Page 573 - Review of Medical Microbiology and Immunology ( PDFDrive )

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PART VII Immunology
response to the presence of immune complexes deposited
TYPE III: IMMUNE COMPLEX
in many areas of the body. After the injection of foreign
HYPERSENSITIVITY
serum (i.e., serum from another animal such as a horse [or,
Immune complex hypersensitivity occurs when antigen–
more commonly these days, exposure to certain drugs]),
the antigen is excreted slowly. During this time, antibody
antibody complexes induce an inflammatory response in
tissues (Figure 65–3). Normally, immune complexes are
promptly removed by the reticuloendothelial system, but
and antibody leads to the formation of immune complexes,
occasionally they persist and are deposited in tissues, result-
ing in several disorders. In persistent microbial or viral infec- production starts. The simultaneous presence of antigen
Typical serum sickness results in fever, urticaria, arthral-
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tions, immune complexes may be deposited in organs (e.g.,
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gia, lymphadenopathy, splenomegaly, and eosinophilia a
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few days to 2 weeks after injection of the foreign serum or
the kidneys), resulting in damage. In autoimmune disorders,
drug. Although it takes several days for symptoms to
“self” antigens may elicit antibodies that bind to organ anti-
gens or deposit in organs as complexes, especially in joints
tion because symptoms occur promptly after immune
(arthritis), kidneys (nephritis), or blood vessels (vasculitis).
Wherever immune complexes are deposited, they acti-
complexes form. Symptoms improve as the immune system
removes the antigen and subside when the antigen is elimi-
vate the complement system. Polymorphonuclear cells are
nated. Nowadays, serum sickness is caused more com-
attracted to the site, and inflammation and tissue injury
monly by drugs (e.g., penicillin) than by foreign serum
occur. Two typical type III hypersensitivity reactions are
because foreign serum is used so infrequently. A maculo-
the Arthus reaction and serum sickness.
Arthus Reaction
lin, is quite common. Use of antithymocyte globulin
(thymoglobulin), which is made in horses, to provide
Arthus reaction is the name given to the inflammation papular drug-induced rash to penicillins, such as ampicil-
immunosuppression in transplant patients may cause
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caused by the deposition of immune complexes at a localized
serum sickness. Note also that diphtheria antitoxin made in
site. It is named for Dr. Arthus, who first described the
horses is known to cause serum sickness.
inflammatory response that occurs under the following con-
ditions. If animals are given an antigen repeatedly until they
3
have high levels of IgG antibody and that antigen is then
injected subcutaneously or intradermally, intense edema and
Many clinical disorders associated with immune complexes
hemorrhage develop, reaching a peak in 3 to 6 hours.
have been described, although the antigen that initiates the
Antigen, antibody, and complement are deposited in
disease is often in doubt. Several representative examples
vessel walls; polymorphonuclear cell infiltration and intra-
are described next.
vascular clumping of platelets then occur. These reactions
can lead to vascular occlusion and necrosis.
A clinical manifestation of the Arthus reaction is hyper-
sensitivity pneumonitis (allergic alveolitis) associated with Glomerulonephritis
Acute poststreptococcal glomerulonephritis is a well-
accepted immune complex disease. Its onset follows
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the inhalation of thermophilic actinomycetes (“farmer’s
lung”) growing in plant material such as hay. There are
several weeks after a group A β-hemolytic streptococcal
infection, particularly of the skin, and often with neph-
many other occupation-related examples of hypersensitiv-
ity pneumonitis, such as “cheese-worker’s lung,” “wood-
the complement level is low, suggesting an antigen–
worker’s lung,” and “wheat-miller’s lung.” Most of these are
antibody reaction. Lumpy deposits of immunoglobulin
caused by the inhalation of some microorganism, either
and C3 are seen along glomerular basement membranes
bacterium or fungus, growing on the starting material. An
by immunofluorescence, suggesting the presence of
Arthus reaction can also occur at the site of tetanus immu-
antigen–antibody complexes. It is assumed that strepto-
nizations if they are given at the same site with too short an
interval between immunizations. (The minimum interval
is usually 5 years.)
ited on glomeruli, fix complement and attract neutrophils,
which start the inflammatory process.
Similar lesions with “lumpy” deposits containing immu-
Serum Sickness coccal antigen–antibody complexes, after being depos-
noglobulin and C3 occur in infective endocarditis, serum
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In contrast to the Arthus reaction, which is localized
sickness, and certain viral infections (e.g., hepatitis B and
inflammation, serum sickness is a systemic inflammatory
dengue hemorrhagic fever). Lesions containing immune
nephritis of systemic lupus erythematosus, in which the
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Much more antibody is typically needed to elicit an Arthus reaction
“lumpy” deposits contain DNA as the antigen) (see page xx).
than an anaphylactic reaction.
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