MadSci Network: Immunology

Re: how do white blood cells kill microrganisms

Date: Mon May 6 15:31:45 2002
Posted By: Peter Burrows, Faculty, Microbiology
Area of science: Immunology
ID: 1013022104.Im

The white blood cells can eat microorganisms and digest them. The two main 
types of phagocytes (“eating cells”) in your blood are neutrophils and 
monocytes. These cells can also leave the bloodstream and get into the 
tissue if you have an infection, say from a cut on your finger. Phagocytes 
especially like to eat bacteria that have been coated with antibody and 
with another blood protein called complement. Vaccination against 
microorganisms leads to the production of these antibodies. The bacteria 
are then taken inside the phagocytes, which are specialists in killing 
them. The intracellular compartment where the ingested bacteria are 
located is flooded with proteolytic (“protein breaking”) and other enzymes 
which digest the bacterial proteins and cell walls. Another series of 
enzymes are activated and they produce substances which are very toxic to 
the microorganisms including hydrogen peroxide and hypochlorous acid (the 
active component of household bleach). Most microorganisms are killed by 
this powerful combination of enzymes and chemicals, but a few such as 
Mycobacteria, which cause tuberculosis and leprosy, are resistant. 

You can see a movie of phagocytosis at:<

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