production of antimicrobial defensins and activates NFκB. NOD2 polymorphisms are associated with IBD.
Inflammasomes are composed of. . .
An oligomerized sensor, a signaling platform, and caspase-1.
Most sensors belong to the NLR family, but AIM sensors and pyrin may also oligomerize to activate an inflammasome,
Caspase-1 substrates
pro-IL-1
pro-IL-18
pro-GasderminD
The RIG-like receptors
Cytosolic proteins that sense viral RNA and induce the production of the antiviral type I IFNs.
RLRs recognize features of viral RNAs not typical of mammalian RNA, such as dsRNA and 5’-triphosphate RNA.
Cytosolic DNA sensors
Include several structurally related proteins that recognize microbial double-stranded DNA in the cytosol and activate signaling pathways that initiate antimicrobial responses, including type 1 IFN production and autophagy
Most innate cytosolic DNA sensors engage the ____ pathway
Most innate cytosolic DNA sensors engage the STING (stimulator of interferon genes) pathway. This induces Type I IFN production. STING also stimulates autophagy.
defensins and cathelicidins
Antimicrobial peptides produced by epithelial cells.
Kill bacteria and some viruses by disrupting their outer membranes.
Intraepithelial lymphocytes
Belong to the T cell lineage but express antigen receptors of limited diversity. Made up of αβ and δγ T cells. Often recognize microbial lipids and other structures.
Presumably react against infectious agents that attempt to breach the epithelia, but the specificity and functions of these cells are poorly understood.
Macrophages in adults and during development
Innate lymphoid cells
Tissue-resident cells that produce cytokines similar to those secreted by helper T lymphocytes but do not express T cell antigen receptors (TCRs). The responses of ILCs are often stimulated by cytokines produced by damaged epithelial and other cells at sites of infection. ILCs likely provide early defense against infections in tissues, but their essential roles in host defense or immunological diseases, especially in humans, are not clear.
NK Cell - Macrophage Interaction
Macrophages ingest microbes and produce IL-12, IL-12 activates NK cells to secrete IFN-γ, and IFN-γ in turn activates the macrophages to kill the ingested microbes.
How DCs regulate NK cell activity
Dendritic cells that have encountered microbes enhance the ability of NK cells to protect against infections. These include Type I IFNs, IL-15, and IL-12. IL-15 is important for the development and maturation of NK cells, and type I IFNs and IL-12 enhance the killing functions of NK cells.
antibody-dependent cellular cytotoxicity
The recognition of antibody-coated cells results in killing of these cells
NK Cell Inhibitory Receptors
immunoglobulin-like receptors (KIRs), CD94, and the lectin NKG2. All contain ITIMs.
NK-T cells
Express TCRs with limited diversity and surface molecules typically found on NK cells. They are present in epithelia and lymphoid organs. They recognize microbial lipids bound to a class I MHC–related molecule called CD1.
Mucosal associated invariant T (MAIT) cells
Express TCRs with limited diversity but do not express CD4 or CD8. They are present in mucosal tissues and are most abundant in the human liver, accounting for 20% to 40% of all T cells in that organ. Many MAIT cells are specific for bacterial vitamin B metabolites and likely contribute to innate defense against intestinal bacteria that transgress the mucosal barrier and enter the portal circulation.
B-1 cells
Population of B lymphocytes that are found mostly in the peritoneal cavity and mucosal tissues, where they produce antibodies in response to microbes and microbial toxins that pass through the walls of the intestine. Circulating IgM antibodies found in the blood of normal individuals, even without specific immunization, are called natural antibodies. They are the products of B-1 cells, and many of these antibodies are specific for carbohydrates that are present in the cell walls of many bacteria and for ABO blood group antigens found on red blood cells
marginal-zone B cells
Present at the edges of lymphoid follicles in the spleen and other organs and also is involved in rapid antibody responses to blood-borne polysaccharide-rich microbes.
