Phagocytosis Immuno Test#1

Chemotaxis,adherance,ingestion,destruction/digestion/killing

Professional phagocytes include basophils, nuetrophils, and eosinophils. they have a very short lifespan but are fast acting. these are also refered to as pmn's or granulocytes bc there cytoplasm is rich with enzyme-like granules. monocytes/macrophages are slow acting and have a much longer lifespan. they are capable of presenting antigens and elliciting a immune response (antigen presentation). monocytes differentiate to macrophages.

Basophils are stained by a basic dye, eosinophils are stained by an acidic dye, nuetrophils are stained by neither a basic nor acidic dye. basophils and eosinophils make up only 3% of the leukocytes and kill extracellularly. neutrophils are the major component with 60-70%. they can kill intracellularly and extracellularly.

Endocytosis or phagocytosis

Process by which cells ingest macromolecules present in the ECF through a process called pinocytosis (cell drinking). this can occur by receptor mediated endocytosis.

A process involving the selective binding of macromolecules to specific membrane bound receptors.

Process by which cells ingest and destroy insoluble particles (bactieria, viruses, fungi, and other pathogens.)

Directed movement of phagocytes through a chemical gradient that can be induced by C5a, chemokines, components of clotting, fibrinolytic, and kinen forming pathways, as well as forgien-derived substances. phagocytes can then move from the blood to the site in the tissue through a process called diapedisis.

A phagocyte must bind the forgien particle once at the site of infection. opsonins bind the forgien substance which enhances their adherence to phagocytes. Cd3 and IgG are the two molecules mainly responsible for opsonization and therefore work synergysically. they each have specific receptors on the phagocytes that when activated cause the phagocyte to ingest and digest the substance at a much faster rate than normally.

As a phagocyte moves towards a forgien particle a pseudopod is extended. when this pseudopod meets the forgien particle it extends around it covering it in cytoplasm. once it is fully engulfed the forgien particle is called a phagosome.

It flows easily over hyrdophobic surfaces and NOT hydrophillic surfaces.dest

Can occur by a respiratory burst, phagosome-lysosome fusion, or toxic nitrogen oxides. the ultimate fate of forgien particles is that the pathogen is broken down into simple amino acids, sugars, and other substances for excretion or to be renuetralized.

When a pathogen is ingested the phagocyte increases its oxygen consumption 4 fold to produce a superoxide dismutase. this superoxide combines with hydrogen to form hydrogen peroxide. hydrogen peroxide then reacts with myeloperoxidase to form hypohalide ion (OCl-). this hypohalide ion reacts with the pathogens proteins, lipids, and nucleic acids killing it.

Lysosomes fuse with phagocytes releasing certain enzymes into them that are either released extracellularly to kill pathogens or are used to kill ingested matieral in the phagocyte.

Lysozymes attack bacterial cell walls. lactoferrin binds and chealates iron which pathogens need to survive so their growth is inhibited. defensin disrupt membrane function and cause osmotic lysis of many pathogens. (some pathogens survive this attack and even actually prefer living intracellularly.)