Innate Immunity

Question 1

Describe the innate defenses that guard against entry of microbes into body tissues.

Answer 1

Biochemical - sweat, stomach acid, spermine
Commensal Organisms - compete for resources, produce inhibitory substances
Mucus - inhibits adherence to epithelial cells
Mechanical - ciliary action, coughing, flushing by tears, urine, saliva
Epithelia - physical barrier, tight junctions, defensins

Question 2

Distinguish the general characteristics and roles of neutrophils and monocytes/macrophages in innate immunity.

Answer 2

Neutrophils - most abundant, rapid responders, move to extravascular tissue during infection

release cytokines and inflammatory molecules

Monocytes/Macrophages - similar to neutrophils, release cytokines, inflammatory molecules, have APC

Question 3

Describe the general mechanisms by which phagocytes (neutrophils and macrophages) clear microbes.

Answer 3

They bind to multiple cell surface receptors on microbes and phagocytose them. lysosomes filled with reactive oxygen species and nitric oxide fuse with the phagosome.

Question 4

Explain the general characteristics and roles of dendritic cells, mast cells and natural killer (NK) cells in innate immunity.

Answer 4

Dendritic cells - promote inflammation, promote adaptive immune reponse, bridges innate and adaptive by bringing Ag back to lymph tissue

Mast cells - Found in skin filled with proteases and histamine

NK cells - recognizes stressed or infected cells. Secrete INF gamma (activate macrophages). Activated by Interleukin-12 (Activates NK cells and cytotoxic T Cells

Question 5

Describe the general features and functions of the complement system (alternative pathway and lectin pathway) and acute phase proteins in innate immunity.

Answer 5

Soluble proteins that aid in opsonization, cytotoxic, and inflammation. activated via classical, alternative, or lectin pathway.

Acute phase proteins - class of proteins whose plasma concentrations increase or decrease in response to inflammation
----High levels of C-Reactive protein in blood indicates inflammation

Question 6

Explain the principal sources and key functions of major cytokines, including tumor necrosis factor (TNF), interleukin(IL)-1, IL-6, IL-10, IL-12, interferon(IFN)- and type I interferons (IFN- and IFN-) in innate immunity.

Answer 6

TNF - Macrophages, t-cells - causes Fever, neutrophil activation and inflammation
IL-1 - macrophages, endothelial, epithelial cells - causes fever
IL-6 - macrophages, t-cells, endothelial cells - synthesis of acute phase proteins, B-cell proliferation of Ab producing cells
IL-10 - Macrophages, Dendritic cells, T-cells - inhibit IL-12 production
IL-12 - Dendritic cells, macrophages - INF gamma production, increased cytotoxic activity
IFN-gamma - NK cells, t cells, activation of macrophages, stimulation of some Ab response
IFN-alpha - DC’s, macro - antiviral state, increased class I MHC expression, activates NK cells
IFN-beta - fibroblasts - same as INF alpha

Question 7

Explain the general features and functions of the acute inflammatory response.

Answer 7

inflammation increase the permeability of blood vessels to allow proteins to get to the site of infection and recruit leukocytes