Phagocytosis Flashcards
What is frustrated phagocytosis?
when the phagocyte runs out of membrane trying to engulf the target
Describe the steps of phagocytosis
- detection (direct = target interacting with receptors; indirect = if target is opsonized then this helps recognition by receptors; chemoattractant cues = activate chemattractant receptors –> movement)
- capture
- phagosome engulfment
- fusion of the phagosome with lysosome –> phagolysosome
- destruction (ROS, iNOS, low pH –> activate enzymes)
- presentation and/or release
What is the phagocytic synapse?
synapse between target and cell membrane
What is a commonality between all phagocytic receptors?
produce intracellular signal –> F-actin rearrangement –> movement or eating
Name four phagocytic receptors, describe if they’re direct/indirect, their type, their expression, and ligands
- mannose receptor: direct, C-type lectin, expressed on M0 and DC, ligand = mannans
- dectin-1: direct, C-type lectin, expressed on M0, ligand = glucose-rich polysaccharides (found on fungi)
- CR3: indirect, integrin, expressed on M0s and PMNs, ligands = iC3b, B-glucans, ICAM-1/2
- FcgRs: indirect, Ig + ITAM, expressed on M0s, PMNs, DCs and NK cells, ligand = IgG
What is the phagocytic code?
R binding –> Tyr kinases –> adaptors –> GEFs –> rho GTPases –> effectors
Why does actin clear at the bottom of the newly formed phagosome?
to let the phagosome sink into the cell
What is % phagocytosis, what are two limitations?
% phagocytosis = how many cells are phagocytosing
limtations: don’t know how many beads per cedll; capture vs phagocytose
Why do we used RBCs to help quantify phagocytosis?
large and red –> easy to see
can tell if they have been engulfed or stuck by lysing the RBCs (macrophages are less susceptible than RBC to hypotonic solutions)
What is the phagocytic index?
a measure of phagocytic activity by counting the number of targets ingested per phagocyte during a limited period of incubation time
