Encyclopedia of Health and Medicine

256 The Immune System and Allergies
Deficiencies in various complement complexes
increase susceptibility to INFECTION and the risk for
disorders of the immune system. People who have
deficiencies in the preliminary complement cascade
pathways that unfold before the formation of
the membrane attack complex are particularly
vulnerable to infections such as MENINGITIS and
PNEUMONIA. Certain of the pathogens that can
cause these infections are encapsulated—viruses
and BACTERIA that enclose themselves in capsules,
or envelopes. The purpose of this encapsulation is
to protect the pathogen against the body’s defense
mechanisms. When defects weaken those mechanisms,
the pathogens gain advantage in establishing
themselves—and infection—within the body.
Other complement deficiencies are common in
SLE and some forms of VASCULITIS (disorders
involving autoimmune INFLAMMATION of blood vessels).
Treatment focuses on the symptoms of the
consequential disorders, notably aggressive antibiotic
therapy for infection. There are, as yet, no
treatments to correct complement deficiencies.
Doctors recommend meningococcal, pneumococcal,
and Haemophilus influenzae VIRUS vaccinations
for people who have complement deficiencies, to
bolster the IMMUNE SYSTEM’s ability to protect
against infections from these pathogens.
For further discussion of the complement cascade
within the context of the structures and
functions of the immune system, please see the
overview section “The Immune System and Allergies.”
See also ANTIBIOTIC MEDICATIONS; IMMUNE
RESPONSE; MONONUCLEAR PHAGOCYTE SYSTEM; ORGAN
TRANSPLANTATION; PHAGOCYTE; VACCINE.
corticosteroid medications Anti-inflammatory
medications that suppress INFLAMMATION and other
aspects of the IMMUNE RESPONSE. Corticosteroid
medications are synthetic variations of the body’s
natural HORMONE CORTISOL, which the ADRENAL
GLANDS produce. Corticosteroids come in
injectable, oral, inhalant, and topical preparations.
How These Medications Work
Corticosteroid medications work by blocking a
number of the pathways in the immune response,
key among them those that produce inflammation.
They suppress the COMPLEMENT CASCADE, activation
of antibodies, and production of eosinophils (white
BLOOD cells that become abundant in a HYPERSENSI-
TIVITY REACTION). Eosinophils are also important for
fighting INFECTION, so suppressing them reduces the
IMMUNE SYSTEM’s ability to mount an effective
defense when infection occurs. Corticosteroids also
act to suppress MAST CELL release of HISTAMINE,
LEUKOTRIENES, and PROSTAGLANDINS—biochemicals
that facilitate inflammation.
There are three general types of corticosteroids,
classified according to how they act in the body:
glucocorticoids, mineralocorticoids, and ANDROGENS
(the sex hormones). Glucocorticoids have the
strongest anti-inflammatory action; most corticosteroid
drugs are either glucocorticoids or a combination
of glucocorticoid and mineralocorticoid.
ALDOSTERONE, another hormone the adrenal cortex
produces, is a mineralocorticoid used therapeutically
as hormone replacement to treat ADDISON’S
DISEASE (a condition in which the adrenal glands
fail). However, aldosterone and other mineralocorticoids
alone have very little anti-inflammatory
action.
CORTICOSTEROID MEDICATIONS
betamethasone
cortisone
desoximometasone
fluticasone
dexamethasone
hydrocortisone
methylprednisolone
mometasone
prednisolone
prednisone
triamcinolone
Therapeutic Applications
Doctors may prescribe corticosteroid medications
to relieve symptoms of moderate to severe hypersensitivity
reaction, to prevent GRAFT VS. HOST DIS-
EASE in bone marrow transplant recipients, and to
treat chronic inflammatory conditions such as
severe OSTEOARTHRITIS, RHEUMATOID ARTHRITIS, ANKY-
LOSING SPONDYLITIS, PSORIASIS, SYSTEMIC LUPUS ERYTHE-
MATOSUS (SLE), and INFLAMMATORY BOWEL DISEASE
(IBD). Corticosteroids in nasal sprays and inhalant
forms are effective treatments for ALLERGIC RHINITIS
and ALLERGIC ASTHMA. Systemic corticosteroid medications
are also among the treatment options for
severe asthma and certain other chronic inflammatory
lung conditions.
It is important to take or use corticosteroid
products correctly, particularly inhalants and nasal