Facts on File Encyclopedia of Health and Medicine

Deficiencies in various complement complexes
increase susceptibility to INFECTIONand the risk for
disorders of the immune system. People who have
deficiencies in the preliminary complement cas-
cade 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 BACTERIAthat 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 mecha-
nisms, the pathogens gain advantage in establish-
ing themselves—and infection—within the body.
Other complement deficiencies are common in
SLE and some forms of VASCULITIS (disorders
involving autoimmune INFLAMMATIONof blood ves-
sels). Treatment focuses on the symptoms of the
consequential disorders, notably aggressive antibi-
otic therapy for infection. There are, as yet, no
treatments to correct complement deficiencies.
Doctors recommend meningococcal, pneumococ-
cal, and Haemophilus influenzaeVIRUSvaccinations
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 cas-
cade within the context of the structures and
functions of the immune system, please see the
overview section “The Immune System and Aller-
gies.”
See also ANTIBIOTIC MEDICATIONS; IMMUNE
RESPONSE; MONONUCLEAR PHAGOCYTE SYSTEM; ORGAN
TRANSPLANTATION; PHAGOCYTE; VACCINE.

corticosteroid medications Anti-inflammatory
medications that suppress INFLAMMATIONand 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

BLOODcells 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 cortico-

steroid drugs are either glucocorticoids or a combi-

nation of glucocorticoid and mineralocorticoid.

ALDOSTERONE, another hormone the adrenal cortex

produces, is a mineralocorticoid used therapeuti-

cally as hormone replacement to treat ADDISON’S

DISEASE(a condition in which the adrenal glands

fail). However, aldosterone and other mineralo-

corticoids 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 hyper-

sensitivity reaction, to prevent GRAFT VS. HOST DIS-

EASEin 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 med-

ications are also among the treatment options for

severe asthma and certain other chronic inflam-

matory lung conditions.

It is important to take or use corticosteroid

products correctly, particularly inhalants and nasal

256 The Immune System and Allergies