Encyclopedia of Health and Medicine

274 The Immune System and Allergies
sive, or acquired. INNATE IMMUNITY, also called natural
immunity, is present at birth and provides
effective protection against a broad base of common
pathogens. Innate immunity is limited in
scope. PASSIVE IMMUNITY is ANTIBODY-specific but
present without activation of the IMMUNE RESPONSE.
A newborn has passive immunity based on the
antibodies present in his or her mother’s BLOOD.
BLOOD TRANSFUSION, PLASMA transfusion, and
administration of GAMMAGLOBULIN also convey passive
immunity to the recipient. Passive immunity
is short term. The body develops acquired immunity
through exposure to antigens via infection or
vaccination. Acquired immunity is ANTIGEN-specific
and long term, often lifelong.
For further discussion of immunity within the
context of the structures and functions of the
IMMUNE SYSTEM, please see the overview section
“The Immune System and Allergies.”
See also ANTIBODY-MEDIATED IMMUNITY; CELL-MEDI-
ATED IMMUNITY; PATHOGEN; VACCINE.
immunoablation The therapeutic destruction of
the body’s IMMUNE RESPONSE, typically to prepare
for BONE MARROW TRANSPLANTATION or STEM CELL
transplantation. Immunoablation is usually a step
in the treatment process for certain cancers and
AUTOIMMUNE DISORDERS, such as severe MULTIPLE
SCLEROSIS. High-DOSE CHEMOTHERAPY and RADIATION
THERAPY are the most common methods of
immunoablation. The goal is to remove all T-cell
lymphocytes from the BLOOD, which destroys the
body’s CELL-MEDIATED IMMUNITY. Until the person’s
IMMUNE SYSTEM restores immune functions, the
person is extremely vulnerable to any INFECTION. A
person who has undergone immunoablation stays
in a hospital in strict isolation until immune function
returns after bone marrow or stem cell transplantation.
See also CANCER TREATMENT OPTIONS AND DECISIONS;
LEUKEMIA; MULTIPLE MYELOMA; T-CELL LYMPHOCYTE.
immunocompromised Any circumstance in
which the IMMUNE SYSTEM lacks the capacity, as the
consequence of an acquired health condition or a
medication SIDE EFFECT, to protect the body from
INFECTION. DIABETES is the most common reason
people become immunocompromised. People who
are taking IMMUNOSUPPRESSIVE THERAPY after ORGAN
TRANSPLANTATION or to treat severe AUTOIMMUNE DIS-
ORDERS are also immunocompromised. People who
are immunocompromised often struggle to fight
off common infections such as COLDS and URINARY
TRACT INFECTION (UTI) and are vulnerable to OPPOR-
TUNISTIC INFECTION (an infection that a healthy
immune system would easily rebuff).
See also ANTIBIOTIC PROPHYLAXIS; IMMUNE DISOR-
DERS; LIVING WITH IMMUNE DISORDERS.
immunodeficiency The absence of IMMUNE SYS-
TEM components essential for proper IMMUNE
RESPONSE and protection from INFECTION. Immunodeficiency
may be congenital (present at birth) or
acquired (develop later in childhood or adulthood).
As well, immunodeficiency is a consequence
of therapies intended to compromise
immune function, such as RADIATION THERAPY,
CHEMOTHERAPY, and IMMUNOSUPPRESSIVE THERAPY.
Congenital immunodeficiency is genetic (the
result of a GENE MUTATION) and may be inherited.
Inherited immunodeficiencies can include
IMMUNOGLOBULIN deficiencies, disorders of B-cell
lymphocytes, disorders of T-cell lymphocytes, and
complement disorders. A child born without a
THYMUS or a SPLEEN will have multiple immunodeficiencies
because these structures are crucial for
LEUKOCYTE (white BLOOD cell) formation and maturation.
Acquired immunodeficiency generally occurs as
a result of infections, AUTOIMMUNE DISORDERS, or
severe trauma (such as BURNS) that challenges the
immune system’s capabilities. Conditions such as
DIABETES and CYTOMEGALOVIRUS (CMV) infection
commonly cause immunodeficiency. The HIV/AIDS
infection is one of the most serious acquired
immunodeficiencies, as it eventually destroys the
immune system.
Immunodeficiency disorders are not currently
preventable or curable; diligent treatment can
usually keep disease progression and symptoms in
check. Treatment for immunodeficiency disorders
depends on the cause of the disorder and the
symptoms it creates. Medications and IMMUNOTHER-
APY (biologic response modification) allow many
people who have immunodeficiency disorders live
fairly normal lifestyles.
See also ANTIBODY-MEDIATED IMMUNITY; B-CELL
LYMPHOCYTE; CELL-MEDIATED IMMUNITY; COMMON VARI-