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Chemotaxis:
Neutrophils and other leukocytes can sense minute directional
differences in the concentration of chemotactic mediators ("chemotaxins").
The probable reason is that more of their receptors for chemotaxins become
occupied on one side of the the cell, the side nearest the site on inflammation.
Neutrophils respond to chemotactic signals quickly.
In a in vitro experiment, neutrophils complete their chemotactic
response in 90 minutes, mononuclear cells take several hours to complete
their chemotactic response and eosinophils are somewhat intermediate in
chemotactic responsiveness.
Some chemotactic agents are capable of recruiting all
or most of the various leukocyte types. "Chemokines"
are a recently discovered class of chemotactic factors. There is a wide
array of different chemokines with varying potency for attracting different
leukocytes. This allows selectivity in leukocyte recruitment and activation
and helps to explain why some inflammatory responses are primarily eosinophilic,
others are primarily lymphocytic and others contain a mixture of leukocyte
types.
 
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