Innate Immunity Flashcards
cells of the second line of defense
innate immune cells
processes of non-specific defense
antimicrobial mediators/immune activators
innate immune cells consist of
macrophages, neutrophils, eosinophils, basophils, NK cells, dendritic cells, mast cells
process of non-specific defense consists of
phagocytosis, pattern recognition receptor activation, inflammation
antimicrobial mediators/immune activators consist of
cytokines, interferons, TNF, IL-6; chemokines, complement cascade
cells of innate immunity
granulocytes: contain small granules inside them to provide rapid soluble factor release (eosinophils, basophils, mast cells, neutrophils)
phagocytes: consume and kill pathogens intracellularly, and some participate in adaptive immune engagement (neutrophils, macrophages, dendritic cells)
similar to first line of defense, innate immune cells use _____ _______ to eliminate non-self objects
chemical defense
combination of extracellular and intracellular efficacy provides direct cell killing
neutrophils
-40-60% of leukocytes
-short-lived
-early responders
-work as phagocytes
-granules contain lytic enzymes and antimicrobial peptides
-generates reactive oxygen and nitrogen species (peroxide and hypochlorite)
-form neutrophil extracellular traps
mast cells
-early warning cells that quickly release granules in response to signals from bacteria, viruses
eosinophils
-parasitic infection
-break down outer coating of parasite and kill organisms
macrophages
-monocyte precursors are recruited and differentiate into dendritic cells or macrophages
-phagocytes
-antigen-presenting cells (APCs), stimulate adaptive immune responses
pathogen-associated molecular patterns (PAMPs)
-molecular signatures that are not present in normal mammals
-recognized by pattern recognition receptors (PRRs)
-stimulate an innate immune response, including cytokine and chemokine production
types of PRRs
-toll-like receptors: many ligands
-NOD-like receptors: intracellular bacteria
RIG-I/MDA5: dsRNA
cGAS/STING: cytoplasmic DNA
PKR - dsRNA
innate immunity - phagocytosis
- bacterium binds to PRRs on membrane evaginations called pseudopodia
- bacterium is ingested, forming phagosome
- phagosome fuses with lysosome
- bacterium is killed and then digested by low pH-activated lysosomal enzymes
- digestion products are released from cell
opsonization
enables phagocytosis
-antibodies bind to antigens + complement
-achieves binding with macrophage receptors to achieve phagocytosis
-Fc receptor and C3b receptor (complement fragments)
CHANGES THE SURFACE OF AN ANTIGEN TO ENHANCE PHAGOCYTOSIS
role of antibodies in innate immune activation
-antigen binding
-complement activation
-activate phagocytes and neutrophils for inflammation, opsonization and phagocytosis
multi-component opsonization
-increases the efficacy of innate immune function
- binding through multiple mechanisms increases the effective response
-C3b receptor and Fc receptor
what does the complement pathway do
indirectly triggers inflammation and fever
ways that the complement pathway is activated
classical pathway: antibodies bind to foreign substances and begins the complement cascade, antigen-antibody complexes
alternative pathway: C3 is cleaved, C3b accumulates on a microbe and acts as an opsonin to trigger the complement cascade, spontaneous C3 hydrolysis
lectin pathway: mannose (sugar found on many fungi, bacteria and viruses), binds to lectins and activates complement cascade, MBL-MASP complexes
relationship between innate immune activation and fever
-inhibits growth of some microbes
-many enhance the activities of interferons, phagocytes, cells of specific immunity, and the process of tissue repair
-enhances innate immune activation
process of fever
- chemicals secreted by phagocytes travel in blood to hypothalamus
- hypothalamus secretes prostaglandin, resetting hypothalamic thermostat
- nerve impulses cause shivering, higher metabolic rate, inhibition of sweating, vasoconstriction
- these processes increase body temperature to the point set by the hypothalamic thermostat
role of dendritic cells in connecting innate and adaptive immunity
-link innate and acquired immunity
-professional Antigen presenting cells (APCs)… presents foreign antigen to T cells to induce acquired immune responses
