PHAGOCYTOSIS

Phagocytosis is the process by which some of the cells of our immune system kill and ingest infectious micro-organisms and other 'foreign' matter.

There are 2 main types of phagocytic cells that carry out the process of phagocytosis, namely,

You can think of our phagocytic cells as being the tanks and armoured vehicles of our immune system army, lumbering over the landscape and destroying all 'foreign' cells and organisms that stand in their way.

The diagram below illustrates a process of phagocytosis.

1. The phagocyte comes into contact with a micro-organism by means of opsonins, the phagocytes are affected by opsonins so that micro-organisms adhere to the surface of the phagocytic cell.

2. Once the micro-organism has stuck to the phagocyte, it triggers a phagocyte to throw 'arms' (the real name of these 'arms' is pseudopodia) around the micro-organism, so trapping it and controlling it, following which it can then enclose the micro-organism within its membrane

3. The membrane surrounding the micro-organism fuses with the membrane surrounding the lysosomes in the cytoplasm of the phagocyte - note that a lysosome is a vesicle containing lysosyme and other bactericidal enzymes.

4. The bactericidal enzymes and other toxic molecules found within the lysosomes then kill and digest the micro-organisms inside a phagocytic vacuole (or space within the cell), following which the phagocyte then expels all parts of the ingested micro-organism which it cannot use.

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