232
P A R T 3
Drugs acting on the immune system
proteins. The lysosomal enzymes are an important part
of biological recycling and the breakdown of once-
living tissues after death. In the case of an inflammatory
reaction, they can cause local cellular breakdown and
further inflammation, which can develop into a vicious
cycle leading to cell death.
Many inflammatory diseases, such as rheumatoid
arthritis and systemic lupus erythematosus, are examples
of these uncontrolled cycles. The prostaglandins and
leukotrienes are important to the inflammatory response
because they act to moderate the reaction, thus prevent
ing this destructive cycle from happening on a regular
basis. Many of the drugs used to affect the inflamma
tory and immune systems modify or interfere with these
inflammatory reactions.
Clinical presentation
Activation of the inflammatory response produces a char
acteristic clinical presentation. The Latin words calour,
tumour, rubor and dolour describe a typical inflamma
tory reaction.
Calour
, or heat, occurs because of the
increased blood flow to the area.
Tumour
, or swelling,
occurs because of the fluid that leaks into the tissues as
a result of the change in capillary permeability.
Rubor
,
or redness, is related again to the increase in blood flow
caused by the vasodilation.
Dolour
, or pain, comes from
the activation of pain fibres by histamine and the kinin
system. These signs and symptoms occur whenever a
cell is injured (Figure 15.2). For example, if you scratch
the top of your hand and wait for about a minute, the
direct line of the scratch will be red (rubor) and raised
(tumour). If you feel it gently, it will be warmer than the
surrounding area (calour). You should also experience a
burning sensation or discomfort at the site of the scratch
(dolour). Invasion of the lungs by bacteria can produce
pneumonia. If the lungs could be examined closely, they
would also show the signs and symptoms of inflamma
tion. They would be red from increased blood flow; fluid
Leukotrienes (LTs)
(LTB
4
, LTC
4
,
LTD
4
, LTE
4
)
Chemotaxis of leucocytes:
Activation of neutrophils
Phagocytosis
Removal of debris
and preparation of
injured site for healing
Prostaglandins (PGs)
(PGI
2
)
Release of arachidonic acid
Release of histamine
Exposure of plasma
to injured cell, etc.
Activation of
Hageman factor
Prekallikrein Active kallikrein
Kininogen Bradykinin
Tissue injury
↑
Blood flow
Calour
(heat)
Rubor
(redness)
Vasodilation
Dolour
(pain)
↑
Capillary permeability
Exudation of
plasma proteins
Oedema
Tumour
(swelling)
FIGURE 15.2
The inflammatory response in relation to the four cardinal signs of inflammation.
