Lewis Triple Response
• Described by sir Thomas Lewis in 1924.
• Lewis
triple
response
is
the
characteristic 3 part response that
develops when a line is made by a
pointed object (a key) on the skin. It is
produced due to the release of
histamine from the mast cells.
• Trauma may release an antigen that interacts with the
membrane-bound immunoglobulin E of mast cells, which release
inflammatory mediators, particularly histamine, into the tissues.
This causes small blood vessels to leak, allowing fluid to
accumulate in the skin.
Inflammatory Response
Components of the Triple Response
1.Red reaction: red line (transient local vasodilation
due to histamine), appears in few seconds.
2.Wheal: localized edema in the region of the redline
(increased capillary permeability and exudation of
fluid from capillaries and venules due to histamine
release), appears in 1 min.
3.Flare: spreading redness extending beyond the red
line (due to axon reflex), appears slowly.
- Three cell types
– smooth muscle in the microcirculation
– endothelium: capillary or venule
– sensory nerve endings
Receptor types
Type
Location
Function
H1
Smooth m.,
endothelium, CNS
Bronchoconstriction, Contraction of GIT,
Vasodilatation
Increased capillary permeability leading to
edema
Pain and itch
H2
Parietal cells, vascular
smooth m.
Vasodilatation, gastric acid secretion
H3
CNS
Modulate the release of other
neurotransmitters
H4
Basophils, BM, Thymus,
spleen
Chemotaxis
Subgroups of Histamine Receptor
Blockers
What will occur with
Antihistamine
OR
Local Anesthetics?