33 terms
Phagocytosis
non-inflammatory phagocytosis
process in which phagocytic cells engulf cells that die via apoptosis; for maintenance of our own tissue
inflammatory phagocytosis
host defense process mediated by phagocytic cells
antigen presenting cells
internalize pathogens, degrade them into little pieces, and take small peptides and display them on MHC molecules and this is what T-cells recognize.
examples of APCs
macrophages, B-cells, dendritic cells
link from innate immunity to adaptive immunity
action of antigen presenting cells
metalloproteinases
enzymes that chew up collagen and proteins that are involved in junction adhesion to make it easier to move into the surrounding tissue
integrins
involved in pulling the cells through the system/junctions
chemoattraction
mediated by complement molecules, chemokines, and other small molecules which tell cells where to go once they have gotten through the endothelial cell layer
professional phagocytes
neutrophils and monocytes/macrophages
non-professional phagocytes
epithelial and endothelial cells
Fc Receptors and Complement Receptors
essential for efficient phagocytosis
Fc receptors
proteins found on a variety of leukocytes that bind to the Fc portion of antibodies; transduce intracellular signals , Cell-surface receptors for the Fc portion of some immunoglobulin isotypes. They include the Fcγ and Fcɛ receptors.
CR1
complement receptor on phagocytic cells; consists of short consensus repeats; bind to multiple ligands; does not mediate phagocytosis alone - needs help
CR3/4
complement receptor on phagocytic cells; can mediate phagocytosis alone with stimulation; have alpha and beta chains
opsonized antigen
a bacterium that already has antibodies made for it
opsonization
An immune response in which the binding of antibodies to the surface of a microbe facilitates phagocytosis of the the microbe by a macrophage
antigen-->antibody-->
phagocytic cells
stages of phagocytosis
ligand binding, activation of phagocytic cell, engulfment, internalization/fusion with lysosomes, bacterial killing
ligand binding
Fc receptors on leukocytes bind with Fc portion on antibodies (that is bound to antigen)
activation of phagocytic cell
mediated by ligand binding and activation of phagocytic cell through other receptors such as cytokines, LPS, chemoattractants, etc.
engulfment
when phagocytic cell comes in with all of its receptors for different ligands that match the antibodies, it enables the phagocytic cell to zip around the pathogen and internalize it; this process is driven by receptors on phagocytic cell; dramatic change in the cytoskeleton of the cell
internalization/fusion with lysosomes
formation of the phagolysosome, an acidified vesicle suited for pathogen destruction
zipping up process
pseudopodia extend around the pathogen where the selectins and integrins run along the side of the pathogen; involves also actin filaments and myosin for motility and cytoskeletal changes.
Respiratory burst - NADPH Oxidase System
a series of membrane associated enzymes that form free radicals which kill pathogens by disrupting the structure of their proteins
free radicals
superoxide anion, hydrogen peroxide
myeloperoxidase
found in azurophiic granules; mediated generation of HOCl (bleach/Dakin solution) which kill pathogens
enzymes generated by the Respiratory Burst-NADPH Oxidase system
Nitric oxide, myeloperoxidase, superoxide anion, hydrogen peroxide
azurophilic granules
contain elastase, cathespins, lysozymes, meeloperoxidase, and other enzymes that degrade the phagocytosed pathogen
neutrophil extracellular traps (NETs)
when neutrophils are fully activated and have done some phagocytosis, they undergo this process where their nuclear membrane dissolves to release chromatin and granular proteins that form extracellular fibers than bind, trap, and kill bacteria (Gram + and Gram -)
chronic granulomatus disease
genes missing or mutated in the NADPH oxidase system of phagocytosis
chediak-higashi syndrome
membrane trafficking problems, poor fusion of lysosomes and other organelles
clinical presentation of chronic granulomatus disease
recurrent bacterial and fungal infections
clinical presentation of chediak-higashi syndrome
pigmentation abnormalities adn recurrent skin and respiratory infections